Herbs & Botanicals · Herbs · Peppermint, taken for tummy trouble

Peppermint

Q: Does peppermint oil help irritable bowel syndrome?

It might help some adults, but the evidence is mixed. Older trials and pooled reviews favour enteric-coated oil for pain and overall symptoms, but the review authors rate the quality very low. The largest recent trials, in 2020 and 2021, did not beat placebo on their main goals, and side effects such as heartburn are more common than with placebo. Talk to a doctor first, because IBS symptoms should be properly diagnosed.

Q: Is peppermint tea as good as the capsules?

There is no evidence that it is. The IBS and indigestion trials tested oil capsules, not tea. Tea has far less oil and no coating. The EU lists tea as a traditional remedy for indigestion and wind, based on long use only, with no trial proof. If you try tea, 1.5 to 3 g of leaf in a cup, up to three times a day, is the EU traditional amount.

Q: Can peppermint cause or worsen heartburn?

Yes. Peppermint relaxes the valve between the food pipe and the stomach, so acid can rise more easily. The EU advises people with reflux to avoid peppermint leaf, and says people with heartburn or a hiatal hernia may get worse from the oil. Heartburn is a commonly reported effect of the capsules even with coating. Stop it if heartburn appears, and see a doctor about chest pain.

Q: Does peppermint oil help headaches?

A 10% oil solution rubbed on the forehead and temples eased tension headache about as well as 1,000 mg of paracetamol in one small 1996 trial of 41 adults. That is the best evidence, and it is thin, old and from one group. For migraine and for teenagers' headaches the evidence is very weak or shows no benefit. Do not use it on children under 18.

Q: Does peppermint help with nausea?

Smelling peppermint oil may lower nausea a little after surgery or with chemotherapy, but the evidence is low certainty, trials are small, and one found that slow breathing alone helped as much. In pregnancy, three small trials disagreed. Ask your midwife or doctor before using it in pregnancy.

Q: How much peppermint oil should I take?

There is no single right amount. The IBS trials used coated capsules of about 180 to 182 mg, two or three times a day, for 4 to 8 weeks. The EU well-established dose is 0.2 to 0.4 ml of oil per coated capsule, up to three times a day, 30 minutes before meals, for up to 3 months a course. The indigestion trials used one 90 mg peppermint and 50 mg caraway capsule twice a day for 4 weeks. Follow the label and do not swallow bottled essential oil.

Q: Is peppermint safe for babies and children?

Not near a baby's face. The EU contraindicates inhaled, mouth and skin peppermint oil and menthol under 2 years because menthol can cause reflex breathing stops and laryngospasm, and NIH says never to put it on the face of infants or young children. Oil capsules are not recommended under 8, and tea not under 4. A 2026 trial found no benefit for children's belly pain. If a baby coughs, goes pale or stops breathing after menthol, call emergency services.

Q: Can I take peppermint in pregnancy or while breastfeeding?

Food amounts are thought to be fine, but medicinal amounts are a question for your midwife or doctor. The EU does not recommend medicinal use of peppermint oil or leaf in pregnancy or breastfeeding because safety has not been established, while NIH says food amounts are likely safe. LactMed notes peppermint has been used to reduce milk supply, and advises applying it to nipples only after nursing and wiping it off before the next feed.

Q: Does peppermint interact with medicines?

Possibly, but the evidence is weak. In 12 healthy volunteers, 600 mg of peppermint oil raised the blood pressure drug felodipine to about 140% of normal exposure, with a wide range from 77% to 262%. In rats it raised cyclosporine levels. Two case reports link menthol cough drops with a lower warfarin INR. Acid reducers and antacids can dissolve the capsule coating early. Ask your pharmacist if you take any of these.

Q: Why does enteric coating matter?

The coating keeps the capsule closed in the stomach so the oil is released lower down, which reduces heartburn and may help it reach the bowel. Chewing or breaking a capsule, taking it with antacids, or taking acid-lowering medicine can open it too early. In a 16-man study coated capsules gave the same total menthol but peaked later (3.0 versus 1.7 hours).

Mentha × piperita L. · also called Peppermint, black peppermint, white peppermint, menta piperita (Spanish), menthe poivrée (French), Pfefferminze (German), hortelã-pimenta (Portuguese)

Peppermint is a sterile mint-family hybrid, believed to be a cross of spearmint and water mint. The leaf is used as a tea, and the oil distilled from the flowering plant is sold as capsules, rubs, inhalers, lozenges and sweets. It is bought mostly for an upset or crampy belly, indigestion, headaches and queasiness. This profile covers peppermint as a herb and supplement. Tea, oil capsules, a skin rub and a food mint are very different things, so a result for one should not be assumed for another. Peppermint is not pennyroyal, a different and dangerous mint.

General information, not medical advice. Last substantive update October 24, 2026 · Not medically reviewed. A named clinician has not signed off on this page. How this page is made

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About Peppermint

Peppermint is a sterile mint hybrid. The leaf is a very common tea and the distilled oil is sold in capsules, rubs and inhalers. It is mainly taken for belly pain, indigestion and headache. The research is mostly on the oil, not the tea. For irritable bowel syndrome the picture is mixed: older trials and pooled reviews favour enteric-coated oil, but the authors rate that evidence very low quality and the largest recent trials, and a 2026 children's trial, did not beat placebo. For indigestion, a peppermint and caraway oil mix was moderately supported in a 2023 Cochrane review (the mix, not peppermint alone). Headache, memory, anxiety and exercise findings are weak, and nothing else is rated above low. The main cautions are heartburn and reflux, allergy to peppermint or menthol, no menthol or peppermint oil near the face of babies under 2, the pulegone limit, some medicine interactions, and mix-ups with pennyroyal.

What it is

Peppermint (Mentha × piperita) is a mint-family (Lamiaceae) plant. It is a sterile hybrid, believed by the EU medicines agency to be a cross of spearmint (Mentha spicata) and water mint (Mentha aquatica). It is grown in many temperate countries for its leaf and its oil.

The leaf is dried for tea. The oil is steam-distilled from the fresh flowering plant and is rich in menthol and menthone. A cup of tea carries only about a fifth to a quarter of the leaf's oil but most of its water-soluble plant chemicals, so tea and oil capsules are not the same thing.

In shops, "peppermint" can also mean other mints or flavourings, so check the Latin name on a label.

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What makes it distinctive

Menthol switches on TRPM8, the cold receptor in nerve cells, which is why peppermint feels cool (lab work, first shown in 2002). In lab tests on gut muscle, peppermint oil and menthol block calcium entry and relax the muscle, which is the usual explanation for its use in cramps. These are test-tube and animal findings at concentrations far above those in blood, so they are proposed explanations, not proof.

Peppermint relaxes the muscle valve between the food pipe and the stomach in older studies quoted by the EU agency, which is one reason it can cause or worsen heartburn. That is why oil capsules are coated to open lower down.

Peppermint also contains small amounts of pulegone and menthofuran, which injure the liver in animals at high doses. Pennyroyal (Mentha pulegium) is a different mint whose oil is far richer in pulegone and has caused fatal poisoning.

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Historical and current uses

Mints were used in Antiquity for flavour and medicine, and peppermint itself was first grown commercially in England around 1750. By 1800 the oil was described as a remedy for nausea, stomach and bowel cramps and wind, and tea has been a popular digestive drink for at least two centuries (EU agency summary of older sources, not checked in the originals).

Today the EU treats peppermint oil in coated capsules as a well-established medicine for minor gut spasm, wind and belly pain, especially in irritable bowel syndrome, and a 10% oil solution on the forehead and temples for mild tension headache in adults. The leaf tea is a traditional medicine for indigestion and wind, based on long use rather than trials.

Peppermint is also used in inhalers and aroma for nausea and tiredness, in lozenges and balms, and as flavouring.

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What the research shows

Irritable bowel syndrome (IBS): a 2022 pooled review of 10 trials (1,030 people) favoured peppermint oil for overall symptoms and pain, with more side effects, but rated the evidence very low quality. A 2019 pooling of 12 trials and a 2014 pooling of 9 trials were also positive. The two largest recent trials were not: 182 mg capsules for 8 weeks in 189 adults (2020) missed the main pain and relief targets, and 180 mg three times a day for 6 weeks (2021) did no better than placebo. A 2026 trial of 228 children also found no benefit. The honest summary is mixed: it may help some adults, but it is not a proven treatment and the placebo effect in IBS is large.

Indigestion: five placebo-controlled trials (578 people) of a fixed peppermint and caraway oil mix favoured the mix in a 2019 review, rated low to very low by its authors, and a 2023 Cochrane review rated the improvement in overall symptoms as moderate certainty, from only a few trials. This tells us about the combination, not peppermint alone.

Headache, thinking, mood and exercise: the single controlled trial of oil on the forehead (1996) is old and small. Memory, alertness and anxiety studies are small, use smells and self-rated scales, and often disagree. Exercise studies are mixed. Evidence is low to very low. Medical-test spasm, nausea, period pain and nipple pain have low-certainty evidence, and nothing else rates above low.

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Root, leaf, powder, extract: what is the difference?

Enteric-coated (gastro-resistant) peppermint oil capsules

Peppermint oil, usually 180 to 182 mg per capsule in the trials, in a capsule coated to open in the intestine and not the stomach. The EU well-established dose is 0.2 to 0.4 ml of oil in a capsule, up to three times a day, 30 minutes before meals, for up to 3 months a course.

This is the form tested for IBS, and the coating is the safety feature: swallow capsules whole, and not with antacids or acid-lowering medicine. A plain, uncoated oil capsule is not what was studied. Different coatings release in different places, and the newest large trials of two designs did not beat placebo.

Peppermint oil plus caraway oil capsule

A fixed coated capsule of 90 mg peppermint oil and 50 mg caraway oil, taken as one capsule twice a day for 4 weeks in the indigestion trials.

This combination is the product behind the moderate-certainty Cochrane rating for indigestion. The effect cannot be credited to peppermint alone, and results do not carry over to tea or to other peppermint capsules.

Leaf tea (infusion)

Dried peppermint leaf steeped in hot water. The EU traditional-use dose for adults is 1.5 to 3.0 g of leaf in 100 to 150 ml of boiling water, three times a day, for indigestion and wind. See a doctor if symptoms last more than 2 weeks; not recommended under 4.

Tea carries far less oil than a capsule and no coating, so it is a different product. We found no placebo-controlled trial of peppermint tea for IBS or indigestion; tea use rests on tradition. The EU advises people with reflux to avoid it. Tea may also lower iron absorption from a meal, so people short of iron may prefer it between meals.

Leaf tincture

Peppermint leaf extracted in 45% or 70% alcohol (1:5). The EU traditional-use dose for adults is 2.0 to 3.0 ml, three times a day.

Traditional use only; no trial was found. The alcohol matters for children, in pregnancy and for anyone avoiding alcohol.

Oil in alcohol rubbed on the forehead and temples

A 10% peppermint oil solution in 90% ethanol, spread on the forehead and temples at the start of a tension headache and repeated after 15 and 30 minutes in the trial.

This is the only skin preparation with a controlled trial (41 adults, 1996). Avoid the eyes and broken skin, and do not use it on children under 18. Stronger or undiluted oil on skin can irritate and cause allergy.

Inhaled oil, inhalers and aroma

Oil breathed from a cloth, inhaler or hot water; about 2% oil or a few drops were used in the nausea trials.

Aroma studies are hard to blind, and many pool several oils, so results are not specific to peppermint. Never use near the face of babies and young children. Do not swallow essential oil.

Lozenges, sweets, mints and menthol products

Peppermint in a lozenge or mint, and pure menthol in cough drops and rubs. The children's trial sweets held 9.2 mg of oil each.

Food mints are not medicines and have a little oil. Menthol is only one part of peppermint oil, and the warfarin case reports involved menthol cough drops, not peppermint tea or oil.

At a glance

Traditional uses history, not proof

Mints were used for flavour and medicine by the Egyptians, Greeks and Romans, according to the EU medicines agency; whether that early mint was the hybrid peppermint is not known
Peppermint was first grown commercially in England around 1750; an 1800 British dictionary describes the oil as easing nausea, spasm pains of the stomach and bowel, and wind (as reported by the EU agency, quoting older sources)
EU traditional use of the leaf tea: indigestion and wind, based on long use only (no trial proof claimed)
EU well-established use of the oil: gastro-resistant capsules for minor gut spasm, wind and belly pain, especially in irritable bowel syndrome; a 10% oil solution rubbed on the forehead and temples for mild tension headache

Studied for research

Irritable bowel syndrome (IBS) in adults, mixed: older and pooled studies favour enteric-coated oil, the largest recent trials missed their main goals
IBS and belly pain in children, mixed, with the biggest and newest trial (2026) finding no benefit over placebo
Indigestion with no clear cause (functional dyspepsia): a fixed peppermint and caraway oil mix, moderate certainty in a 2023 Cochrane review for global symptoms; peppermint alone was not tested
Tension headache (oil on the skin), low certainty; migraine, memory and alertness, tiredness, anxiety and exercise effort: weak or mixed (very low to low)
Nausea after surgery or chemotherapy (smelling the oil), low certainty; period pain, sore nipples, gut spasm during medical tests: low; nothing else rated above low

Main compounds

Menthol (about 30 to 55% of the oil by the pharmacopoeia profile) and menthone: the cooling, gut-relaxing parts; menthol switches on the cold receptor TRPM8 (lab work)
Pulegone and menthofuran: minor oil components that damage the liver at high doses in animals; the EU caps the daily intake from medicines (pennyroyal oil is far richer in them)
Menthyl acetate, 1,8-cineole, limonene and others in the oil
Rosmarinic acid, eriocitrin and luteolin glycosides: water-soluble leaf phenols that make up much of a cup of tea

Common forms

Enteric-coated (gastro-resistant) oil capsules (the form tested for IBS; the coating delays release until the intestine)
Peppermint oil plus caraway oil in one coated capsule (the form tested for indigestion)
Leaf tea (traditional use only; no placebo-controlled trial of tea was found) and leaf tincture
Oil in alcohol for the forehead and temples, inhalers and aroma, lozenges and sweets, and menthol products

Research links: NIH NCCIH: Peppermint oil · EU herbal monograph: peppermint leaf (EMA) · EU herbal monograph: peppermint oil (EMA) · Research Library · Genes & Biomarkers Library

The plant and its history

Accepted scientific name: Mentha × piperita L.
Naming authority: L. (Linnaeus), published in Species Plantarum, page 576 (1753) (GBIF: 'Sp. Pl.: 576 (1753)'; NCBI Taxonomy gives 'Mentha x piperita L.')
Synonyms: Mentha aquatica × spicata; Mentha aquatica f. piperita (L.) G.Mey.; Mentha aquatica var. piperita (L.) Alef.; Mentha aquatica var. langii (Geiger ex T.Nees) Alef.; Mentha glomerata var. piperita (L.) Gray; Mentha hortensis var. citrata Ten.; Mentha officinalis L; Mentha ×balsamea Willd.; Mentha ×crispula Wender.; Mentha ×hircina Hull; Mentha ×langii Geiger ex T.Nees; Mentha ×napolitana Ten.; Mentha ×nigricans Mill.; Mentha ×odora Salisb.; Mentha ×officinalis Hull; Mentha ×pimentum Nees; Mentha piperita (older spelling without the hybrid sign; used in most papers and by NCBI as a synonym)
Common names: Peppermint (English); Black peppermint (English); White peppermint (English); Hairy peppermint (English); Curly mint (English); Menta piperita (Spanish); Menthe poivree (French); Pfefferminze (German); Hortela-pimenta (Portuguese); Pepermunt (Dutch); Pepparmynta (Swedish); Peber-mynte (Danish); Piparminttu (Finnish); Mjata perechnaja (Мята перечная) (Russian); Hujiao bohe (胡椒薄荷) (Chinese)
Botanical family: Lamiaceae (mint family). Older papers, including the EMA report, also write 'Labiatae', which is the older name for the same family.
Classification: Plantae > Tracheophyta > Magnoliopsida > Lamiales > Lamiaceae > Mentha > Mentha x piperita (hybrid)
Native range: The EMA report calls peppermint 'a perennial plant native to Europe' (Ph. Eur. context) and says it was first cultivated commercially in England around 1750. As a sterile hybrid it has no single wild range, and it is grown and naturalised in many temperate countries. A fuller range statement from Plants of the World Online or another flora was not checked.
Habitat: Not verified from a source I read. (General knowledge: damp, fertile ground and gardens; not taken from a cited document.)
What the plant looks like: Roots: Not described in the sources read.; Stems: The EMA report describes a highly aromatic perennial that 'may grow as tall as 90 cm'.; Leaves: The leaf is the part used as tea (whole or cut dried leaf). Oil is made in glandular hairs on the leaf surface: monoterpene (oil) production in peppermint leaves peaks at leaf ages of 12 to 20 days (p10631265), and oil is made and stored in 'peltate glandular trichomes (oil glands)' on the aerial surfaces (p16292524).; Flowers: Not described in the sources read. The steam-distilled oil is made from the fresh aerial parts of the flowering plant (EMA).; Fruit: Not described; the plant is sterile (p16917980).
Cultivation: Commercial peppermint is grown for its oil and leaf. Oil content and make-up change with the plant's age, variety, place and processing (EMA), and with stress: in one pot experiment oil from non-stressed plants was a menthol type (44.6% menthol), whereas lead-stressed or cadmium-stressed plants gave very different oils (linalool/pulegone 32.6/30.8% and menthone/menthyl acetate 30.3/25.1%) (p38285970). Crop acreage and farming practice were not verified.
Harvest and processing: The European Pharmacopoeia defines the dried leaf with at least 12 ml/kg essential oil for the whole drug and 9 ml/kg for the cut drug (Ph. Eur. 0406, quoted in EMA). The essential oil is obtained by steam distillation from the fresh aerial parts of the flowering plant; its Ph. Eur. profile is menthol 30-55%, menthone 14-32%, with a 1,8-cineole to limonene ratio of at least 2 (EMA, citing Ph. Eur. 0405). An infusion carries about 20-25% of the leaf's oil (EMA, citing Duband 1992 and Niesel 1992) and about 75% of the leaf's polyphenols (EMA, citing McKay and Blumberg 2006). Harvest timing and drying practice were not verified.
Look-alikes and adulterants: Name: Spearmint (Mentha spicata L.); Note: One parent of peppermint (GBIF key 2927175; NCBI taxid 29719). Its oil is different: peppermint oil allows at most 1% carvone and is built on menthol and menthone (EMA, quoting Ph. Eur.). That spearmint oil is mainly carvone-rich is general knowledge that I did not verify in a source here. Spearmint tea and peppermint tea are not interchangeable in studies: peppermint IBS and tension-headache evidence is for peppermint oil only.; Name: Water mint (Mentha aquatica L.); Note: The other parent (GBIF key 2927208; NCBI taxid 190902). In one comparison of essential oils, water mint gave 0.69% oil, peppermint 3.73% and horsemint (M. longifolia) 3.21%, and peppermint oil had the strongest antibacterial activity against a multi-resistant Shigella strain (EMA, citing Mimica-Dukic 2003, not checked in the original).; Name: Pennyroyal (Mentha pulegium L.); Note: The important dangerous look-alike. Its oil is rich in pulegone, which is liver-toxic after being turned into menthofuran by the liver; four pennyroyal ingestions were described in one case series (one death) and a review of 18 older cases found moderate to severe toxicity after at least 10 mL of the oil (p8633832; p10220485; p2338648). Peppermint also contains pulegone and menthofuran, but at low levels (pulegone at most 3%, menthofuran 1-8% of the oil, EMA), and EMA accepts a lifetime intake of pulegone plus menthofuran up to 37.5 mg a day for an adult (EMA, public statement EMA/HMPC/138386/2005 Rev. 1, as quoted in the assessment report). GBIF key 2927189; NCBI taxid 294739. Do not substitute pennyroyal for peppermint.; Name: Corn mint, field mint or Japanese mint (Mentha canadensis L., often written Mentha arvensis); Note: GBIF treats Mentha canadensis (key 2927198; NCBI taxid 294733) as the accepted name and lists Mentha arvensis var. piperascens among its synonyms; English vernacular names include 'corn mint' and 'Canada mint'. It is a different species from peppermint. Its role as a source of natural menthol for industry is general knowledge not verified in a source I read, so bottles labelled 'mint oil' or 'menthol' may not come from peppermint.; Name: Other garden mints (for example Mentha x gracilis, Mentha suaveolens, Mentha longifolia); Note: Mentha x gracilis (GBIF key 7923052), Mentha suaveolens (GBIF 2927190) and Mentha longifolia (GBIF 7510173) are accepted in GBIF as separate mints. Mentha longifolia is the species whose genome was sequenced as an ancestor of cultivated mints (p27867107). Hybrid garden mints are numerous, which is why GBIF lists many hybrid names as synonyms of peppermint.; Name: Chinese mint herb (Mentha haplocalyx Briq., 'Herba Menthae'); Note: EMA mentions an extract of Herba Menthae (Mentha haplocalyx Briq., Mentha piperita L.) in an antifungal screen, showing the Chinese drug name has sometimes been matched to peppermint. Treat Chinese-medicine studies on 'bohe' with care: the plant may be a different species.; Name: Chemical variability within true peppermint; Note: Even correctly identified peppermint varies: oil menthol, menthone and pulegone levels move with plant maturity, variety, place and processing (EMA) and with stress (p38285970). This is why Ph. Eur. sets limits and why product labels matter.
Sustainability and conservation: Not verified. Peppermint is a cultivated sterile hybrid, so a conservation status for the hybrid was not looked up.

The plant and the parts used

Close-up of peppermint (Mentha × piperita) leaves — The leaf, used for tea.

Close-up of the whole peppermint plant (Mentha × piperita) — The flowering plant, source of the oil.

Traditional use and history history, not clinical proof

Tradition or era	Documented use	Source
Antiquity: Egypt, Greece and Rome (mints in general)	The EMA review states that in Antiquity 'the Egyptians, Greeks and Romans knew it as flavouring for food as well as for its medical purposes'. The text is about mint in general; the hybrid peppermint is not shown to have existed then, so do not read this as proof of ancient peppermint tea.	s-ema-ar-mentha-piperita-2020
England, 1600s to about 1750 (John Ray herbarium; first commercial cultivation)	EMA says one of the oldest specimens of the spearmint x water mint hybrid is in the herbarium of the English botanist John Ray (1628-1705), and that peppermint was first cultivated commercially in England around 1750, with the aerial parts the most used for medicine (citing Murray 1972, not checked in the original).	s-ema-ar-mentha-piperita-2020
Britain, 1800 (English Dictionary of Medicinal and Surgical Knowledge)	Peppermint oil was described as 'an aromatic stimulant to allay nausea, relieve spasmodic pain to the stomach and the bowels, expel flatus' and to cover the taste of harsh medicines (EMA, citing Jones 1981 via Kline 2001; not checked in the original). EMA also calls peppermint a popular digestive remedy for at least the last two centuries.	s-ema-ar-mentha-piperita-2020
Britain, 1900s (Bradley 1992, British Herbal Compendium; British Herbal Pharmacopoeia 1983)	Leaf infusion (one or two teaspoons, 1.5-3.0 g, in 8 ounces of water, three times a day) or tincture (1:5, 45% ethanol; 2-3 mL three times a day) for dyspepsia, wind, intestinal colic and bile-duct complaints; oil in small doses (0.02-0.08 mL, 1-4 drops in dilute water preparations) for digestive complaints (EMA tables 2a and 2b).	s-ema-ar-mentha-piperita-2020
Germany, 1985-1990 (Commission E, Blumenthal)	Official German advice: 3-6 g of cut leaf a day as tea, or 5-15 g of 1:5 tincture (70% ethanol), for spasms of the digestive tract and of the gallbladder and bile ducts; oil 6-12 drops a day for spasm of the upper digestive tract and bile ducts, irritable colon, catarrh of the airways and inflamed mouth lining (Blumenthal 1998) (EMA tables 2a and 2b).	s-ema-ar-mentha-piperita-2020
Europe, 2000s (ESCOP monograph 2003; WHO monograph on Menthae piperitae folium 2002)	ESCOP and WHO list leaf infusion 1.5-3 g in 150 mL of water three times a day before meals for dyspepsia, flatulence and intestinal colic, with ESCOP giving children's daily infusion amounts by age (4-10 years, 3-5 g; 10-16 years, 3-6 g). For oil ESCOP gives 0.2-0.4 mL three times a day in enteric-coated capsules for irritable bowel syndrome and 5-20% semi-solid or oily preparations for outside use (muscle and nerve pain, coughs and colds) (EMA tables 2a and 2b).	s-ema-ar-mentha-piperita-2020
Modern science, 1980s-1990s	Laboratory work in the late 1980s and early 1990s showed that peppermint oil and menthol block calcium entry into gut muscle cells and relax gut muscle in isolated tissue (p2856502, p1646142), the first explanation for its use in irritable bowel syndrome. Enteric-coated capsules were developed because oil released in the stomach relaxes the lower oesophageal sphincter and can cause heartburn (EMA; p11455677). (Source for the sphincter and heartburn point: EMA, s-ema-ar-mentha-piperita-2020.)	p2856502
2002 onward: the cold-and-menthol receptor	In 2002 two groups cloned the TRPM8 channel as the receptor for both menthol and cold (p11882888, p11893340); in 2007 mice lacking it were shown to have a strongly reduced ability to detect cold (p17538622). This turned folk knowledge that peppermint 'feels cool' into a defined receptor mechanism.	p11893340
Modern European regulation (EMA/HMPC, assessment report revision 1, final January 2020)	EMA's assessment (EMA/HMPC/522409/2013) treats peppermint leaf as a traditional herbal medicine for digestive complaints such as dyspepsia and flatulence, backed by literature showing use over about 30 years; peppermint oil is assessed for 'well-established use' (symptom relief in irritable bowel syndrome and minor spasms, wind and abdominal pain; cream or solution on the forehead and temples for mild tension-type headache) and for traditional use by inhalation and on the skin (coughs and colds, muscle pain, itching), which clinical studies do not support (EMA conclusions, pp 95-97). Whether the oil's EMA status page still shows an 'ongoing call for scientific data' was not checked.	s-ema-ar-mentha-piperita-2020

Traditional use shows how a plant was used. It does not show that a supplement works or is safe today.

What is inside, and how it may work

What the plant contains and how those compounds act in cells and animals. Laboratory and animal mechanisms are not proven effects in people.

Main compounds

Compound	Family	Where it is concentrated	Activity studied	Level of evidence
Menthol ((-)-menthol) PubChem 16666	cyclic monoterpene alcohol	Essential oil (leaf glandular hairs) 30-55% of peppermint oil (Ph. Eur., quoted in EMA). In one human study, 100 mg given as a capsule was measured as menthol glucuronide in blood (p10460066).	Opens the cold-and-menthol receptor TRPM8 in cells and is the receptor that makes menthol feel cool (p11882888; p11893340; p17538622). Switches on TRPA1 at low concentrations and blocks it at higher ones (cells; p17855602). Blocks calcium entry through L-type channels in animal gut muscle (about twice as potent as the whole oil per weight, p2856502). Blocks serotonin 5-HT3 receptor channels in cells and rat gut (p21077259). Inhibits human CYP3A4 in test tubes (Ki 87 micromolar, p12235445). In rats, high topical doses reduced pain responses to heat and cold (p20398704). Biosynthesis from limonene takes eight enzyme steps in the oil glands (p16292524). CID 16666 is the (-)-isomer; CID 1254 is menthol without stereochemistry. ^{90 110 14 62 48 49 36 24 70 22 153 156}	Mixed
Menthone PubChem 26447	cyclic monoterpene ketone	Essential oil 14-32% of peppermint oil (Ph. Eur., quoted in EMA).	Principal companion of menthol in the oil (McKay and Blumberg call menthol and menthone the main volatile components). No separate activity data were read. ^{89 153}	Insufficient
Isomenthone PubChem 6432469	cyclic monoterpene ketone	Essential oil 1.5-10% of peppermint oil (EMA).	No separate activity data read. CID shown is the racemic isomenthone in PubChem. ¹⁵³	Insufficient
Neomenthol PubChem 439263	cyclic monoterpene alcohol	Essential oil Named with menthol, menthone and isomenthone as a main oil component by a 2022 review (p35994817); no percentage verified.	In nasal inhalation tests in 40 volunteers, L-menthol made airflow feel more open, but its isomers D-isomenthol and D-neomenthol did not (Eccles 1988, as described in EMA, not checked in the original). CID 439263 is (+)-neomenthol; other neomenthol forms have other CIDs. ^{150 153}	Human data
Menthyl acetate PubChem 27867	monoterpene ester	Essential oil 2.8-10% of peppermint oil (EMA).	A reversible inhibitor of human liver CYP3A4 in test tubes (Ki 124 micromolar, p12235445). No other activity read. ^{24 153}	Laboratory research
1,8-Cineole (eucalyptol) PubChem 2758	monoterpene ether	Essential oil 3.5-8% of peppermint oil; Ph. Eur. requires a cineole to limonene ratio of at least 2 (EMA).	No peppermint-specific activity data read. In EMA, cineole was tested with peppermint, jasmine and menthol on attention (no significant result, Ilmberger 2001, not checked in the original). ¹⁵³	Insufficient
Limonene PubChem 22311	cyclic monoterpene	Essential oil 1-3.5% of peppermint oil (EMA).	The first committed step in menthol biosynthesis: peppermint cyclises geranyl diphosphate into (-)-(4S)-limonene, which the later enzymes convert to menthol (p16292524). CID 22311 is limonene without stereochemistry; (+)-limonene is CID 440917 and the peppermint pathway makes the (-)-form. ^{22 153}	Laboratory research
Menthofuran PubChem 329983	furan-type monoterpene	Essential oil 1-8% of peppermint oil (EMA).	A liver-toxic metabolite of pulegone; further oxidised by human liver enzymes (CYP2E1, CYP1A2, CYP2C19, CYP2A6) to a reactive furan epoxide and a gamma-ketoenal that bind to liver proteins (p10220485; p1581528; p2338648). Safety limits are set for pulegone plus menthofuran, not for either alone (EMA). ^{68 137 136 38 153}	Laboratory research
Pulegone ((R)-(+)-pulegone) PubChem 442495	monoterpene ketone	Essential oil At most 3% of peppermint oil (EMA); the main constituent of pennyroyal oil (p10220485).	Turned into menthofuran by human CYP2E1, CYP1A2 and CYP2C19 (p10220485); depletes glutathione and is liver-toxic in rats (p2338648). In a human pennyroyal series, 18 ng/mL pulegone and 1 ng/mL menthofuran were found in serum 72 hours after a fatal ingestion (p8633832). EMA accepts up to 37.5 mg a day of pulegone plus menthofuran for an adult (public statement quoted in EMA). ^{68 136 9 38 153}	Mixed
Carvone PubChem 7439	monoterpene ketone	Essential oil At most 1% of peppermint oil (EMA). CID 7439 is carvone without stereochemistry.	Peppermint oil/caraway oil capsules were studied together, so carvone is measured as the caraway marker in that product (p11455677). No peppermint-specific activity. ^{84 153}	Insufficient
Rosmarinic acid PubChem 5281792	phenolic acid (caffeic acid ester)	Leaf (water-soluble) Measured in commercial peppermint tea infusions together with eriocitrin and luteolin glycosides; one tea bag infusion delivered up to 182.2 mg of total polyphenols (p18052102). A 40-clone study quoted by EMA put eriocitrin at 6.6-15.0% (units not stated in EMA) with rosmarinic acid accompanying it.	Listed as a main leaf phenolic (p16767798; p37959863). Antioxidant in test tubes, not shown to have a benefit from tea in people (McKay and Blumberg: clinical trials of peppermint tea are absent, p16767798). No peppermint-specific human blood levels were read. ^{33 89 56 153}	Laboratory research
Eriocitrin (eriodictyol 7-O-rutinoside) PubChem 83489	flavanone glycoside	Leaf (water-soluble) The dominant phenolic in a 40-clone study (6.6-15.0%, EMA, units not stated); measured by HPLC in commercial peppermint teas (p18052102).	Antioxidant in test tubes; high in the cultivar with the greatest total phenols (EMA, citing Dorman 2003, not checked in the original). No human activity data read. ^{33 153}	Laboratory research
Luteolin and its glycosides (luteolin, luteolin 7-O-glucoside, luteolin 7-O-rutinoside, luteolin 7-O-glucuronide) PubChem 5280445	flavone and flavone glycosides	Leaf Luteolin 7-O-rutinoside and luteolin 7-O-beta-glucuronide were measured in tea infusions; the glucuronide and lithospermic acid were reported as new compounds for Mentha x piperita (p18052102). CIDs: luteolin 5280445; luteolin 7-O-glucoside 5280637 (C21H20O11). Luteolin 7-O-rutinoside was not found by name in PubChem, so no CID is claimed for it.	Luteolin 7-O-rutinoside reduced an antigen-induced nasal response in rats at 100 and 300 mg/kg, and a leaf extract blocked histamine release from rat mast cells (Inoue 2001, as summarised by EMA; animal). Flavonoids from the leaf relaxed isolated guinea-pig gut and increased bile flow in dogs (EMA, older studies). ^{33 153}	Animal research
Hesperidin PubChem 10621	flavanone glycoside	Leaf Named with eriocitrin and luteolin as a main leaf flavonoid (p16767798); no content figure verified.	No peppermint-specific activity data read. ^{89 56}	Insufficient
Menthol glucuronide (body metabolite, not in the plant) PubChem 71749954	glucuronide conjugate of menthol	Made in the body from menthol The only form of menthol found in human blood and urine after oral menthol (p10460066).	The main bile metabolite, which is recycled between gut and liver (enterohepatic circulation) (p16121523). Measuring it in blood is how peppermint-oil release is tracked in people (p30284674; p34528282). ^{36 40 147 127 105}	Human data

Mechanisms, receptors and pathways

Target or pathway	Gene or receptor	What was found	Level
Cold and menthol receptor (menthol)	TRPM8	Menthol activates TRPM8, a channel in cold-sensing nerve cells, and cold (below about 26 C) does too; this is why menthol feels cool (p11882888, p11893340, p17538622). Mice lacking TRPM8 had strongly reduced cold responses but still avoided surfaces below 10 C (p17538622). In rats, high-strength menthol on the skin (10-40%) reduced avoidance of cool temperatures and prolonged the response to heat, but 40% also made touch more painful, and low strengths (0.01-1%) increased cold avoidance, a two-way effect (p20398704). EMA describes trigeminal nerve stimulation in the nose by L-menthol in 40 volunteers and a lasting cool sensation on the skin, plus reduced pain sensitivity in 32 volunteers after a 10% oil-in-ethanol solution was put on the forehead (Gobel 1995); those human studies were not read in the original. ^{90 110 14 70 153}	Mixed
Pain and irritant receptor (menthol)	TRPA1	Low to moderate menthol (sub-micromolar to low-micromolar) opened human TRPA1 in cells and higher concentrations blocked it; the authors suggest this adds to menthol's varied skin and mouth sensations (p17855602). Only cell and nerve-cell work; no peppermint-tea or capsule evidence. ⁶²	Laboratory research
Gut muscle: calcium entry through L-type channels	L-type voltage-gated calcium channel (gene not named in the papers; CACNA1C/Cav1.2 is the usual smooth-muscle form, which is background knowledge, not tested here)	Peppermint oil and menthol blocked calcium-dependent contraction in guinea-pig gut, with menthol about twice as potent as the oil (IC50 about 8-28 micrograms/mL in gut muscle) and competed with a dihydropyridine blocker for binding (p2856502). Patch-clamp work on rabbit gut muscle cells showed peppermint oil reduced the calcium current in a way resembling dihydropyridine drugs (p1646142). In 255 human gut tissue pieces from 73 surgical patients, peppermint oil relaxed muscle (IC50 17-90 micrograms/mL), the effect did not depend on nerves, and the contraction-reducing effect was prevented by the L-type channel activator Bay K8644 (p31612595). The authors of the first study say calcium blockade may not be the only effect. ^{48 53 72}	Laboratory research
Serotonin 5-HT3 receptor channel	5-HT3 receptor (the subtype is a receptor channel; the gene or subunit was not specified in the paper)	Peppermint oil and (-)-menthol reduced ion flow through 5-HT3 channels in a mouse nerve-cell line and reduced serotonin-triggered contraction of rat ileum, without displacing a standard 5-HT3 blocker, so they probably act at a different site on the channel (p21077259). EMA also notes non-competitive block of serotonin- and substance-P-triggered contraction in animal gut (Hills 1991, p1646142). Not tested in people. ^{49 53}	Laboratory research
Gut and bile-duct relaxation in people	none identified	EMA summarises small human studies where peppermint oil instilled in the stomach or colon relaxed muscle within about 30 seconds and for up to about 23 minutes, and a pharmacology study (90 mg with caraway oil) that relaxed the gallbladder and slowed small-bowel transit (EMA, not read in the original). A 2020 meta-analysis of six colonoscopy studies found less spasm, severe spasm and peristalsis with peppermint oil (risk differences -0.39, -0.15 and -0.27), but with large differences between studies (p31994371). These show a real gut-relaxing effect for the oil, not proof of which receptor causes it. ^{13 20 153}	Human data
Lower oesophageal sphincter (heartburn)	none identified	Oral peppermint oil (15 drops in 30 mL of water) relaxed the muscle valve between stomach and gullet and allowed reflux in a 1969 study quoted by EMA (not read in the original). EMA and a 2018 review tie heartburn, the commonest side effect in trials, to oil being released too early in the upper gut, which enteric coating aims to prevent (p29372567; p11455677). ^{20 84 153}	Human data
Bile flow (choleretic) effect	none identified	Peppermint tea (0.4 g/kg) raised bile secretion in dogs; leaf flavonoids and menthol did the same in dogs and rats (EMA, older Russian, French and German studies, not read in the original). Whether this matters for people is not established; EMA says people with gallstones and bile-duct disorders should be cautious. ¹⁵³	Animal research
Visceral pain sensitivity	none identified (modulation by TRP channels is suggested by reviewers)	In rats given a gut irritant, 14 days of peppermint plus caraway oil reduced the pain-related muscle response by up to 50%, though neither oil alone had a significant effect (Adam 2006 as described by EMA, not read in the original). A 2018 review lists TRP-channel effects on visceral sensitivity among several possible mechanisms for irritable bowel syndrome relief (p29372567). ^{153 20}	Animal research
Germs: bacteria, fungi and viruses	none identified (no single target)	In the lab, peppermint oil and leaf extracts slowed growth of several bacteria and fungi and cut herpes simplex virus counts in cell culture (oil at 0.01% reduced HSV-1 by 82% and HSV-2 by 92%, acting on the virus before it enters cells) (EMA, citing Schuhmacher 2003, not checked in the original). Gram-positive bacteria were more sensitive than Gram-negative in a 2023 review (p37959863). A leaf extract had a MIC50 of 100 micrograms/mL against Helicobacter pylori in a screening study (EMA, citing Mahady 2005). Everything here is test-tube or cell work; no human infection trial of peppermint was read, and oil strength in tests is far above what blood levels would reach. ^{56 150 153}	Laboratory research
Liver enzyme and transporter interactions (CYP3A4, P-glycoprotein)	CYP3A4; CYP1A2 and CYP2E (rat); P-glycoprotein	Peppermint oil (Ki 35.9 micrograms/mL), menthol and menthyl acetate inhibited human liver CYP3A4 in test tubes. In 12 healthy volunteers, 600 mg of peppermint oil with felodipine raised felodipine's blood exposure (AUC) to 140% of water (range 77-262%, P<0.05) (p12235445). EMA notes another menthol study (n=11) found no marked change in felodipine and that a rat study found tea cut CYP1A2 and CYP2E activity (24% and 48%) and that peppermint oil tripled the peak cyclosporine level in rats (EMA, not read in the originals). A small crossover study with huge individual variation. ^{24 153}	Mixed
Pulegone and menthofuran: how they injure the liver	CYP2E1, CYP1A2, CYP2C19, CYP2A6; glutathione	Human liver CYP2E1, CYP1A2 and CYP2C19 convert pulegone to menthofuran, then to a reactive furan epoxide and gamma-ketoenal (p10220485; p1581528). In rats pulegone used up liver glutathione, and the harm was worse when glutathione was blocked (p2338648). These toxicity data come from pennyroyal-type exposures and doses far above normal peppermint tea; they explain why EMA caps pulegone plus menthofuran (p25512112; p8633832). ^{68 137 136 38 9}	Mixed
Leaf flavonoids: antioxidant and allergy-type effects	none identified	Peppermint leaf had a high oxygen-radical absorbance in test-tube assays (EMA), and a leaf extract blocked histamine release from rat mast cells and reduced sneezing in a rat allergy model (EMA, citing Inoue 2001, not read in the original). No human trial of peppermint tea for allergy or inflammation was read. ^{153 56}	Animal research
Overall caution	n/a	The best-supported effects are the gut-relaxing action of peppermint oil and the cooling action of menthol. Randomised trial results in irritable bowel syndrome are mixed: pooled earlier trials are positive (for example the 2008 meta-analysis of four trials, p19008265), newer larger trials are not clearly positive (see studies). Cell and animal concentrations are often much higher than blood levels in people. Peppermint tea has no controlled-trial support for most uses (p16767798). ^{67 8 58 148 103 89 34}	Insufficient

Absorption, metabolism and elimination

Absorption: Peppermint oil is absorbed fairly quickly by mouth and cleared mostly through bile, per a review of animal work (p16121523). In 16 healthy men, 180 mg of peppermint oil (with 100 mg caraway oil) as enteric-coated or immediate-release capsules gave similar total menthol exposure (90% CI of the AUC ratio 97-105%) but later peaks with the enteric-coated form (about 3.0 hours versus 1.7 hours); mean peak menthol levels were 1196 ng/mL (enteric) and 1492 ng/mL (immediate release) (p11455677). In 8 healthy volunteers, 182 mg of standard small-intestine-release oil peaked at a median of 180 minutes and an ileocolonic-release capsule at a median of 360 minutes (menthol glucuronide measured), with a delay before it started of 37 versus 225 minutes (p30284674). In 30 children aged 7-12 with abdominal pain, menthol exposure rose in line with dose across 180, 360 and 540 mg of enteric-coated oil (p34528282). EMA cites animal dermal absorption of oil with a lag of about 58 minutes in mice, and a lung half-life for inhaled menthol of about 35 minutes (not read in the originals).
Distribution: No human tissue-distribution data for oil components were found in the sources read.
Metabolism: Menthol is turned into menthol glucuronide: after a 100 mg menthol capsule, or 10 mg in mint sweets or tea, only the glucuronide could be measured in human blood and urine (12 volunteers) (p10460066). In rats, other urinary metabolites are hydroxylated menthols and carboxylic acids, some also conjugated with glucuronic acid (p16121523; EMA). The liver enzyme(s) that glucuronidate menthol in people were not identified in the sources read. Pulegone is converted to menthofuran by human CYP2E1, CYP1A2 and CYP2C19 (p10220485).
Elimination: Menthol glucuronide had a plasma half-life averaging 56.2 minutes after the capsule (95% CI 51.0-61.5) and 42.6 minutes after sweets or tea (32.5-52.7); urine recovered 45.6% and 56.6% of menthol as the glucuronide (p10460066). In children taking enteric-coated oil, the half-life of menthol exposure averaged 2.1, 3.5 and 4.6 hours at 180, 360 and 540 mg (p34528282), so values depend on formulation. Bile is the main route and the glucuronide is recycled through the gut (enterohepatic circulation) (p16121523). In rats excretion was about equal in faeces and urine (p16121523). A prodrug study (rat gut contents, human stool) found menthol glucuronide stable at pH 4.5-7.4 but broken down by colon contents (more slowly in human stool than in rat), and about 20% broken down in 4 hours at pH 1.5, which is why the authors concluded enteric coating would be needed (p7899232).
Bioavailability: Not established for individual oil components. Pure menthol and menthol in food or drink had similar systemic bioavailability in 12 volunteers (p10460066). The release site matters: enteric coating delays but does not reduce total menthol exposure (p11455677), and a distal-release capsule delayed the peak further with a small, significant drop in the AUC (median 2331 versus 2623 micrograms h/L) in 8 volunteers (p30284674). Peppermint tea: EMA quotes work (Hurrell 1999, not checked in the original) in which peppermint tea cut absorption of non-haem iron by 84% compared with water in a bread meal, at about the same level as black tea at higher polyphenol doses. Drug interactions: see CYP3A4 in mechanisms (p12235445).

^{84 147 127 36 40 105 68 24 153}

Isolated compounds versus whole extracts

Peppermint is used in three different ways, and the evidence does not carry across them. (1) Enteric-coated peppermint oil capsules are the form tested for irritable bowel syndrome; the oil delivers menthol and other monoterpenes together, and menthol alone is about twice as strong as the oil by weight in a lab muscle test (p2856502). (2) Leaf tea is mostly water-soluble phenols: about 75% of the leaf's polyphenols reach the infusion but only 20-25% of its oil (EMA), and no controlled trial of peppermint tea was found by McKay and Blumberg (p16767798). A tea bag can deliver up to 182.2 mg of polyphenols (p18052102). (3) Pure menthol on its own: in 12 volunteers a 100 mg menthol capsule gave a menthol glucuronide level about 9 times that of 10 mg in sweets or tea, with similar fractions recovered in urine (p10460066), showing that tea contains little menthol compared with a medicinal dose. Pure menthol also changes heart rate slightly and reduced a 'vigor' score at 30 minutes (p10460066). In the lab, menthol alone mimics the oil's calcium-channel and 5-HT3 effects, but the oil also contains menthyl acetate and other compounds that inhibit CYP3A4 (p12235445). Practical point: results from enteric-coated oil capsules, a cup of tea, a menthol rub and the diluted oils in cosmetics are not interchangeable, and pulegone and menthofuran, which are low in peppermint, are the main components of pennyroyal oil.

Nutritional composition

A nutrient table is not meaningful for peppermint: it is used as dried leaf for tea, as a flavouring, or as an oil, not as a food that supplies vitamins or minerals in useful amounts. The leaf contains palmitic, linoleic and linolenic fatty acids in its non-polar fat fraction (EMA, citing McKay and Blumberg 2006), phenolic acids and flavonoids (see compounds), and small amounts of triterpenes (EMA). No vitamin or mineral content was verified and none is claimed here. One nutrition fact is documented: peppermint tea, like other polyphenol-rich herb teas, strongly lowered absorption of non-haem iron from a bread meal in radio-labelled studies (peppermint tea 84% lower than water; black tea 79-94%, pennyroyal tea 73%, chamomile 47%) (EMA, citing Hurrell 1999; not checked in the original). People who need to protect their iron stores may do better drinking it between meals.

Products, quality and comparisons

Independent evidence comes first. Nothing in this section is a paid ranking. If a product link is added later, it will be marked clearly as an affiliate link and will never change what the research says.

Quality indicators

Plant named as Mentha x piperita, with the part stated (leaf for tea; oil from the aerial parts)
For oil capsules: mg of oil per capsule, and a statement that the capsule is enteric-coated / gastro-resistant (delayed release)
Where it is meant to release (small intestine or colon) if the maker claims it
Menthol and menthone content, and pulegone and menthofuran limits, from a certificate of analysis
Ingredients listed separately (caraway oil, fennel, other herbs), not hidden in a blend
Lot number and certificate of analysis on request
Seal or registration checked on the certifier's or regulator's own website

Identity and authenticity

We did not find a published survey of peppermint oil or peppermint tea adulteration in our searches, so we make no claim about how common it is.
Because oil is a high-value product, buyers can ask the maker for a certificate showing the oil meets a pharmacopoeia standard.

Standardization and extract strength

The European Pharmacopoeia sets the standard for peppermint oil (the 2007 EMA draft says the material must comply with it). A secondary source (an Estonian chemistry journal, 2004) lists menthol 30 to 55% and menthone 14 to 32%; we did not read the pharmacopoeia itself, so treat these as unverified.
EMA's 2016 statement, using Ph. Eur. 8.1 limits, calculates that 1.2 ml of oil (1,099 mg) holds at most 32.97 mg pulegone and 87.92 mg menthofuran. That is a ceiling of about 3% pulegone and 8% menthofuran.
EMA limit for pulegone plus menthofuran: 0.75 mg per kg body weight a day for lifelong use (37.5 mg a day for a 50 kg adult), or 75 mg a day for under one year. Pulegone is liver-toxic in animals at high doses; EMA reports no confirmed human liver damage from peppermint oil, mint oil or peppermint leaf preparations, and notes under-reporting cannot be excluded. Pennyroyal oil is far richer in pulegone and is the main concern.
Peppermint oil, mint oil from Mentha canadensis, and pennyroyal oil are different products with different limits; check the label names the species.

Certifications and what they actually mean

Certification	What it means	What it does not tell you

Extract types compared

Extract	Plant part	Standardization	Trials	Evidence note	Safety note	Limitations	Studies
Small-intestinal-release peppermint oil, 182 mg	oil	Not in abstract	Weerts 2020 (189 adults with IBS, 8 weeks); Vermeijden 2026 (182 mg capsules in 228 children, 8 weeks)	Adults: main goals missed, secondary pain outcomes positive. Children: no benefit over placebo.	Mild adverse events, more common than with placebo in adults.	Frequency of dosing in adults not in abstract.	^{148 141}
Ileocolonic-release peppermint oil, 182 mg	oil	Not in abstract	Weerts 2020	No benefit on main or secondary goals as reported; authors do not support further development.	More mild adverse events than placebo.	One trial.	¹⁴⁸
Enteric-coated peppermint oil, 180 mg three times a day	oil	Not in abstract	Nee 2021 (6 weeks)	No difference from placebo; both groups improved.	Not in abstract.	Single centre; sample size not in abstract.	¹⁰³
Sustained-release small-intestine peppermint oil capsule	oil	Not in abstract	Cash 2016 (72 adults, 4 weeks)	Total symptom score fell 40% vs 24.3% with placebo.	Well tolerated, few adverse events (per abstract).	Industry-linked author; small.	¹⁹
Colpermin enteric-coated delayed-release capsule	oil	Not in abstract	Liu 1997 (110 adults, 1 month); Merat 2010 (90 adults, 8 weeks)	Both positive for abdominal pain over placebo.	No significant liver test changes in Liu 1997; no significant adverse reaction in Merat 2010. One heartburn case (chewed capsules).	Older trials; mg per capsule not in the abstracts.	^{78 95}
Mintoil enteric-coated capsules	oil	Not in abstract	Cappello 2007 (57 adults, 4 weeks)	75% vs 38% with a more than 50% symptom fall.	Not in abstract.	Small; patients with other causes excluded.	¹⁸
Peppermint oil 90 mg + caraway oil 50 mg (Enteroplant) and Menthacarin	oil + caraway fruit oil	Not in abstract	May 2000 (96 patients); Madisch 1999 (118, vs cisapride); Freise 1999 (223, dose comparison); Rich 2017 (114, Menthacarin)	Positive vs placebo in two trials; equivalent to cisapride in one; Cochrane 2023 rates global symptom improvement as moderate-certainty.	Adverse events similar to placebo in pooled data (NNH 40 in Li 2019).	Combination; cannot assign effects to peppermint alone.	^{87 81 35 116 76 17}
10% peppermint oil in ethanol (LI 170)	oil	10 g oil per 100 ml	Gobel 1996 (41 patients, 164 headache attacks)	Better than placebo and about as good as 1,000 mg acetaminophen.	No adverse events reported.	One small trial; 1996.	⁴³

Compare Peppermint with another ingredient

Compare with

Peppermint vs Ginger

Both are used for stomach and gut complaints but no trial compares them. Peppermint oil has far more trials for IBS; the ginger evidence read here is one small study of gastric emptying that did not change symptoms.

	Peppermint	Ginger
Benefits studied	IBS pain and global symptoms; functional dyspepsia (with caraway oil); tension headache (topical); nausea (inhaled)	Gastric emptying in functional dyspepsia (small trial); nausea (not compared here)
Evidence certainty	Low to moderate for IBS (reviews rate very low quality); moderate for the peppermint-caraway mix in dyspepsia (Cochrane 2023)	Very-low: the one trial read had 11 people and no symptom change
Typical studied dose	IBS capsules: about 180 to 182 mg per dose, three times a day in the trials that state it, for 4 to 8 weeks	1.2 g ginger in capsules, single dose
Head-to-head trial	None found	None found against peppermint
Safety and interactions	Heartburn, peppermint-tasting burps; acid-lowering drugs can dissolve the coating early; avoid with gallstones and bile disorders unless advised	Not re-verified here; see the ginger profile
Forms	Enteric-coated capsule, tea, tincture, topical oil, inhaled	Capsule, tea, fresh root
Cost note	Use the price-per-day formula; no prices stored	Use the same formula

^{55 58}

Peppermint vs Fennel

Fennel oil appears in a single positive IBS trial as part of a curcumin combination, so its own effect is unknown. Peppermint oil has more and larger trials, though mixed.

	Peppermint	Fennel
Benefits studied	IBS, dyspepsia, headache (topical)	IBS symptoms (fennel essential oil combined with curcumin)
Evidence certainty	Low to moderate (see ginger row)	Low: one 121-patient trial of a curcumin plus fennel oil combination; Hawrelak 2020 says it has not been replicated
Typical studied dose	IBS capsules: about 180 to 182 mg per dose, three times a day in the trials that state it, for 4 to 8 weeks	Curcumin plus fennel oil, 2 capsules twice a day for 30 days (mg per capsule not in abstract)
Head-to-head trial	None found	None found
Safety and interactions	See quality and safety notes in this section	Not re-verified here
Forms	Capsule, tea, tincture, topical, inhaled	Essential oil capsule in the trial; seed tea traditionally
Cost note	Use the price-per-day formula	Use the same formula

^{112 47}

Peppermint vs Chamomile

Chamomile is a common companion herb in gut formulas (including STW 5) but we could not find a trial of it on its own for these conditions, so no real comparison is possible.

	Peppermint	Chamomile
Benefits studied	IBS, dyspepsia	We found no randomised trial of chamomile alone for IBS or dyspepsia in our search
Evidence certainty	Low to moderate	Insufficient: no trial read
Typical studied dose	IBS capsules: about 180 to 182 mg per dose, three times a day in the trials that state it, for 4 to 8 weeks	Not available
Head-to-head trial	None found	None found
Safety and interactions	See safety notes	Not re-verified here
Forms	Capsule, tea, tincture	Tea, extract; chamomile is one ingredient of STW 5
Cost note	Use the price-per-day formula	Use the same formula

⁹⁴

Peppermint vs STW 5 (Iberogast-type herbal mix)

STW 5 is a multi-herb liquid that contains peppermint among its plants; peppermint-caraway oil capsules have more consistent dyspepsia results in the Cochrane review. No head-to-head trial exists.

	Peppermint	STW 5 (Iberogast-type herbal mix)
Benefits studied	IBS, dyspepsia	Functional dyspepsia, IBS
Evidence certainty	Mixed. Pooled reviews (Ingrosso 2022: 10 RCTs, 1,030 patients, RR of not improving 0.65, NNT 4) favour oil over placebo, but authors rate quality very low and the 2020 and 2021 trials did not meet main goals; dyspepsia (with caraway oil) moderate	Dyspepsia: very low to low in Cochrane 2023 (global symptoms MD -2.64, 5 studies, very low); IBS: positive in one 208-patient trial (Madisch 2004)
Typical studied dose	IBS capsules: about 180 to 182 mg per dose, three times a day in the trials that state it, for 4 to 8 weeks	Dose not in the abstracts read
Head-to-head trial	None found	None found against peppermint oil
Safety and interactions	See safety notes	Adverse events similar to placebo in pooled data; a 2022 case report links Iberogast to acute liver injury (abstract only; cause not established)
Forms	Enteric-coated capsule, tea	Liquid herbal mix of several plants including peppermint leaf and chamomile
Cost note	Use the price-per-day formula	Use the same formula

^{94 82 17 58}

Peppermint vs Low-FODMAP diet (context, not a herb)

They can be used together; the diet has the stronger guideline support in the ACG abstract, while peppermint oil has an official European traditional-use listing and mixed trial results.

	Peppermint	Low-FODMAP diet (context, not a herb)
Benefits studied	IBS pain and global symptoms	IBS global symptoms, pain, bloating
Evidence certainty	Mixed. Pooled reviews (Ingrosso 2022: 10 RCTs, 1,030 patients, RR of not improving 0.65, NNT 4) favour oil over placebo, but authors rate quality very low and the 2020 and 2021 trials did not meet main goals	Low certainty in the 2025 network meta-analysis (24 trials: RR of global symptoms not improving 0.51, 95% CI 0.37 to 0.70); ACG 2021 recommends a limited trial
Typical studied dose	IBS capsules: about 180 to 182 mg per dose, three times a day in the trials that state it, for 4 to 8 weeks	A restriction phase then reintroduction, guided by a dietitian (not detailed in the abstract)
Head-to-head trial	None found	None found
Safety and interactions	Heartburn, side effects more often than placebo	Diet is restrictive; best done with a dietitian
Forms	Capsule	Diet plan
Cost note	Capsule cost	No product cost

^{23 73 58}

Peppermint vs Antispasmodic drugs (otilonium, hyoscine; context)

In Ford 2008 both beat placebo, with peppermint oil showing the larger relative effect in only four trials. The review is from 2008, before the larger null trials, and there is no direct comparison.

	Peppermint	Antispasmodic drugs (otilonium, hyoscine; context)
Benefits studied	IBS pain and global symptoms	IBS pain and global symptoms
Evidence certainty	Peppermint: RR of persistent symptoms 0.43 (4 trials, 392 patients) in Ford 2008	Antispasmodics as a group RR 0.68 (22 trials, 1,778 patients); otilonium 0.55; hyoscine 0.63 (Ford 2008)
Typical studied dose	IBS capsules: about 180 to 182 mg per dose, three times a day in the trials that state it, for 4 to 8 weeks	Prescription doses (not in the abstract)
Head-to-head trial	None found	None found against peppermint oil
Safety and interactions	Heartburn; acid-lowering drugs can dissolve coating	Drug side effects not covered in the abstract; ask a clinician
Forms	Capsule	Tablet (prescription)
Cost note	Use the formula	Prescription price

^{34 58}

Other supplements people compare it with

Low-FODMAP diet trial (IBS): Recommended by the 2021 ACG guideline as a limited trial; a 2025 network meta-analysis found the low FODMAP diet improved global symptoms (RR of not improving 0.51), with low-certainty comparisons. Evidence: low. ^{73 23}
Antispasmodic drugs (otilonium, hyoscine) (IBS pain): Ford 2008 meta-analysis: RR of persistent symptoms 0.68 for 22 trials; ask a clinician. Evidence: moderate. ³⁴
Gut-directed psychotherapy (IBS): The ACG 2021 guideline suggests it (statement seen in the abstract; certainty rating not read). Evidence: low. ⁷³
STW 5 (Iberogast-type liquid) (Functional dyspepsia, IBS): Cochrane 2023: very low to low certainty for dyspepsia; positive in one IBS trial. Evidence: low. ^{17 82 94}
Curcumin plus fennel oil (IBS): One 121-patient trial positive over 30 days; not replicated per Hawrelak 2020. Evidence: low. ^{112 47}
Ginger (Dyspepsia): One small crossover trial: faster gastric emptying, symptoms unchanged. Evidence: very-low. ⁵⁵
Acetaminophen (paracetamol) (Tension-type headache): In the 1996 crossover trial 1,000 mg worked about as well as 10% peppermint oil on the skin. Evidence: low. ⁴³

Where to buy

Check the label first. Whatever you buy, look for these:

The plant part and the extract type or ratio on the label
A standardized amount of the active compounds, where relevant
A third-party testing mark (USP, NSF or ConsumerLab)
Interactions: ask a pharmacist if you take medicines, are pregnant or have a medical condition

Talk to a pharmacist or doctor before you start any supplement, especially if you take medicines. See the Safety tab for interactions.

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21benefits and uses looked at

157studies and sources checked

Low certaintybest evidence rating found

16lab markers tracked in trials

6 mixed findings8 low certainty5 very low certainty2 not enough evidence

What was looked at

The 21 benefits and uses checked for Peppermint, each with how strong the evidence is. Tap one to open it.

Tension-type headache (oil on the forehead and temples)Low certainty
Migraine attacks (nose drops or menthol gel)Very low certainty
Chronic headache in teenagers (aroma during a foot bath)Not enough evidence
Alertness, memory and focus (smelling or swallowing the oil)Mixed findings
Fatigue and sleepiness (aroma)Low certainty
Anxiety and stress (aroma before procedures)Very low certainty
Confusion (delirium) after hip or knee surgery in older adultsVery low certainty
Exercise effort and performance (oil, aroma, menthol rinse)Mixed findings
Irritable bowel syndrome (enteric-coated oil)Mixed findings
Belly pain in children (IBS and functional abdominal pain)Mixed findings
Functional dyspepsia (upper belly pain and fullness)Low certainty
Oesophageal spasm: chest pain and trouble swallowingVery low certainty
Colon spasm during colonoscopyMixed findings
Gut spasm during upper endoscopy, ERCP and barium X-raysLow certainty
Nausea after surgery (smelling peppermint oil)Low certainty
Nausea from chemotherapy (inhaled or dabbed on)Low certainty
Nausea and vomiting in pregnancyMixed findings
Bowel recovery after Caesarean section (mint drops)Not enough evidence
Period pain (primary dysmenorrhoea)Low certainty
Sore, cracked nipples while breastfeeding (applied to skin)Low certainty
Itch (applied to skin)Very low certainty

Lab markers tracked in the studies

Headache pain intensityCognitive task performanceRated fatigue and sleepinessPupil fatigue oscillation (sleepiness index)EEG alpha/beta ratio (driving fatigue)Rated anxiety and stressHeart rate and blood pressure (during anxiety trials)Postoperative delirium (3 days)Time to exhaustionPerceived effort (RPE) and thermal sensationColonic spasm score during colonoscopyTime to reach the caecum during colonoscopyAdenoma detection rate at colonoscopyTime for gastric contraction rings to disappear at endoscopySimultaneous contractions of the food pipeTime to first bowel sound and first gas after surgery

What is Peppermint good for?

The main proposed uses and how strong the human evidence is for each. "Moderate" is the best rating any peppermint use reached, and only for a peppermint and caraway mix in one 2023 review. "Mixed" means trials disagree. "Low", "very low" and "insufficient" mean few, small or inconsistent trials. Nothing here is a proven treatment, and the ratings are this profile's reading of the reviews, not formal grades unless stated. Most uses are for the oil, not for tea.

Irritable bowel syndrome in adults (enteric-coated oil)Mixed findingsOlder and pooled results say coated peppermint oil helps belly pain and overall symptoms. A 2022 review of 10 trials (1,030 people) found it better than placebo for overall symptoms (about 1 in 4 more people helped) and for pain, but the authors rated the evidence very low quality and side effects were more frequent. The largest recent trials missed their main goals: 189 adults (2020) did not beat placebo on pain or relief, and a 2021 US trial found no difference at all (the placebo group improved as much). Heartburn is the commonest side effect. Plain tea was not tested for IBS. Belly pain and IBS in childrenMixed findingsA 2026 trial of 228 children aged 8 to 18 found peppermint oil capsules and peppermint sweets worked no better than placebo (treatment success 44.0% on the oil, 37.3% on placebo). A small 2001 trial of 42 children had reported less pain in 75% on the oil. The newest and largest trial is the stronger evidence, and it does not support a benefit. Indigestion with no clear cause (peppermint plus caraway oil)Moderate certaintyA fixed capsule of 90 mg peppermint oil with 50 mg caraway oil, taken twice a day for 4 weeks, beat placebo in several trials and matched the older drug cisapride in one. A 2023 Cochrane review rated the improvement in overall symptoms as moderate certainty, while a 2019 review of five trials rated the evidence low to very low. This is the combination. Peppermint oil alone, and peppermint tea, were not tested for indigestion. Tension headache (10% oil rubbed on the forehead and temples)Low certaintyIn a 1996 crossover trial of 41 adults, 10% peppermint oil in alcohol eased tension headache about as well as 1,000 mg of paracetamol, and better than placebo. It is the best-supported mind-related use, but the trial is old, small and from one research group, with no recent independent repeat. The EU advises it only for adults. Migraine attacks (nose drops or menthol gel)Very low certaintyOne trial of 120 adults found 1.5% peppermint oil nose drops helped about as well as lidocaine drops and better than placebo, and a small open trial of menthol gel saw some relief. The evidence is weak, and the products are not standard. Peppermint oil is not proven for migraine. Long-term headache in teenagers (aroma in a foot bath)Not enough evidenceAdding peppermint oil to a relaxing foot bath did not reduce pain or anxiety more than the foot bath alone in teenagers. The relaxation itself helped. Alertness, memory and tiredness (smelling or swallowing the oil)Mixed findingsStudies disagree. Some small controlled studies found better memory or attention and less mental fatigue after smelling the oil or taking it in a capsule, one found no effect on a vigilance task, and a 2025 review of smell studies could not reach a firm conclusion. Tiredness fell in several small trials (including 105 heart patients), but results are mostly self-rated and peppermint was not shown to beat lavender or other scents. Anxiety and stress (aroma before procedures)Very low certaintySmelling peppermint oil lowered anxiety scores in a few small hospital trials, but it was weaker than lavender in children and added nothing when mixed with lavender. The evidence is thin. Confusion (delirium) after hip or knee surgery in older adultsVery low certaintyIn one 2025 trial of 178 older adults, smelling peppermint oil after joint replacement went with less delirium in the first three days (7.9% versus 19.1%). It is a single borderline result that needs repeating. Exercise effort and performance (oil, aroma, menthol rinse)Mixed findingsSome small studies, several by one author, reported longer time to exhaustion or stronger performance after swallowing the oil, while other studies found no effect. In runners it did not make effort feel easier, and menthol mouth rinses and gels did not clearly improve performance. Nausea after surgery or chemotherapy (smelling the oil)Low certaintyA 2024 review of aroma treatments found less nausea after surgery (low certainty), and a 2026 trial of 106 women found nausea or vomiting in 52.8% with peppermint oil versus 73.6% with saline. Older trials were mixed, and one found that just breathing slowly helped as much. For chemotherapy, a few small trials suggest the smell can lower nausea alongside usual drugs, but the studies are few and use different methods. A 2018 Cochrane review of all aromatherapy oils together found no clear drop in nausea severity. Nausea and vomiting in pregnancyMixed findingsThree small trials disagreed. Peppermint oil alone matched placebo in two of them, and a lemon and peppermint blend helped from day 2 in one. The evidence is weak and mixed. Medicinal use in pregnancy is not recommended by the EU agency, so ask a midwife or doctor first. Colon spasm during colonoscopyMixed findingsStudies are split. Peppermint oil put into the colon through the scope by the doctor tends to reduce spasm. Capsules taken by mouth beforehand helped in one trial and not in two others. A 2020 pooled review found less spasm but results varied a lot. This is a medical-procedure use, not a home use. Gut spasm during upper endoscopy, ERCP and barium X-raysLow certaintyIn several studies, peppermint oil put into the stomach or bowel by the doctor, or mixed with barium, reduced muscle spasm about as well as injected antispasmodics, with fewer side effects such as dry mouth. The trials are older, small to moderate and not all randomised. Spasm of the food pipe (chest pain, trouble swallowing)Very low certaintyA very small test (8 people) and a chart review (38 people) suggest peppermint oil may relax spasm in the food pipe and ease chest pain or swallowing trouble in some. Neither had a placebo group. Chest pain should always be checked by a doctor. Period painLow certaintyA small crossover trial of 127 students found peppermint capsules lowered period pain and its length, like mefenamic acid, though bleeding fell less. A 2025 review of five trials (499 women) also found less pain and asked for better studies. Sore, cracked nipples while breastfeeding (applied to skin)Low certaintySeveral trials from similar settings found peppermint water or gel on the nipples prevented cracks and eased pain, better than lanolin or breast milk in two, though one trial found no difference from lanolin or dexpanthenol cream. Apply only after nursing and wipe off before the next feed, as the LactMed database advises. Itch (applied to skin)Very low certaintyTwo small trials found peppermint oil on the skin eased itch in people with liver, kidney or diabetes-related itch and in pregnant women, compared with petrolatum or a placebo oil. Bowel recovery after Caesarean section (mint drops)Not enough evidenceOne trial of 102 women found mint drops brought back bowel sounds and gas sooner. It is a single study, and its abstract says mint, not peppermint.

Benefits, one by one

Each card is a research question, not a promise. Tap a goal to filter. Open a card to see the studies, doses and limits.

Tension-type headache (oil on the forehead and temples)

Low certainty

A 10% peppermint oil in alcohol, rubbed on the forehead and temples, eased tension headache about as well as 1,000 mg of paracetamol in one small controlled trial from 1996. It is the best-supported mind-related use of peppermint, but the evidence is thin, old and mostly from one research group.

3 studies10% peppermint oil in 90% ethanol, applied thinly on forehead and tem…

Studies, doses and limits

What the trials found

Göbel 1996: 41 adults with tension-type headache treated 4 attacks each in a double-blind crossover (164 attacks). 10% peppermint oil in ethanol, spread on the forehead and temples and repeated at 15 and 30 minutes, lowered headache intensity versus placebo from 15 minutes (p<0.01) for the full hour. 1,000 mg acetaminophen also beat placebo (p<0.01), with no difference between the two. Using both together added a little but not significantly. No side effects were reported. Göbel 1994 tested the same kind of preparation in healthy volunteers and found reduced sensitivity to experimental pain. Göbel 2016, a narrative review by the same clinic, says the oil is licensed for adults and children over 6 in some countries and is regarded as standard acute therapy; those claims are the authors' own and were not independently checked.

Results

Peppermint oil lowered tension-headache pain within 15 minutes versus placebo in the one controlled trial found; effect comparable to paracetamol 1,000 mg.

Effect sizes as reported

No effect sizes in the abstracts; p<0.01 for oil vs placebo at all time points reported.

Why this rating

One small crossover trial (41 people, 1996) with abstract-only reading, plus a review by the same group. No independent replication or recent large trial found in this search; the later review's claim of guideline status is not verified here.

Form and dose studied

10% peppermint oil in 90% ethanol, applied thinly on forehead and temples and repeated at 15 and 30 minutes (Göbel 1996). Do not copy this with other strengths or undiluted oil.

Who was studied

Adults 18 to 65 with episodic tension-type headache.

Limits

Only one adult trial; no data on frequent or chronic tension headache or prevention; headache diary self-report; commercial test product; skin and eye irritation possible.

Why researchers looked

Tension headache is the most common headache, and a cheap, topical, drug-free option is attractive.

Traditional use

Peppermint is a traditional folk remedy for head and temple discomfort in Europe (stated as general background, not verified in this file).

Proposed mechanism Preliminary mechanism

Menthol, the main compound, activates cold-sensing nerve receptors (TRPM8) in the skin. This is thought to give a cooling and numbing effect and may relax tense muscles. A 1994 test in healthy volunteers found a peppermint-ethanol preparation reduced sensitivity to experimental headache-type pain. How this works for real headaches is not proven.

A proposed mechanism does not show that the effect happens in people.

Peppermint oil on the skin can irritate; see the safety file for who should avoid it (for example, young children). No adverse events were reported in the headache trial.

^{43 42 44}

Migraine attacks (nose drops or menthol gel)

Very low certainty

Menthol or peppermint oil on the skin or in the nose has been tried for the pain of a migraine attack. One randomised trial found nose drops of 1.5% peppermint oil helped about as well as lidocaine drops, and a small open pilot of menthol gel saw some relief. The evidence is weak, and rat work shows menthol can also stimulate pain pathways.

4 studiesPeppermint essential oil 1.5% nose drops (not a standard product); me…

Studies, doses and limits

What the trials found

Rafieian-Kopaei 2019: 120 adults with migraine were given 4% lidocaine nose drops, 1.5% peppermint oil nose drops or placebo; headache intensity differed between groups (P<0.001) and roughly 40% of the lidocaine and peppermint patients improved considerably, more than placebo. St Cyr 2015: 25 completers applied 6% menthol gel to the skull base within 2 hours of onset in an open pilot with no placebo; 28% had no pain at 2 hours but 12 took rescue medicine before 24 hours. Lopresti 2020 (19 randomised herbal trials, nine herbs) called menthol/peppermint oil preliminary positive for acute treatment but noted high risk of bias in many studies.

Results

Some pain relief in an attack in two small studies; no placebo-controlled replication; reviewers call it preliminary.

Effect sizes as reported

Nose drops: about 41-42% 'considerable responders' (as stated in the abstract) vs fewer with placebo; gel: 28% pain-free and 56% mild or none at 2 hours in an open pilot.

Why this rating

Two small studies of different products (essential oil nose drops, menthol gel), one without a placebo; a systematic review saying the evidence is preliminary with high bias risk; animal data pointing both ways. Not a formal GRADE rating.

Form and dose studied

Peppermint essential oil 1.5% nose drops (not a standard product); menthol 6% gel applied to the skull base. Neither is a dosing recommendation.

Who was studied

Adults with episodic migraine.

Limits

Small studies; unclear placebo response in the gel pilot; nasal essential-oil drops are not a regulated product and may irritate; no trial on preventing migraines.

Why researchers looked

Migraine is disabling and many people look for non-drug options to use during an attack.

Traditional use

Cooling and aromatic applications to the head are an old folk practice (stated as general background, not verified in this file).

Proposed mechanism Animal research

Menthol activates the cold receptor TRPM8, which is also present in pain-sensing nerves of the head. The effect may be helpful (cooling-linked pain relief) or harmful. In rats, menthol placed directly on the brain's covering tightened blood vessels at 5% and 10% but made pain-signalling neurons fire more at 1% and 30%, which the authors read as TRPM8 activation being pro-headache (Sokolov 2024).

A proposed mechanism does not show that the effect happens in people.

Nasal use of essential oil may irritate (general caution, see the safety file). Migraine with new or severe symptoms needs a doctor.

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Chronic headache in teenagers (aroma during a foot bath)

Not enough evidence

In a trial of teenagers with long-term headaches, adding peppermint oil to a relaxing foot bath did not reduce pain or anxiety more than the foot bath alone. The relaxation itself helped.

1 studiesPeppermint oil added to a brief foot bath (amount not stated in the a…

Studies, doses and limits

What the trials found

Kingsley 2023: 46 adolescents (mean age 15.2; 89% female) with a primary headache disorder were randomised to a brief foot bath or a foot bath with peppermint oil. Both groups reported less pain and less anxiety over the session; the oil group did not improve more on pain, and anxiety fell slightly more in the oil group (p=0.03). Pain actually kept falling in the plain foot-bath group while it levelled off in the oil group.

Results

Both groups felt better; the extra peppermint added no clear pain benefit.

Effect sizes as reported

p-values only; pain: no significant added benefit of peppermint; anxiety difference p=0.03.

Why this rating

One small, single-session trial in 46 people with no added pain benefit, short follow-up, and a mixed anxiety result.

Form and dose studied

Peppermint oil added to a brief foot bath (amount not stated in the abstract).

Who was studied

Adolescents with chronic primary headache.

Limits

One session; no long-term outcomes; dose unknown; female-dominated.

Why researchers looked

Few treatments are tested in young people with chronic headache, and parents look for gentle options.

Proposed mechanism Pharmacological theory

No mechanism was tested in this trial; the authors framed the foot bath as a way to trigger the body's relaxation response.

A proposed mechanism does not show that the effect happens in people.

No adverse events; well tolerated and liked by 95.5%. See the safety file for use in young children.

⁶⁹

Alertness, memory and focus (smelling or swallowing the oil)

Mixed findings

Studies on whether peppermint sharpens the mind are mixed. Two controlled studies found better memory or attention and less mental fatigue, one found no effect on vigilance, and a 2025 review of the smell studies says no firm conclusion can be drawn yet.

6 studiesAroma (amount mostly not given); or 50 to 100 microlitres of the oil …

Studies, doses and limits

What the trials found

Moss 2008: 144 healthy volunteers were assigned to peppermint aroma, ylang-ylang aroma or none; peppermint improved memory and raised alertness. Kennedy 2018: 24 healthy adults took 50 or 100 microlitres of the oil in a capsule; the higher dose improved a sustained-attention task at 1 and 3 hours and both doses reduced fatigue and improved a subtraction task at 3 hours. Heuberger 2010: peppermint inhalation did not improve a vigilance task. Norrish 2005: peppermint limited the rise in measured sleepiness in a dark room. Sullivan 1998: peppermint scent brought false alarms in people with brain injury down to the level of controls on a long attention test. Nishi 2025, a scoping review of 8 inhaled-peppermint studies, found the studies too varied to conclude.

Results

Positive in several small lab studies (memory, attention, less mental tiredness), null in one, and no firm overall conclusion in the 2025 review.

Effect sizes as reported

No pooled effect sizes; individual abstracts give p-values or direction only.

Why this rating

Small, single-session lab studies with different outcomes, some positive and one null; the review calls a conclusion premature. No trials in people with memory problems or dementia were found in this search.

Form and dose studied

Aroma (amount mostly not given); or 50 to 100 microlitres of the oil in a capsule, single dose (Kennedy 2018; a research dose, not advice).

Who was studied

Healthy adults, mostly young; one study of people with brain injury.

Limits

Single sessions; short-term; many tests per study; expectation effects from a recognisable smell; swallowed essential oil should not be copied at home.

Why researchers looked

Peppermint is a popular stimulating scent and people use it for studying and long work days.

Traditional use

Mint has long been used as a refreshing herb (general background, not verified in this file).

Proposed mechanism Laboratory research

Peppermint oil bound to nicotine-type and GABA-A receptors and slowed the enzyme that breaks down acetylcholine (an AChE inhibitor) in lab tests, and raised calcium in neuron-like cells (Kennedy 2018, lab screening). Smell could also act through expectation and the pleasantness of the scent. The mechanism is not proven in people.

A proposed mechanism does not show that the effect happens in people.

Swallowing neat essential oil can burn the mouth and gut; use only products made for swallowing.

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Fatigue and sleepiness (aroma)

Low certainty

Several small trials in which people smelled peppermint report less tiredness, in cardiac patients, in people with mental exhaustion and in a driving test. Most results come from self-rated scales and single hospitals, and the blends or comparison scents make peppermint's own part hard to judge.

5 studies3 drops inhaled nightly for 7 nights (cardiac trial); personal inhale…

Studies, doses and limits

What the trials found

Mahdavikian 2021: 105 cardiac patients inhaled 3 drops of peppermint or lavender oil, or a placebo scent, for 7 nights; fatigue fell in both oil groups versus placebo (P<0.001) with no difference between them. Varney 2013: 14 people with mental exhaustion used an inhaler of peppermint, basil and helichrysum oils versus rose water; both fell in burnout but the oil group fell much more. Jiang 2024: peppermint, grapefruit or lavender scent all reduced rated and EEG-measured fatigue in a driving task versus control; peppermint was not shown to be better. Kennedy 2018 (above) also saw less mental fatigue after the oil capsule. Norrish 2005 showed a smaller rise in objective sleepiness with the smell.

Results

Fatigue and sleepiness scores improved with peppermint in small trials, but so did other scents, and the studies are short.

Effect sizes as reported

Between-group P<0.001 in the cardiac trial; other studies give direction only.

Why this rating

Only a few small trials with self-rated scales; a smell that participants can recognise cannot be hidden from them; blends and other scents muddle peppermint's own effect. Not a formal GRADE rating.

Form and dose studied

3 drops inhaled nightly for 7 nights (cardiac trial); personal inhaler 3 times a day for a week (blend).

Who was studied

Hospitalised cardiac patients; adults with self-rated burnout; drivers in a test.

Limits

Small samples, subjective outcomes, no long-term follow-up, mixed oils.

Why researchers looked

People smell peppermint to feel awake and refreshed.

Traditional use

Used as a refreshing aroma (general background, not verified in this file).

Proposed mechanism Pharmacological theory

Not tested in these studies. The stimulating effect may come from the strong cool smell, from expectation or from nerve effects of menthol.

A proposed mechanism does not show that the effect happens in people.

Inhaled use was well tolerated in these abstracts; smelling strong oils can trigger headache or asthma in some people.

^{83 140 60 106 65}

Anxiety and stress (aroma before procedures)

Very low certainty

Smelling peppermint oil lowered anxiety scores in hospital patients in a few small trials, but peppermint was weaker than lavender in children, and when mixed with lavender it added nothing over lavender alone. The evidence is thin.

5 studies0.2 mL on an eye pad for 20 minutes; nebulised aroma for children; pa…

Studies, doses and limits

What the trials found

Sharafi 2026: patients with acute coronary syndrome had 0.2 mL peppermint oil on an eye pad for 20 minutes versus saline; anxiety fell from 24.64 to 19.55 and stress from 25.00 to 17.18 (P<0.001), and heart rate and blood pressure fell. Abdel Rehim 2025: in 100 children having dental treatment, anxiety fell by 0.68 points with peppermint versus 1.80 with lavender and 2.04 with chamomile, with the control group rising 0.04. Hancı 2025: in 135 women before breast biopsy, lavender and lavender-peppermint both reduced anxiety and pain versus no aroma, with no difference between them. Liu 2025 (below) also showed less anxiety after surgery. Kingsley 2023 found no extra anxiety benefit in teenagers except a small p=0.03 anxiety difference.

Results

Small short-term drops in rated anxiety in hospital patients; peppermint was less effective than lavender or chamomile where compared.

Effect sizes as reported

ACS trial: P<0.001 on anxiety and stress scales; children: peppermint -0.68 vs lavender -1.80 vs chamomile -2.04; other trials give p-values only.

Why this rating

Short trials from a few countries, mostly unblinded in practice because the smell is obvious; self-rated scales; peppermint often mixed with other oils or compared to better ones.

Form and dose studied

0.2 mL on an eye pad for 20 minutes; nebulised aroma for children; pads with blend on the shoulder 20 minutes before a procedure.

Who was studied

Patients before or during procedures or hospital stays; children having dental work.

Limits

Single sessions; no trial of long-term anxiety disorders; the size of the blood-pressure drop in the ACS trial looks very large and needs replication.

Why researchers looked

Waiting for a hospital procedure is stressful, and aroma is a cheap, low-risk add-on.

Traditional use

Not a main traditional use of peppermint (general background, not verified in this file).

Proposed mechanism Pharmacological theory

Not tested directly. Pleasant smells and attention to a calming ritual probably play a role.

A proposed mechanism does not show that the effect happens in people.

Used by inhalation only; asthma and migraine can be triggered by strong smells.

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Confusion (delirium) after hip or knee surgery in older adults

Very low certainty

In one 2025 trial of 178 older adults, smelling peppermint oil after joint replacement surgery was linked to less delirium in the first three days. It is a single, borderline result that needs repeating.

1 studiesInhaled peppermint essential oil (dose not given in the abstract) in …

Studies, doses and limits

What the trials found

Liu 2025: 178 older patients (median age 70) having hip or knee replacement were randomised to inhale peppermint oil or normal saline; delirium within 3 days was 7.9% versus 19.1% (risk ratio 0.412; 95% CI 0.179 to 0.944; P=0.048). Pain at rest and in activity over 3 days and anxiety over 2 days were lower with peppermint (all P<0.05).

Results

Less delirium with inhaled peppermint (7.9% vs 19.1%) in one trial; borderline statistically.

Effect sizes as reported

RR 0.412 (95% CI 0.179 to 0.944); risk difference -0.112 (95% CI -0.215 to -0.014).

Why this rating

One trial, one hospital, P=0.048, and the dose and delirium assessment tool are not in the abstract; blinding to a smell is imperfect.

Form and dose studied

Inhaled peppermint essential oil (dose not given in the abstract) in the first postoperative days.

Who was studied

Older adults after major joint replacement.

Limits

Single trial; no replication; no long-term cognitive follow-up; limited to a specific surgery.

Why researchers looked

Delirium after surgery is common in older people and linked to worse outcomes, and drug-free prevention is wanted.

Proposed mechanism Preliminary mechanism

The authors point to cognitive-enhancing and neuroprotective properties of peppermint oil, which come from lab work and are unproven for this use.

A proposed mechanism does not show that the effect happens in people.

No harms reported in the abstract; check hospital rules before bringing oils into a ward.

⁷⁹

Exercise effort and performance (oil, aroma, menthol rinse)

Mixed findings

Results are mixed. Two small studies by one author and one Brazilian trial reported longer time to exhaustion or stronger performance after swallowing the oil, while three other studies found no effect. Peppermint did not make running feel easier in the runner trial, and menthol mouth rinses and gels did not clearly improve performance.

9 studies0.05 mL oil in 500 mL water (one to two studies); 50 microlitres sing…

Studies, doses and limits

What the trials found

Meamarbashi 2013: 12 men swallowed 0.05 mL oil in water daily for 10 days; time to exhaustion rose from 664.5 to 830.2 s (p<0.001), apparently without a control group. Meamarbashi 2014: in 30 students a single 50 microlitre dose improved grip force (+36.1%), jumps (+7.0%) and reaction time versus control. Miranda Neto 2023: 14 recreational runners ran 109.9 vs 98.5 minutes to exhaustion with oil versus placebo (p=0.009), yet perceived effort, temperature and thermal comfort did not differ. Shepherd 2017 (7 people, 10 days): no change in peak oxygen use or time to exhaustion. Pournemati 2009 (36 women soccer players): inhaled peppermint had no effect. Rites 2024 (11 soccer players): inhaling the oil did not clearly help jumping. Menthol gel (Vogel 2023, 14 runners in heat) did not change distance or perceived exertion, and two 2026 mouth-rinse reviews found menthol not clearly better than placebo.

Results

Some small positive studies, an equal number of null ones; no clear change in how hard exercise feels.

Effect sizes as reported

Time to exhaustion +11.4 minutes in the runner trial (effect size 0.826); mouth rinse network meta-analysis: menthol not significantly different from placebo.

Why this rating

Tiny studies, different doses and ways of use, and the largest gains come from the author with the least rigorous designs; null results in others. Not a formal GRADE rating.

Form and dose studied

0.05 mL oil in 500 mL water (one to two studies); 50 microlitres single dose; inhaled; menthol gel 0.5%; menthol mouth rinse.

Who was studied

Healthy young men and recreational or trained athletes; few women.

Limits

Overlaps with the body file (muscle and breathing); here only effort and performance are covered. Swallowing essential oil is not advised without product guidance.

Why researchers looked

Athletes look for cool, refreshing, easy-to-use aids; menthol is known as a cooling sensation.

Proposed mechanism Pharmacological theory

Menthol activates cold receptors and could change how hot or hard exercise feels. Proposed effects on bronchial muscle relaxation and lactate are the authors' ideas and were not measured.

A proposed mechanism does not show that the effect happens in people.

Swallowing the oil can cause heartburn and stomach upset; do not exceed product directions.

^{91 92 113 97 125 117 142 77 131}

Irritable bowel syndrome (enteric-coated oil)

Mixed findings

Peppermint oil in coated capsules has been tested for irritable bowel syndrome (IBS) in many trials. Older and pooled results say it helps belly pain and overall symptoms. Three newer, larger trials did not meet their main targets, and reviewers rate the overall evidence very low. Side effects such as heartburn are more common than with placebo.

8 studiesEnteric-coated or ileocolonic-release capsules of 180-182 mg, two or …

Studies, doses and limits

What the trials found

Pooled reviews: a 2022 review of 10 trials (1,030 patients) found peppermint oil better than placebo for global symptoms (risk of not improving 0.65; 95% CI 0.43-0.98; NNT 4) and abdominal pain (0.76; 0.62-0.93; NNT 7), with more adverse events (RR 1.57) and very low quality evidence. A 2019 review of 12 trials (835 patients) found global improvement RR 2.39 (1.93-2.97) and pain RR 1.78 (1.43-2.20), NNT 3 and 4; adverse events did not differ significantly (9.3% vs 6.1%). A 2014 review of 9 trials (726 patients) found RR 2.23 and 2.14. A 2020 network review of 51 trials (13 at low risk of bias) ranked peppermint oil first for global symptoms (RR 0.63; 0.48-0.83) and tricyclic antidepressants first for pain, with no significant differences between active treatments. Individual trials: a 2007 trial of 57 patients found 75% vs 38% responders at 4 weeks; a 2013 trial in 74 diarrhoea-type IBS patients found pain lower at 6 weeks (4.94 vs 6.15) but back up two weeks after stopping, with no change in other symptoms or quality of life. Newer trials: in 189 patients (2020), 182 mg capsules for 8 weeks did not significantly beat placebo on the official pain-response and overall-relief targets (46.8% and 41.3% vs 34.4% pain response), although small-intestinal-release capsules did better on secondary pain, discomfort and severity scores (P about .016-.020). In a 6-week US trial (2021) of 180 mg three times daily, the IBS severity score fell by 90.8 with peppermint oil and 100.3 with placebo (P=0.97).

Results

Mixed. Older small trials and the pooled reviews favour peppermint oil, while the two largest recent trials missed their main targets because the placebo group also improved a lot.

Effect sizes as reported

Global symptoms RR 0.65 (0.43-0.98) in the 2022 review; RR 2.39 (1.93-2.97) in the 2019 review (the two reviews code the outcome in opposite directions). Newer trials: pain response 46.8% vs 34.4% (P=.170); severity score change -90.8 vs -100.3 (P=0.97).

Why this rating

Pooled reviews lean positive but include small, older trials and are rated very low quality by their own authors. The newer, larger trials with modern endpoints were mostly null on their main outcome. The rating is the compiler's.

Form and dose studied

Enteric-coated or ileocolonic-release capsules of 180-182 mg, two or three times daily, for 4 to 12 weeks. Plain (uncoated) oil was not the form tested in these trials.

Who was studied

Adults with IBS; mostly women; short trials (2-12 weeks).

Limits

Placebo response in IBS trials is high. Most trials are short and use different products, doses and endpoints. Long-term benefit is unknown. A 2007 trial found pain returned after stopping.

Why researchers looked

IBS causes cramping pain, bloating and bowel changes, and treatment options are limited. Peppermint oil relaxes gut muscle in lab and human gut studies, so it has been a natural candidate.

Traditional use

Peppermint tea and oil are long used in many food traditions as a digestive aid. This indication is a modern clinical question as much as a traditional one.

Proposed mechanism Pharmacological theory

The authors of one trial describe the active part, menthol, as a calcium channel blocker in gut muscle, which would relax it. That is a proposed explanation, not something these trials measured.

A proposed mechanism does not show that the effect happens in people.

Adverse events were more common with peppermint oil in the 2022 review and the 2020 trial; they were mild. Heartburn was the most commonly reported event in the 2014 review. See the safety file for full cautions.

^{58 8 67 16 148 103 18 7}

Belly pain in children (IBS and functional abdominal pain)

Mixed findings

A 2026 trial of 228 children found peppermint oil and peppermint sweets worked no better than placebo for stomach pain. A small 2001 trial and a 2017 review had suggested a benefit. The best current evidence is that it does not help beyond placebo in this age group.

3 studiesCapsules of 182 mg twice daily (ages 8-11) or three times daily (12-1…

Studies, doses and limits

What the trials found

2026 Dutch trial (13 hospitals, 228 children aged 8-18): treatment success (30% or more drop in pain) was 44.0% with peppermint oil capsules (182 mg), 37.3% with placebo, 38.7% with peppermint sweets (OR 1.33; 97.5% CI 0.58-3.09). Adequate relief was 53.3%, 49.3% and 44.9%. Adverse events were mild and infrequent. A 2001 trial of 42 children with IBS reported that 75% on enteric-coated capsules had less severe pain after 2 weeks (the abstract gives no placebo figure). A 2017 review of 14 paediatric herbal trials found evidence for peppermint oil in functional abdominal pain; it pre-dates the 2026 trial.

Results

No benefit over placebo in the largest and newest trial.

Effect sizes as reported

Peppermint oil vs placebo, treatment success: OR 1.33 (97.5% CI 0.58-3.09); adequate relief OR 1.15 (0.54-2.47).

Why this rating

One large recent null trial against one small older positive trial and a review that relied on small trials. The rating is the compiler's.

Form and dose studied

Capsules of 182 mg twice daily (ages 8-11) or three times daily (12-18); sweets with 9.2 mg; 8 weeks.

Who was studied

Children and teenagers aged 8-18.

Limits

The 2001 trial is very small and its abstract lacks the placebo result. No peppermint oil trial in children under 8 was found.

Why researchers looked

Recurrent belly pain is common in children, and drugs are few. Parents and doctors ask about herbal options like peppermint oil.

Traditional use

Peppermint tea and oil are long used in many food traditions as a digestive aid. This indication is a modern clinical question as much as a traditional one.

Proposed mechanism Pharmacological theory

Same theory as in adults: a relaxing effect on gut muscle. Not measured in these abstracts.

A proposed mechanism does not show that the effect happens in people.

Adverse events mild and infrequent in the 2026 trial. See the safety file for cautions in children.

^{141 71 11}

Functional dyspepsia (upper belly pain and fullness)

Low certainty

A fixed mix of peppermint oil and caraway oil has been tested in several trials for indigestion with no clear cause. Pooled results favour the mix over placebo and match one standard drug. The studies are small and the mix means peppermint oil alone is not tested.

4 studiesFixed enteric-coated capsule with peppermint oil 90 mg plus caraway o…

Studies, doses and limits

What the trials found

A 2019 review of 5 placebo-controlled trials (578 people) found the peppermint-caraway mix improved global symptoms (RR for not much improvement 0.59; 95% CI 0.49-0.71; NNT 3) and epigastric pain (RR 1.61; 1.28-2.03; NNT 3), with no significant difference in total adverse events; the authors rate evidence low or very low. A 2017 trial of 114 outpatients (Menthacarin, one capsule twice daily, 4 weeks) found pain falling by 7.6 points vs 3.4 with placebo and discomfort by 3.6 vs 1.3. A 1999 trial of 120 patients compared the mix (peppermint oil 90 mg plus caraway oil 50 mg, one capsule twice daily) with cisapride and found equivalent pain reduction (4.62 vs 4.60 points). A 1996 trial of 45 patients (39 analysed) found pain and global impression better than placebo (p=0.015, 0.008); 63.2% of the mix group were pain-free.

Results

Better than placebo and similar to cisapride in four-week trials of a peppermint-caraway mix.

Effect sizes as reported

Global improvement RR 0.59 (0.49-0.71); epigastric pain RR 1.61 (1.28-2.03); NNT 3 for both.

Why this rating

Consistent direction but small, short trials of a combination product; authors rate low or very low. The rating is the compiler's.

Form and dose studied

Fixed enteric-coated capsule with peppermint oil 90 mg plus caraway oil 50 mg, one twice daily, for 4 weeks (other proprietary mixes in some trials).

Who was studied

Adults with functional dyspepsia.

Limits

Results apply to the combination product, not to peppermint oil alone, peppermint tea or plain capsules. Short trials; long-term effect unknown.

Why researchers looked

Functional dyspepsia causes upper-belly pain, fullness and early satiety with no visible disease, and few treatments work for many people.

Traditional use

Peppermint and caraway are both long-used European kitchen and tea herbs for indigestion and gas.

Proposed mechanism Pharmacological theory

The authors of one trial describe the active part, menthol, as a calcium channel blocker in gut muscle, which would relax it. That is a proposed explanation, not something these trials measured.

A proposed mechanism does not show that the effect happens in people.

No significant increase in total adverse events in the 2019 review (NNH 40). Heartburn is a known concern with peppermint oil in other conditions; see the safety file.

^{76 116 81 86}

Oesophageal spasm: chest pain and trouble swallowing

Very low certainty

A very small test and a chart review suggest peppermint oil may relax spasm in the food pipe and ease chest pain or swallowing trouble in some people. This is early work with no placebo group.

2 studiesFive drops in 10 mL water as a single dose (test); two dissolvable pe…

Studies, doses and limits

What the trials found

In 8 patients with diffuse oesophageal spasm, a drink of 5 drops in 10 mL water removed simultaneous contractions in every patient (p<0.01) 10 minutes later, and 2 of 8 had chest pain that went away. In a chart review of 38 patients given peppermint tablets, 24 (63%) reported improvement (12 much better, 12 slightly better), 14 no change, none worse; best response in distal oesophageal spasm (83%) and outflow obstruction (100%).

Results

Pressure patterns improved briefly; symptoms improved in about two in three people in a chart review.

Effect sizes as reported

Simultaneous contractions eliminated in 8 of 8 (p<0.01); symptom improvement 24 of 38 (63%).

Why this rating

Two tiny uncontrolled studies with no placebo and subjective outcomes. The rating is the compiler's.

Form and dose studied

Five drops in 10 mL water as a single dose (test); two dissolvable peppermint tablets before meals (chart review).

Who was studied

Adults with oesophageal motility disorders.

Limits

No control group in either study; single dose or retrospective; patient-reported outcomes. Chest pain must be checked by a doctor first.

Why researchers looked

Spasm of the food pipe can cause chest pain and swallowing trouble that mimic heart problems, and treatment is often unsatisfying.

Traditional use

No traditional use for this specific condition is established.

Proposed mechanism Preliminary mechanism

The authors reasoned that peppermint oil, as a smooth muscle relaxant, could calm oesophageal contractions. Measured only as a 10-minute pressure change in 8 patients.

A proposed mechanism does not show that the effect happens in people.

These two studies did not report side effects in detail. Heartburn was the most commonly reported side effect in IBS reviews; see the safety file.

^{111 66}

Colon spasm during colonoscopy

Mixed findings

Studies are split. Peppermint oil put into the colon through the scope tends to reduce spasm. Capsules taken by mouth beforehand were helpful in one trial and not in two others. A pooled review found less spasm but said results varied a lot.

5 studies50 mL of peppermint oil solution injected through the scope; or enter…

Studies, doses and limits

What the trials found

A 2020 review of 6 studies found lower spasm (risk difference -0.39; P=0.02), severe spasm (-0.15; P=0.04) and peristalsis (-0.27; P<=0.001), and higher adenoma detection (RR 1.31; P=0.01, only two studies), with significant heterogeneity. A 2019 US trial (48 patients, 50 mL injected through the scope) found complete absence of spasm in 58.3% vs 45.8% (P=0.05) and faster time to the caecum (7.2 vs 10.3 min; P=0.04); adenoma detection 45.8% vs 37.5% was not significant (P=0.56). A 2012 trial (65 patients, Colpermin capsules 4 hours before) found shorter procedures and less spasm and pain. A 2017 trial (80 patients, the same product) found no effect on caecal time, tolerance or sedation use. A 2021 trial of sustained-release capsules (IBgard) before colonoscopy found no difference in spasm scores or adenoma detection (47.8% vs 43.1%; p=0.51).

Results

Helpful in trials where oil goes straight into the colon; oral capsules gave mixed results.

Effect sizes as reported

Pooled: spasm risk difference -0.39 (P=0.02). Direct injection: spasm-free 58.3% vs 45.8% (P=0.05). Oral IBgard: no difference.

Why this rating

Positive pooled and injection results but heterogeneity, small trials and two null oral-capsule trials. The rating is the compiler's.

Form and dose studied

50 mL of peppermint oil solution injected through the scope; or enteric-coated capsules 4 hours beforehand (dose not stated in the abstracts).

Who was studied

Adults having screening, surveillance or diagnostic colonoscopy.

Limits

Different doses, routes and timing across trials; adenoma detection tested in only a few; this is a procedure given by a doctor, not a home use.

Why researchers looked

Colon muscle spasm makes it harder to move the scope and see the bowel wall. Doctors look for safe alternatives to injected antispasmodics.

Traditional use

Not a traditional use; a modern procedural use.

Proposed mechanism Pharmacological theory

The authors of one trial describe the active part, menthol, as a calcium channel blocker in gut muscle, which would relax it. That is a proposed explanation, not something these trials measured.

A proposed mechanism does not show that the effect happens in people.

No harms were reported in the abstracts; tolerance was similar to placebo.

^{13 121 124 6 45}

Gut spasm during upper endoscopy, ERCP and barium X-rays

Low certainty

In several studies, peppermint oil put into the stomach or bowel through the scope or mixed with barium reduced muscle spasm, similar to injected antispasmodics, with fewer side effects. These are procedures done by doctors, not home uses.

6 studiesPeppermint oil solutions put into the gut by the doctor (for example …

Studies, doses and limits

What the trials found

Upper endoscopy: a 100-patient trial found peppermint oil put in the stomach opened the pylorus more than injected hyoscine and settled the antral contraction ring faster (97.1 vs 185.9 s; p<0.0001), with no significant side effects, while hyoscine caused dry mouth, blurred vision and urinary retention. A large observational study of 8,269 procedures found a similar overall antispasmodic score to hyoscine (4.025 vs 4.063); in patients under 70 peppermint scored slightly lower (3.923 vs 4.062; P<0.001), while in those 70 and over it was similar (4.073 vs 4.064). ERCP: in 40 patients, peppermint alone was enough in 91.4% (37 of 39); duodenal movement was none or mild in 69.2%, with no serious complications. Barium X-rays: in 383 patients, spasm-free barium enema films were 13.4% with no treatment, 38.1% with Buscopan, 41.8% (peppermint in the tube) and 37.8% (peppermint in the barium). In 141 patients, spasm was absent in 60% vs 35% with plain barium (p<0.001). For barium meals, spasm scores were lower in the oesophagus, lower stomach and duodenal bulb (P<0.001) in 205 vs 215 matched controls.

Results

Spasm was reduced in these procedures, about as well as injected drugs.

Effect sizes as reported

Barium enema: spasm-free 41.8% / 37.8% (peppermint) vs 13.4% (none) (p<0.0005). Endoscopy: 97.1 s vs 185.9 s to settle (p<0.0001).

Why this rating

Several controlled trials agree in direction, but they are older, small to moderate, and not all randomised; ERCP data are uncontrolled. The rating is the compiler's.

Form and dose studied

Peppermint oil solutions put into the gut by the doctor (for example 20 mL of 1.6% or 3.2% for ERCP; 30 mL mixed into barium).

Who was studied

Adults having endoscopy, ERCP or barium X-ray examinations.

Limits

Done only in procedures by clinicians; doses and solutions vary; less effective than hyoscine in younger people in one study.

Why researchers looked

Antispasmodic injections such as hyoscine can cause dry mouth, blurred vision and urinary retention, so a local, safer alternative is attractive.

Traditional use

Not a traditional use; a modern procedural use.

Proposed mechanism Pharmacological theory

The authors of one trial describe the active part, menthol, as a calcium channel blocker in gut muscle, which would relax it. That is a proposed explanation, not something these trials measured.

A proposed mechanism does not show that the effect happens in people.

No significant side effects were reported with peppermint oil in these abstracts.

^{52 57 149 12 98 129}

Nausea after surgery (smelling peppermint oil)

Low certainty

Inhaling peppermint oil has been tested for nausea after operations. Results are mixed: some small studies find less nausea, while a saline-placebo trial found the same relief from breathing alone. A 2024 review of aroma treatments gave the overall evidence a low rating.

8 studiesInhaled peppermint oil (about 2% solution or a few drops on gauze) or…

Studies, doses and limits

What the trials found

A 2024 review of 8 trials found aromatherapy lowered postoperative nausea severity (SMD -0.93; 95% CI -1.64 to -0.22) but not vomiting, with low-certainty evidence; ginger, lavender and peppermint were highlighted. A 2026 trial of 106 women having laparoscopic gynaecologic surgery found nausea and vomiting within 24 hours in 52.8% with inhaled 2% peppermint oil vs 73.6% with saline (P=0.043). A 2025 trial of 80 rhinoplasty patients given 20 drops of 2% peppermint essence by mouth before surgery found less nausea (P<0.001) but no difference in vomiting or pain. A 2025 trial of 182 patients found a blend of peppermint, ginger and lavender lowered nausea severity (p<0.001), with antiemetic use 30.77% vs 52.38% (not significant). A 2020 study found no significant difference (P=.28). A 2004 trial of 33 patients found nausea fell in all groups equally, including saline and alcohol sniffing. A 2012 trial in 35 women after Caesarean section found lower nausea with peppermint spirits than with placebo or standard antiemetics at 2 and 5 minutes. A 1997 trial of gynaecological patients found less nausea than placebo on the day of surgery (P=0.02).

Results

Some reductions in nausea; vomiting less clear; one control trial suggests breathing alone helps.

Effect sizes as reported

Review: nausea SMD -0.93 (-1.64 to -0.22). 2026 trial: PONV 52.8% vs 73.6%.

Why this rating

Review authors rated low certainty (GRADE); trials are small and inconsistent; mixed oils in several. The rating is the compiler's.

Form and dose studied

Inhaled peppermint oil (about 2% solution or a few drops on gauze) or 20 drops of 2% essence by mouth in one trial.

Who was studied

Adults after surgery, mostly gynaecological.

Limits

Blinding is hard with a smell; blends make peppermint alone hard to judge; one trial used oral drops, which is not a standard use.

Why researchers looked

Nausea and vomiting after surgery are common and distressing. Aromas are cheap and low risk compared with drugs.

Traditional use

Peppermint has long been sniffed or sipped for queasiness.

Proposed mechanism Preliminary mechanism

The reason is not known. One trial suggests the benefit may come from slow deep breathing while sniffing, not from the aroma.

A proposed mechanism does not show that the effect happens in people.

No adverse events reported in the 2025 blend trial. Swallowing essential oil needs caution; see the safety file.

^{144 134 108 59 63 10 75 135}

Nausea from chemotherapy (inhaled or dabbed on)

Low certainty

A few small trials suggest peppermint aroma can lower chemotherapy-related nausea when used with usual anti-nausea drugs. Reviews are cautious: there are few trials and many different oils and methods.

4 studiesOne drop between nose and upper lip three times daily for 5 days afte…

Studies, doses and limits

What the trials found

A 2024 review of 25 comparisons in cancer patients found aromatherapy reduced nausea (SMD -0.85; 95% CI -1.23 to -0.46) but not vomiting alone (SMD -0.24; -1.03 to 0.55); inhalation and massage worked, and peppermint oil was reported as particularly successful in chemotherapy-induced cases. A 2021 systematic review of 11 inhaled aroma studies found 7 of 9 adult studies significant, with peppermint or ginger relieving both nausea and vomiting in 4 of 7; diffusing oil into the room and the two paediatric studies showed no benefit. A 2021 quasi-randomised study dabbed one drop of peppermint oil under the nose three times daily for 5 days alongside usual drugs; nausea scores fell in most regimens (for example mean difference 4.00 with Folfirinox, P<0.001) but not with cisplatin (P=0.642). A 2023 trial of 90 children aged 2-12 with leukaemia found lower nausea scores with a peppermint and lemon diffuser than with water or nothing.

Results

Less nausea in several small studies, not with the strongest anti-cancer drug (cisplatin) in one study.

Effect sizes as reported

Review: nausea SMD -0.85 (-1.23 to -0.46). Quasi-randomised study: nausea VAS difference 4.00 (Folfirinox), 0.56 (cisplatin, P=0.642).

Why this rating

Small, mixed-method studies; one open-label and quasi-randomised; blends in some. The rating is the compiler's.

Form and dose studied

One drop between nose and upper lip three times daily for 5 days after chemotherapy; inhalation of peppermint oil; diffusers in children.

Who was studied

Adults and children with cancer having chemotherapy.

Limits

Usually added to standard drugs; effect on vomiting unclear; chemotherapy patients should check any essential oil with their care team.

Why researchers looked

Nausea remains a major side effect despite anti-nausea drugs, affecting quality of life.

Traditional use

Peppermint has long been used for queasiness; its use in cancer care is recent.

Proposed mechanism Preliminary mechanism

Not established; the same breathing and aroma theory as for surgery nausea.

A proposed mechanism does not show that the effect happens in people.

No harms are reported in the abstracts. People having chemotherapy should ask their cancer team before using essential oils.

^{3 139 25 157}

Nausea and vomiting in pregnancy

Mixed findings

Three small trials gave different answers. Peppermint alone matched placebo twice; a lemon and peppermint blend helped from day 2 in one trial. Overall the evidence is weak and mixed.

3 studiesInhaled peppermint oil or a lemon-peppermint blend, 3-4 drops on a co…

Studies, doses and limits

What the trials found

In 56 pregnant women (2018), inhaled peppermint oil for 4 days lowered nausea scores in both groups (p<0.001) with no difference between peppermint and placebo. In 60 women (2012), peppermint oil near the bed for four nights did not change nausea or vomiting significantly. In 90 women (2020), a lemon and peppermint inhaler for 4 days gave lower nausea and vomiting scores from day 2 than placebo (time effect F=22.92, p<0.001 in the aroma group only).

Results

Peppermint alone did not beat placebo; a lemon-peppermint blend did in one trial.

Effect sizes as reported

No effect sizes with confidence intervals are given in the abstracts.

Why this rating

Three small, short trials with conflicting results; the positive one used two oils. The rating is the compiler's.

Form and dose studied

Inhaled peppermint oil or a lemon-peppermint blend, 3-4 drops on a cotton ball, 4 days.

Who was studied

Pregnant women with mild to moderate nausea, 6-20 weeks (first-half pregnancy).

Limits

Short follow-up; mild cases only; blends confuse the question. Safety in pregnancy was not studied.

Why researchers looked

Many pregnant women want a drug-free option for morning sickness.

Traditional use

Mint teas are widely used at home for queasiness in pregnancy.

Proposed mechanism Preliminary mechanism

Unknown. The authors of one trial suggest aroma effects may be partly psychological.

A proposed mechanism does not show that the effect happens in people.

These trials did not study safety in pregnancy; ask a doctor or midwife before using essential oils while pregnant. See the safety file.

^{61 118 109}

Bowel recovery after Caesarean section (mint drops)

Not enough evidence

One trial of 102 women found mint drops brought back bowel sounds and gas sooner after a Caesarean section. It is a single study, and its abstract does not name peppermint.

1 studiesMint drops (dose not stated in the abstract).

Studies, doses and limits

What the trials found

In 102 women (51 per group), time to first bowel sound was 5.78 hours with mint drops vs 9.05 hours with placebo, and time to first gas 7.87 vs 12.24 hours. No woman had nausea or vomiting.

Results

Faster return of bowel sounds and gas.

Effect sizes as reported

First bowel sound 5.78 vs 9.05 hours; first gas 7.87 vs 12.24 hours.

Why this rating

One small trial; the abstract says mint, not peppermint; no other trial found. The rating is the compiler's.

Form and dose studied

Mint drops (dose not stated in the abstract).

Who was studied

Women after Caesarean section.

Limits

Single trial, species not confirmed, no long-term data.

Why researchers looked

A slow-moving bowel after surgery (ileus) delays eating and going home.

Traditional use

Mint is a traditional gut-soothing herb; no specific traditional use for ileus.

Proposed mechanism Pharmacological theory

Unknown; presumed gut muscle effect is not tested.

A proposed mechanism does not show that the effect happens in people.

No harms are reported in the abstract.

¹⁰¹

Period pain (primary dysmenorrhoea)

Low certainty

A small crossover trial found peppermint capsules lowered period pain and its length, like mefenamic acid, though bleeding fell less. A 2025 review of five trials (499 women) also found less pain, with calls for better studies.

2 studiesPeppermint extract capsules for 3 days starting from the first day of…

Studies, doses and limits

What the trials found

In a 2016 crossover trial of 127 students, pain intensity and duration were significantly lower after peppermint capsules and after mefenamic acid (P<0.05). Bleeding was lower with mefenamic acid than with peppermint. Nausea and diarrhoea were lower with peppermint, but extra painkiller use was higher in the peppermint group (P<0.05). A 2025 systematic review of 5 randomised trials (499 participants; dysmenorrhoea and premenstrual symptoms) rated three as high quality and two as low, and reported statistically significant reductions in pain severity, improved cognitive function and fewer gastrointestinal symptoms.

Results

Less period pain; peppermint did not reduce bleeding.

Effect sizes as reported

No effect sizes or confidence intervals are given in the abstracts; only P<0.05.

Why this rating

Small trials with self-reported pain, one crossover; the review rates quality as mixed. The rating is the compiler's.

Form and dose studied

Peppermint extract capsules for 3 days starting from the first day of the period (dose not stated in the abstract).

Who was studied

Young women with primary dysmenorrhoea, Hamadan; review covers premenstrual symptoms too.

Limits

Self-reported scores; extra painkiller use was higher with peppermint; long-term use not studied.

Why researchers looked

Period pain affects many young women, and painkillers cause stomach upset for some. Peppermint is a traditional remedy for cramps.

Traditional use

Mint preparations are a folk remedy for cramps; no historical source was checked for this profile.

Proposed mechanism Pharmacological theory

The trial authors point to menthol's pain-modulating effect via temporary-receptor proteins, a proposed mechanism not tested in the trial.

A proposed mechanism does not show that the effect happens in people.

Nausea and diarrhoea were lower than with mefenamic acid. Heavy or unusual period pain should be checked by a doctor.

^{85 74}

Sore, cracked nipples while breastfeeding (applied to skin)

Low certainty

Several trials from the same region found peppermint water or gel on the nipples prevented cracks and eased pain, better than lanolin or breast milk in two, though one trial found it no different from lanolin or dexpanthenol cream.

5 studiesPeppermint water, gel or cream on nipples after feeds; menthol essenc…

Studies, doses and limits

What the trials found

A 2007 trial of 216 first-time mothers found fewer cracks with peppermint gel than with lanolin or placebo gel after 14 days (chi-square 16.8, P=0.01). A second 2007 trial of 196 mothers found cracks in 9% with peppermint water vs 27% with expressed breast milk (P<0.01) and lower pain (OR 5.6; 95% CI 2.2-14.6). A 2014 trial of 110 mothers with fissures found pain and fissure severity fell significantly with menthol essence (four drops after each feed) compared with their own milk. A 2015 trial of 126 mothers found peppermint, lanolin and dexpanthenol creams gave similar results. A 2024 review of 11 studies (1,495 mothers) found peppermint reduced nipple trauma.

Results

Fewer cracks than lanolin or milk in two trials; no difference from lanolin in a third.

Effect sizes as reported

Cracks 9% vs 27% (P<0.01); pain OR 5.6 (2.2-14.6).

Why this rating

Several randomised trials, but from similar settings and often with milk rather than placebo as comparator. The rating is the compiler's.

Form and dose studied

Peppermint water, gel or cream on nipples after feeds; menthol essence 4 drops after each feed, for up to 14 days.

Who was studied

First-time breastfeeding mothers.

Limits

Comparators vary; some not blinded; infant exposure to the product was not examined in the abstracts.

Why researchers looked

Nipple pain and cracks are a leading reason mothers stop breastfeeding early.

Traditional use

Peppermint water is a popular folk remedy for nipple cracks in northwest Iran.

Proposed mechanism Pharmacological theory

The authors describe peppermint as an anti-inflammatory and anti-infection herb; this was not tested in the trials.

A proposed mechanism does not show that the effect happens in people.

The abstracts do not report infant exposure or safety; see the safety file before using any menthol product on the breast.

^{93 120 4 122 126}

Itch (applied to skin)

Very low certainty

Two small trials found peppermint oil on the skin eased itch in people with liver, kidney or diabetes-related itch and in pregnant women, compared with petrolatum or a placebo oil.

2 studiesTopical peppermint oil, 0.5% in sesame oil in one trial, twice daily …

Studies, doses and limits

What the trials found

In 50 adults with chronic itch from liver, kidney or diabetes, peppermint oil twice daily for 2 weeks improved all 5-D itch scale measures versus petrolatum (total score P<0.05). In 96 pregnant women with itch, 0.5% peppermint oil in sesame oil twice daily for 2 weeks gave lower itch severity than placebo (p=0.003).

Results

Less itch than the comparison in both trials.

Effect sizes as reported

No effect sizes with confidence intervals in the abstracts; P<0.05 and p=0.003.

Why this rating

Two small, short trials with only P values. The rating is the compiler's.

Form and dose studied

Topical peppermint oil, 0.5% in sesame oil in one trial, twice daily for 2 weeks.

Who was studied

Adults with chronic itch; pregnant women with itch.

Limits

Small, 2 weeks, one comparison per condition; not tested for itch from other causes.

Why researchers looked

Chronic itch is hard to treat, and people who are pregnant or have organ disease often avoid drugs.

Traditional use

The authors of one trial describe peppermint as a traditional drug in Iran.

Proposed mechanism Pharmacological theory

The authors of one trial say peppermint lowers skin temperature; this was not measured in the trial.

A proposed mechanism does not show that the effect happens in people.

Undiluted peppermint oil can irritate skin; see the safety file.

^{26 5}

Connections to the rest of health

How Peppermint connects to the rest of our health knowledge graph. Every link says what kind of connection it is. A safety link (for example to the liver) is a warning, not a benefit. A study that merely mentions a topic never creates a benefit link.

Explore every connection: goals, body systems, organs, symptoms, genes

Kind of connection Connected to Search

A. Wellness goals

Connected to	Kind of connection	Evidence status	Context	Studies
Calm Relaxation	Potential benefit	Low certainty	Tension-type headache (oil on the forehead and temples): A 10% peppermint oil in alcohol, rubbed on the forehead and temples, eased tension headache about as well as 1,000 mg of paracetamol in one small controlled trial from 1996. It is the best-supported mind-related use of peppermint, but the evidence is thin, old and mostly from one research group. Migraine attacks (nose drops or menthol gel): Menthol or peppermint oil on the skin or in the nose has been tried for the pain of a migraine attack. One randomised trial found nose drops of 1.5% peppermint oil helped about as well as lidocaine drops, and a small open pilot of menthol gel saw some relief. The evidence is weak, and rat work shows menthol can also stimulate pain pathways.	^{43 42 44 114 130 80 128 69 123 2 46 79}
Stress Reduction	Potential benefit	Not enough evidence	Chronic headache in teenagers (aroma during a foot bath): In a trial of teenagers with long-term headaches, adding peppermint oil to a relaxing foot bath did not reduce pain or anxiety more than the foot bath alone. The relaxation itself helped. Anxiety and stress (aroma before procedures): Smelling peppermint oil lowered anxiety scores in hospital patients in a few small trials, but peppermint was weaker than lavender in children, and when mixed with lavender it added nothing over lavender alone. The evidence is thin.	^{69 123 2 46 79}
Mental Clarity	Potential benefit	Mixed findings	Alertness, memory and focus (smelling or swallowing the oil): Studies on whether peppermint sharpens the mind are mixed. Two controlled studies found better memory or attention and less mental fatigue, one found no effect on vigilance, and a 2025 review of the smell studies says no firm conclusion can be drawn yet.	^{100 65 51 106 132 104}
Better Focus	Potential benefit	Mixed findings	Alertness, memory and focus (smelling or swallowing the oil): Studies on whether peppermint sharpens the mind are mixed. Two controlled studies found better memory or attention and less mental fatigue, one found no effect on vigilance, and a 2025 review of the smell studies says no firm conclusion can be drawn yet.	^{100 65 51 106 132 104}
Memory Support	Potential benefit	Mixed findings	Alertness, memory and focus (smelling or swallowing the oil): Studies on whether peppermint sharpens the mind are mixed. Two controlled studies found better memory or attention and less mental fatigue, one found no effect on vigilance, and a 2025 review of the smell studies says no firm conclusion can be drawn yet.	^{100 65 51 106 132 104}
Cognitive Performance	Potential benefit	Mixed findings	Alertness, memory and focus (smelling or swallowing the oil): Studies on whether peppermint sharpens the mind are mixed. Two controlled studies found better memory or attention and less mental fatigue, one found no effect on vigilance, and a 2025 review of the smell studies says no firm conclusion can be drawn yet.	^{100 65 51 106 132 104}
Reduce Fatigue	Potential benefit	Low certainty	Fatigue and sleepiness (aroma): Several small trials in which people smelled peppermint report less tiredness, in cardiac patients, in people with mental exhaustion and in a driving test. Most results come from self-rated scales and single hospitals, and the blends or comparison scents make peppermint's own part hard to judge.	^{83 140 60 106 65}
Energy Boost	Potential benefit	Low certainty	Fatigue and sleepiness (aroma): Several small trials in which people smelled peppermint report less tiredness, in cardiac patients, in people with mental exhaustion and in a driving test. Most results come from self-rated scales and single hospitals, and the blends or comparison scents make peppermint's own part hard to judge.	^{83 140 60 106 65}
Burnout Recovery	Potential benefit	Low certainty	Fatigue and sleepiness (aroma): Several small trials in which people smelled peppermint report less tiredness, in cardiac patients, in people with mental exhaustion and in a driving test. Most results come from self-rated scales and single hospitals, and the blends or comparison scents make peppermint's own part hard to judge.	^{83 140 60 106 65}
Anxiety Support	Potential benefit	Very low certainty	Anxiety and stress (aroma before procedures): Smelling peppermint oil lowered anxiety scores in hospital patients in a few small trials, but peppermint was weaker than lavender in children, and when mixed with lavender it added nothing over lavender alone. The evidence is thin.	^{123 2 46 79 69}
Brain Health	Potential benefit	Very low certainty	Confusion (delirium) after hip or knee surgery in older adults: In one 2025 trial of 178 older adults, smelling peppermint oil after joint replacement surgery was linked to less delirium in the first three days. It is a single, borderline result that needs repeating.	⁷⁹
Healthy Aging	Potential benefit	Very low certainty	Confusion (delirium) after hip or knee surgery in older adults: In one 2025 trial of 178 older adults, smelling peppermint oil after joint replacement surgery was linked to less delirium in the first three days. It is a single, borderline result that needs repeating.	⁷⁹
Endurance Support	Potential benefit	Mixed findings	Exercise effort and performance (oil, aroma, menthol rinse): Results are mixed. Two small studies by one author and one Brazilian trial reported longer time to exhaustion or stronger performance after swallowing the oil, while three other studies found no effect. Peppermint did not make running feel easier in the runner trial, and menthol mouth rinses and gels did not clearly improve performance.	^{91 92 113 97 125 117 142 77 131}
Physical Stamina	Potential benefit	Mixed findings	Exercise effort and performance (oil, aroma, menthol rinse): Results are mixed. Two small studies by one author and one Brazilian trial reported longer time to exhaustion or stronger performance after swallowing the oil, while three other studies found no effect. Peppermint did not make running feel easier in the runner trial, and menthol mouth rinses and gels did not clearly improve performance.	^{91 92 113 97 125 117 142 77 131}
Peak Performance	Potential benefit	Mixed findings	Exercise effort and performance (oil, aroma, menthol rinse): Results are mixed. Two small studies by one author and one Brazilian trial reported longer time to exhaustion or stronger performance after swallowing the oil, while three other studies found no effect. Peppermint did not make running feel easier in the runner trial, and menthol mouth rinses and gels did not clearly improve performance.	^{91 92 113 97 125 117 142 77 131}
Digestive Support	Potential benefit	Mixed findings	Irritable bowel syndrome (enteric-coated oil): Peppermint oil in coated capsules has been tested for irritable bowel syndrome (IBS) in many trials. Older and pooled results say it helps belly pain and overall symptoms. Three newer, larger trials did not meet their main targets, and reviewers rate the overall evidence very low. Side effects such as heartburn are more common than with placebo. Belly pain in children (IBS and functional abdominal pain): A 2026 trial of 228 children found peppermint oil and peppermint sweets worked no better than placebo for stomach pain. A small 2001 trial and a 2017 review had suggested a benefit. The best current evidence is that it does not help beyond placebo in this age group.	^{58 8 67 16 148 103 18 7 141 71 11 76 116 81 86 111 66 13 121 124 6 45 52 57 149 12 98 129 144 134 108 59 63 10 75 135 3 139 25 157 61 118 109 101}
Gut Health	Potential benefit	Mixed findings	Irritable bowel syndrome (enteric-coated oil): Peppermint oil in coated capsules has been tested for irritable bowel syndrome (IBS) in many trials. Older and pooled results say it helps belly pain and overall symptoms. Three newer, larger trials did not meet their main targets, and reviewers rate the overall evidence very low. Side effects such as heartburn are more common than with placebo. Belly pain in children (IBS and functional abdominal pain): A 2026 trial of 228 children found peppermint oil and peppermint sweets worked no better than placebo for stomach pain. A small 2001 trial and a 2017 review had suggested a benefit. The best current evidence is that it does not help beyond placebo in this age group.	^{58 8 67 16 148 103 18 7 141 71 11 76 116 81 86 13 121 124 6 45}
Womens Wellness	Potential benefit	Mixed findings	Nausea and vomiting in pregnancy: Three small trials gave different answers. Peppermint alone matched placebo twice; a lemon and peppermint blend helped from day 2 in one trial. Overall the evidence is weak and mixed. Period pain (primary dysmenorrhoea): A small crossover trial found peppermint capsules lowered period pain and its length, like mefenamic acid, though bleeding fell less. A 2025 review of five trials (499 women) also found less pain, with calls for better studies.	^{61 118 109 85 74 93 120 4 122 126}
Healthy Skin	Potential benefit	Low certainty	Sore, cracked nipples while breastfeeding (applied to skin): Several trials from the same region found peppermint water or gel on the nipples prevented cracks and eased pain, better than lanolin or breast milk in two, though one trial found it no different from lanolin or dexpanthenol cream. Itch (applied to skin): Two small trials found peppermint oil on the skin eased itch in people with liver, kidney or diabetes-related itch and in pregnant women, compared with petrolatum or a placebo oil.	^{93 120 4 122 126 26 5}

B. Body systems

Connected to	Kind of connection	Evidence status	Context	Studies
Digestive system	Adverse effect or risk	Low certainty	Heartburn, reflux worsening, perianal burning, nausea; lower oesophageal sphincter relaxation stated by EU assessment report. Preparation or compound: Peppermint oil capsules; peppermint leaf tea	^{29 30 31 39 58}
Hepatic system	Contraindication	Not enough evidence	EU contraindication in liver disease, cholangitis and bile-duct disorders; precaution rather than demonstrated harm. Preparation or compound: Peppermint oil, oral capsules	²⁹
Respiratory system	Adverse effect or risk	Low certainty	Reflex apnoea and laryngospasm in under-2s (EU); breathing depression in newborn dogs. Preparation or compound: Menthol and peppermint oil, inhaled or applied near the face of infants	^{29 31 102 119}
Skin	Adverse effect or risk	Moderate certainty	Contact allergy found in 0.6% of 28,128 patch-tested patients; oral and lip reactions in case series. Preparation or compound: Peppermint oil on skin, in lip and oral products	^{146 99 29}
Cardiovascular system	Drug or supplement interaction	Low certainty	Felodipine exposure rose to 140% (range 77 to 262%) in 12 healthy volunteers; menthol alone did not change it. Preparation or compound: Peppermint oil with felodipine	^{24 37}
Reproductive system	Contraindication	Not enough evidence	Pregnancy and lactation: safety not established, use not recommended in EU monographs; no fertility data. Preparation or compound: Medicinal peppermint products	^{29 30 102 1}
Immune system	Adverse effect or risk	Low certainty	Allergic reactions including anaphylactic shock listed with unknown frequency. Preparation or compound: Peppermint oil, menthol	^{29 31 102}
Nervous System	Biological association	Low certainty	Studied for: Tension-type headache (oil on the forehead and temples) Studied for: Migraine attacks (nose drops or menthol gel)	^{43 42 44 114 130 80 128 69 100 65 51 106 132 104 83 140 60 123 2 46 79 144 134 108 59 63 10 75 135}
Musculoskeletal System	Biological association	Low certainty	Studied for: Tension-type headache (oil on the forehead and temples) Studied for: Exercise effort and performance (oil, aroma, menthol rinse)	^{43 42 44 91 92 113 97 125 117 142 77 131}
Stress Mood	Biological association	Very low certainty	Studied for: Anxiety and stress (aroma before procedures)	^{123 2 46 79 69}
Respiratory System	Biological association	Mixed findings	Studied for: Exercise effort and performance (oil, aroma, menthol rinse)	^{91 92 113 97 125 117 142 77 131}
Digestive System	Biological association	Mixed findings	Studied for: Irritable bowel syndrome (enteric-coated oil) Studied for: Belly pain in children (IBS and functional abdominal pain)	^{58 8 67 16 148 103 18 7 141 71 11 76 116 81 86 111 66 13 121 124 6 45 52 57 149 12 98 129 144 134 108 59 63 10 75 135 3 139 25 157 61 118 109 101}
Reproductive System	Biological association	Mixed findings	Studied for: Nausea and vomiting in pregnancy Studied for: Period pain (primary dysmenorrhoea)	^{61 118 109 85 74 93 120 4 122 126}
Integumentary System	Biological association	Low certainty	Studied for: Sore, cracked nipples while breastfeeding (applied to skin) Studied for: Itch (applied to skin)	^{93 120 4 122 126 26 5}

C. Body parts and organs

Connected to	Kind of connection	Evidence status	Context	Studies
Gut	Adverse effect or risk	Low certainty	Perianal burning and overdose bowel effects including rectal ulceration (EU monograph). Preparation or compound: Peppermint oil	^{29 39}
Liver	Biological association	Very low certainty	A safety relationship, not a benefit: animal liver toxicity at high doses; no peppermint liver-injury cases found; liver disease contraindicates the oral capsules. Preparation or compound: Pulegone and menthofuran in peppermint oil	^{29 31 138}

D. Symptoms

Connected to	Kind of connection	Evidence status	Context	Studies
Irritable bowel syndrome (adults)	Potential benefit	Low certainty	Older trials and pooled reviews favour coated oil, rated very low quality; the largest recent trials missed their main goals. Preparation or compound: Enteric-coated peppermint oil, about 180 to 182 mg per dose, 4 to 8 weeks	^{58 8 148 103}
Belly pain in children	Potential benefit	Low certainty	A 2026 trial of 228 children found no benefit over placebo. Preparation or compound: Peppermint oil capsules or sweets	^{141 71}
Indigestion (functional dyspepsia)	Potential benefit	Moderate certainty	A 2023 Cochrane review rated the peppermint and caraway mix as moderate certainty for global symptoms; peppermint alone was not tested. Preparation or compound: Peppermint oil 90 mg plus caraway oil 50 mg, coated capsule, twice a day for 4 weeks	^{17 76 81}
Tension headache	Potential benefit	Low certainty	One 1996 crossover trial of 41 adults: 10% oil on the forehead matched 1,000 mg paracetamol. Preparation or compound: 10% peppermint oil in ethanol on the forehead and temples	^{43 42}
Nausea (after surgery and chemotherapy)	Potential benefit	Low certainty	Small, mixed trials; a 2024 review rated the aroma evidence low. Preparation or compound: Inhaled peppermint oil	^{144 134 25 54}
Anxiety and mental tiredness	Potential benefit	Very low certainty	Thin, small trials; lavender was stronger than peppermint in children. Preparation or compound: Inhaled peppermint oil	¹⁰⁴

I. Biomarkers

Connected to	Kind of connection	Evidence status	Context	Studies
Headache pain intensity	Biological association	Low certainty	Measured in trials: lowered. A lab change is not the same as a health benefit.	^{43 114 130 69}
Cognitive task performance	Biological association	Very low certainty	Measured in trials: mixed. A lab change is not the same as a health benefit.	^{65 100 51 132}
Rated fatigue and sleepiness	Biological association	Low certainty	Measured in trials: lowered. A lab change is not the same as a health benefit.	^{83 140 60}
Pupil fatigue oscillation (sleepiness index)	Biological association	Very low certainty	Measured in trials: lowered. A lab change is not the same as a health benefit.	¹⁰⁶
EEG alpha/beta ratio (driving fatigue)	Biological association	Very low certainty	Measured in trials: lowered. A lab change is not the same as a health benefit.	⁶⁰
Rated anxiety and stress	Biological association	Very low certainty	Measured in trials: lowered. A lab change is not the same as a health benefit.	^{123 2 46 79}
Heart rate and blood pressure (during anxiety trials)	Biological association	Very low certainty	Measured in trials: mixed. A lab change is not the same as a health benefit.	^{123 2}
Postoperative delirium (3 days)	Biological association	Very low certainty	Measured in trials: lowered. A lab change is not the same as a health benefit.	⁷⁹
Time to exhaustion	Biological association	Very low certainty	Measured in trials: mixed. A lab change is not the same as a health benefit.	^{97 91 125 113}
Perceived effort (RPE) and thermal sensation	Biological association	Low certainty	Measured in trials: no-change. A lab change is not the same as a health benefit.	^{97 142 131}
Colonic spasm score during colonoscopy	Biological association	Low certainty	Measured in trials: mixed. A lab change is not the same as a health benefit.	^{13 121 124 45}
Time to reach the caecum during colonoscopy	Biological association	Low certainty	Measured in trials: mixed. A lab change is not the same as a health benefit.	^{121 124 6}
Adenoma detection rate at colonoscopy	Biological association	Very low certainty	Measured in trials: mixed. A lab change is not the same as a health benefit.	^{13 121 45}
Time for gastric contraction rings to disappear at endoscopy	Biological association	Low certainty	Measured in trials: lowered. A lab change is not the same as a health benefit.	⁵²
Simultaneous contractions of the food pipe	Biological association	Very low certainty	Measured in trials: lowered. A lab change is not the same as a health benefit.	¹¹¹
Time to first bowel sound and first gas after surgery	Biological association	Not enough evidence	Measured in trials: lowered. A lab change is not the same as a health benefit.	¹⁰¹

J. Genes, receptors and enzymes

Connected to	Kind of connection	Evidence status	Context	Studies
TRPM8 (cold and menthol receptor)	Preliminary mechanism	Animal	Cloned in 2002 as the receptor activated by menthol and cool temperatures; deleted in mice, cold sensing is strongly reduced (p11882888, p11893340, p17538622)	^{90 110 14}
TRPA1	Preliminary mechanism	In vitro	Menthol activates TRPA1 at low concentrations and blocks it at higher ones in cells; also linked to menthol responses in mouse trigeminal neurons (p17855602)	⁶²
L-type calcium channel (CACNA1C / Cav1.2 is the usual smooth-muscle form; not named in the papers)	Preliminary mechanism	In vitro	Peppermint oil and menthol blocked L-type-dependent gut muscle contraction; the Bay K8644 activator reversed part of the effect in human gut tissue (p2856502, p1646142, p31612595)	^{48 53 72}
HTR3 (serotonin 5-HT3 receptor channel family)	Preliminary mechanism	In vitro	Peppermint oil and (-)-menthol inhibited 5-HT3 channel flow in mouse N1E-115 cells; the subunit was not specified (p21077259)	⁴⁹
CYP3A4	Preliminary mechanism	Human	Peppermint oil, menthol and menthyl acetate are reversible inhibitors in human liver microsomes; felodipine exposure was 140% of control in 12 volunteers (p12235445)	²⁴
CYP2E1	Preliminary mechanism	In vitro	Converts pulegone to menthofuran (Km 29 micromolar) and oxidises menthofuran in human enzyme tests (p10220485)	^{68 137}
CYP1A2	Preliminary mechanism	Mixed findings	Converts pulegone to menthofuran and oxidises menthofuran in human enzyme tests; peppermint tea lowered rat CYP1A2 activity by 24% (EMA, citing Maliakal 2001, not checked in the original) (p10220485)	^{68 153}
CYP2C19	Preliminary mechanism	In vitro	Oxidises pulegone and menthofuran in human enzyme tests (p10220485)	⁶⁸
CYP2A6	Preliminary mechanism	In vitro	Added to the P450s that oxidise menthofuran (p10220485)	⁶⁸
ABCB1 (P-glycoprotein)	Preliminary mechanism	Animal	Not named in the papers I read; EMA reports that peppermint oil tripled peak cyclosporine in rats and that CYP3A inhibition is not the only explanation (EMA, citing Wacher 2002). Treat as a possible, unconfirmed transporter link	¹⁵³
Trigeminal cool receptors in the nose and mouth	Preliminary mechanism	Human	L-menthol made nasal airflow feel more open in 40 volunteers without changing nasal resistance, while its isomers did not (Eccles 1988 and others, via EMA, not read in the originals)	¹⁵³

K. Biological pathways

Connected to	Kind of connection	Evidence status	Context	Studies
Glucuronidation (menthol to menthol glucuronide)	Preliminary mechanism	Human	Main route for menthol in people; enzyme(s) not identified in the sources read; the glucuronide recycles via bile and gut (p10460066, p16121523)	^{36 40}
Monoterpene (menthol) biosynthesis in leaf oil glands	Preliminary mechanism	In vitro	Eight enzyme steps from geranyl diphosphate to (-)-menthol; enzyme activities and gene expression peak in leaves 12-20 days old (p16292524, p10631265)	^{22 88}
Glutathione depletion and pulegone/menthofuran bioactivation	Preliminary mechanism	Animal	Pulegone used up liver glutathione in rats; furan-type reactive intermediates from menthofuran bind liver proteins (p2338648, p1581528)	^{136 137}
Bile secretion (choleresis)	Preliminary mechanism	Animal	Peppermint leaf, flavonoids and menthol raised bile flow in dogs and rats (EMA, older studies)	¹⁵³

L. Active compounds

Connected to	Kind of connection	Evidence status	Context	Studies
Menthol ((-)-menthol)	Biological association	Mixed findings	Opens the cold-and-menthol receptor TRPM8 in cells and is the receptor that makes menthol feel cool (p11882888; p11893340; p17538622). Switches on TRPA1 at low concentrations and blocks it at higher ones (cells; p17855602). Blocks calcium entry through L-type channels in animal gut muscle (about twice as potent as the whole oil per weight, p2856502). Blocks serotonin 5-HT3 receptor channels in cells and rat gut (p21077259). Inhibits human CYP3A4 in test tubes (Ki 87 micromolar, p12235445). In rats, high topical doses reduced pain responses to heat and cold (p20398704). Biosynthesis from limonene takes eight enzyme steps in the oil glands (p16292524). CID 16666 is the (-)-isomer; CID 1254 is menthol without stereochemistry. Preparation or compound: Essential oil (leaf glandular hairs)	^{90 110 14 62 48 49 36 24 70 22 153 156}
Menthone	Biological association	Not enough evidence	Principal companion of menthol in the oil (McKay and Blumberg call menthol and menthone the main volatile components). No separate activity data were read. Preparation or compound: Essential oil	^{89 153}
Isomenthone	Biological association	Not enough evidence	No separate activity data read. CID shown is the racemic isomenthone in PubChem. Preparation or compound: Essential oil	¹⁵³
Neomenthol	Biological association	Human	In nasal inhalation tests in 40 volunteers, L-menthol made airflow feel more open, but its isomers D-isomenthol and D-neomenthol did not (Eccles 1988, as described in EMA, not checked in the original). CID 439263 is (+)-neomenthol; other neomenthol forms have other CIDs. Preparation or compound: Essential oil	^{150 153}
Menthyl acetate	Biological association	In vitro	A reversible inhibitor of human liver CYP3A4 in test tubes (Ki 124 micromolar, p12235445). No other activity read. Preparation or compound: Essential oil	^{24 153}
1,8-Cineole (eucalyptol)	Biological association	Not enough evidence	No peppermint-specific activity data read. In EMA, cineole was tested with peppermint, jasmine and menthol on attention (no significant result, Ilmberger 2001, not checked in the original). Preparation or compound: Essential oil	¹⁵³
Limonene	Biological association	In vitro	The first committed step in menthol biosynthesis: peppermint cyclises geranyl diphosphate into (-)-(4S)-limonene, which the later enzymes convert to menthol (p16292524). CID 22311 is limonene without stereochemistry; (+)-limonene is CID 440917 and the peppermint pathway makes the (-)-form. Preparation or compound: Essential oil	^{22 153}
Menthofuran	Biological association	In vitro	A liver-toxic metabolite of pulegone; further oxidised by human liver enzymes (CYP2E1, CYP1A2, CYP2C19, CYP2A6) to a reactive furan epoxide and a gamma-ketoenal that bind to liver proteins (p10220485; p1581528; p2338648). Safety limits are set for pulegone plus menthofuran, not for either alone (EMA). Preparation or compound: Essential oil	^{68 137 136 38 153}
Pulegone ((R)-(+)-pulegone)	Biological association	Mixed findings	Turned into menthofuran by human CYP2E1, CYP1A2 and CYP2C19 (p10220485); depletes glutathione and is liver-toxic in rats (p2338648). In a human pennyroyal series, 18 ng/mL pulegone and 1 ng/mL menthofuran were found in serum 72 hours after a fatal ingestion (p8633832). EMA accepts up to 37.5 mg a day of pulegone plus menthofuran for an adult (public statement quoted in EMA). Preparation or compound: Essential oil	^{68 136 9 38 153}
Carvone	Biological association	Not enough evidence	Peppermint oil/caraway oil capsules were studied together, so carvone is measured as the caraway marker in that product (p11455677). No peppermint-specific activity. Preparation or compound: Essential oil	^{84 153}
Rosmarinic acid	Biological association	In vitro	Listed as a main leaf phenolic (p16767798; p37959863). Antioxidant in test tubes, not shown to have a benefit from tea in people (McKay and Blumberg: clinical trials of peppermint tea are absent, p16767798). No peppermint-specific human blood levels were read. Preparation or compound: Leaf (water-soluble)	^{33 89 56 153}
Eriocitrin (eriodictyol 7-O-rutinoside)	Biological association	In vitro	Antioxidant in test tubes; high in the cultivar with the greatest total phenols (EMA, citing Dorman 2003, not checked in the original). No human activity data read. Preparation or compound: Leaf (water-soluble)	^{33 153}
Luteolin and its glycosides (luteolin, luteolin 7-O-glucoside, luteolin 7-O-rutinoside, luteolin 7-O-glucuronide)	Biological association	Animal	Luteolin 7-O-rutinoside reduced an antigen-induced nasal response in rats at 100 and 300 mg/kg, and a leaf extract blocked histamine release from rat mast cells (Inoue 2001, as summarised by EMA; animal). Flavonoids from the leaf relaxed isolated guinea-pig gut and increased bile flow in dogs (EMA, older studies). Preparation or compound: Leaf	^{33 153}
Hesperidin	Biological association	Not enough evidence	No peppermint-specific activity data read. Preparation or compound: Leaf	^{89 56}
Menthol glucuronide (body metabolite, not in the plant)	Biological association	Human	The main bile metabolite, which is recycled between gut and liver (enterohepatic circulation) (p16121523). Measuring it in blood is how peppermint-oil release is tracked in people (p30284674; p34528282). Preparation or compound: Made in the body from menthol	^{36 40 147 127 105}

Each connection is stored with the ingredient, the connected record, the kind of connection, the evidence status, the supporting studies, the preparation or compound involved, and a review date (last reviewed October 24, 2026).

Evidence at a glance: what changed in 16 lab markers

Tap a number to show only those markers. Counts are markers, not people.

Other916

The evidence

The research centre for Peppermint. Every record here was checked against PubMed or the publisher's page; we never list a study we have not verified.

Evidence by outcome

Bars show how many studies we found for each outcome, not how well it works. People are added up across trials only (reviews are not added, to avoid double counting).

How we rate evidence

High certainty

Several well-run trials or reviews agree; further research is unlikely to change the picture much.

Moderate certainty

Good trials point the same way, but some doubt remains.

Low certainty

Small, short or inconsistent trials. The finding could change with better research.

Very low certainty

Very little or very weak human data. Treat as a possibility only.

Mixed findings

Trials or reviews disagree with each other.

Not enough evidence

Not enough human research to say either way.

Evidence against

Good research found no benefit, or found harm.

We take the reviewers' own risk-of-bias and GRADE statements where they exist, and otherwise judge from study size, design, consistency, directness and whether a product matches what is sold. Many publications do not make evidence high. Method note: We searched PubMed, NIH NCCIH, NIH LactMed, the EU herbal monographs and assessment report and other sources, opened each source and recorded the study design, people, product, dose and result as reported. Most studies were read as abstracts only; the EU monographs and assessment reports were read in full (the oil dosing was also seen in a 2007 draft). The NIH NCCIH page was read through a summarising tool. The NIH LiverTox, German Commission E and WHO entries could not be read directly, and nothing is claimed about them beyond what is marked. Early history rests on the EU assessment report and is marked as not checked in the originals. No study is cited that we could not verify.

Study library: every study we checked 157

Design Research type Plant part Year from Search

Study	Design	People	Product, dose, length	Result
2006 Peppermint. · PMID 30000911	Authoritative guidance	Breastfeeding mothers	Peppermint (Mentha x piperita), mostly topical on nipples aerial parts Not given Not given	LactMed record (2026-10-15 date shown) says menthol and 1,8-cineole pass into breast milk in small amounts, other components not studied; peppermint is GRAS as a food in the US; large doses can cause heartburn, nausea and vomiting; allergic reactions including headache reported to menthol; peppermint has been used to suppress milk production, shown in vitro and in animals at high doses; if used on nipples, apply after nursing and wipe off before the next feeding. Methods, limits and funding Outcomes: Safety in lactation Limitations: Database summary; no figures. Read: full-text
Abdel Rehim 2025 The effects of lavender, chamomile and peppermint inhalation aromatherapy on dental anxiety in children: A randomized controlled trial. J Dent Sci · PMID 40654405 · DOI	Controlled trial	100 Children aged 6 to 9 having pulp treatment	Peppermint essential oil by nebuliser (vs lavender and chamomile) essential oil (aroma) Nebulised (dose not given in the abstract) During one dental visit · vs No-oil control group	Anxiety score change: control +0.04, peppermint -0.68, lavender -1.80, chamomile -2.04. Peppermint reduced anxiety but less than lavender and chamomile. Oxygen levels did not differ between groups. Mean change in score by group, as listed Methods, limits and funding Outcomes: Dental anxiety (animated emoji scale), pulse rate, oxygen saturation Limitations: Abstract only; full methods, risk of bias and funding not verified. Four groups of about 25 children; a child's own report on an animated emoji scale; peppermint was the weakest of the three oils. Funding and conflicts: Authors declare no conflict of interest Read: abstract
Ahn 2024 Effects of aromatherapy on nausea and vomiting in patients with cancer: A systematic review and meta-analysis of randomized controlled trials. Complement Ther Clin Pract · PMID 38330531 · DOI	Meta-analysis	Adults with cancer (25 trial comparisons across 10 articles)	Aromatherapy (inhalation or massage), several oils including peppermint leaf (essential oil) Varied Varied · vs Control	Aromatherapy reduced nausea but not vomiting alone. Peppermint oil was named as particularly successful in chemotherapy-induced cases. The authors say conclusive evidence is lacking because there are few trials. Overall SMD -0.81; nausea -0.85; vomiting alone -0.24 (not significant). (Overall -1.11 to -0.52; nausea -1.23 to -0.46; vomiting -1.03 to 0.55) Methods, limits and funding Outcomes: Nausea and vomiting in cancer care Limitations: Mixed oils; peppermint-specific effect size not given in abstract; few trials. Read: abstract
Akbari 2014 Effects of menthol essence and breast milk on the improvement of nipple fissures in breastfeeding women. J Res Med Sci · PMID 25364362	Controlled trial	110 First-time breastfeeding mothers with nipple fissures	Menthol essence (peppermint) leaf (essential oil) 4 drops on nipple and areola after each feed 14 days · vs Own breast milk	Pain and fissure severity fell significantly in the menthol group (P<0.001). Pain and fissures improved; control-group results not in abstract. Methods, limits and funding Outcomes: Pain (VAS) and fissure severity Limitations: Control group result not in the abstract; cannot tell how large the difference from milk alone was. Read: abstract
Akhavan Amjadi 2012 The effect of peppermint oil on symptomatic treatment of pruritus in pregnant women. Iran J Pharm Res · PMID 24250539	Controlled trial	96 Pregnant women with itch (pruritus gravidarum), Rasht	Peppermint oil 0.5% in sesame oil leaf (essential oil) 60 mL bottle, applied twice daily 2 weeks · vs Placebo oil	Itch was lower in the peppermint group than with placebo (p=0.003). Lower itch severity (p=0.003). Methods, limits and funding Outcomes: Itch severity (VAS) Limitations: Effect size not in abstract; the authors call for larger studies. Read: abstract
Al Moussawi 2017 The effect of premedication with peppermint oil capsules (Colpermin) prior to colonoscopy: A double blind randomized placebo-controlled trial. Arab J Gastroenterol · PMID 29273467 · DOI	Controlled trial	80 Adults having elective colonoscopy	Enteric-coated peppermint oil capsules (Colpermin) by mouth leaf (essential oil) Capsules 4 hours before the procedure (dose not stated in abstract) Single pre-procedure dose · vs Placebo	No effect on caecal intubation time, tolerance, satisfaction or sedation use. The authors do not support routine use. No difference. Methods, limits and funding Outcomes: Caecal intubation time, patient tolerance, endoscopist satisfaction, sedation use Limitations: Abstract gives no numbers. Read: abstract
Alam 2013 Efficacy of Peppermint oil in diarrhea predominant IBS - a double blind randomized placebo - controlled study. Mymensingh Med J · PMID 23416804	Controlled trial	74 Adults with diarrhoea-predominant IBS (Rome II), hospital study (65 of 74 completed)	Peppermint oil leaf (essential oil) 6 weeks, plus 2 weeks follow-up · vs Placebo	At 6 weeks the pain score was 4.94 (SD 1.30) with peppermint oil vs 6.15 (SD 1.24) with placebo. Two weeks after stopping pain rose to 6.09. Other symptoms and quality of life did not improve significantly. Pain improved only while taking it. Methods, limits and funding Outcomes: Abdominal pain, other IBS symptoms, quality of life Limitations: Small; pain scale not fully described; the abstract states p>0.001 where it likely means p<0.001, so the exact P is not certain. Read: abstract
Alammar 2019 The impact of peppermint oil on the irritable bowel syndrome: a meta-analysis of the pooled clinical data. BMC Complement Altern Med · PMID 30654773 · DOI	Meta-analysis	835 Adults with irritable bowel syndrome (12 randomised trials)	Peppermint oil capsules leaf (essential oil) Varied by trial Varied · vs Placebo	Peppermint oil improved global symptoms and abdominal pain versus placebo; adverse event rates did not differ significantly. Global improvement RR 2.39 (7 trials, 253 vs 254 patients), NNT 3. Abdominal pain improvement RR 1.78 (6 trials, 278 vs 278), NNT 4. Adverse events 9.3% vs 6.1%, RR 1.40. (Global 1.93-2.97; pain 1.43-2.20; adverse events 0.87-2.26) Methods, limits and funding Outcomes: Global symptom improvement, abdominal pain, adverse events Limitations: Pooled earlier, mostly small trials; the newer large trials in this review period had not yet appeared. Duration and dose differ between trials. Registration: PROSPERO CRD42016050917 Read: abstract
Anderson 1996 Pennyroyal toxicity: measurement of toxic metabolite levels in two cases and review of the literature. Ann Intern Med · PMID 8633832 · DOI	Case series	4 Four people who swallowed pennyroyal (Mentha pulegium) plus review of 18 earlier cases	Pennyroyal oil or herb oil and herb At least 10 ml of oil in the review cases with moderate to severe toxicity Acute	One of four patients died; in the fatal case serum 72 h after ingestion held 18 ng/ml pulegone and 1 ng/ml menthofuran; one patient treated with N-acetylcysteine had menthofuran 40 ng/ml at 10 h. The 18 earlier cases showed moderate to severe toxicity at exposures of at least 10 ml of pennyroyal oil. The paper calls pennyroyal a lethal liver toxin. 1 of 4 died Methods, limits and funding Outcomes: Poisoning, pulegone and menthofuran levels Limitations: Pennyroyal is a different mint species with far more pulegone than peppermint; this does not describe peppermint oil. Read: abstract
Anderson 2004 Aromatherapy with peppermint, isopropyl alcohol, or placebo is equally effective in relieving postoperative nausea. J Perianesth Nurs · PMID 14770380 · DOI	Controlled trial	33 Ambulatory surgery patients with nausea in recovery	Inhaled peppermint oil on gauze leaf (essential oil) Vapour held under the nostrils 2 and 5 minutes · vs Isopropyl alcohol or saline	Nausea fell in all groups (from 60.6 to 28.0 mm at 5 minutes) with no difference between peppermint, alcohol and saline. The authors suggest slow deep breathing may explain the benefit. No difference between peppermint and saline. Methods, limits and funding Outcomes: Nausea on a 100-mm scale Limitations: Very small; short-term. Read: abstract
Anheyer 2017 Herbal Medicines for Gastrointestinal Disorders in Children and Adolescents: A Systematic Review. Pediatrics · PMID 28562281 · DOI	Systematic review	1927 Children and adolescents with gastrointestinal disorders (14 trials of various herbs)	Herbal medicines including peppermint oil leaf (essential oil) Varied Varied · vs Placebo or other treatment	The review found evidence for peppermint oil in shortening, easing and reducing the frequency of pain in children with undifferentiated functional abdominal pain, and for fennel in infantile colic. No serious adverse events were reported. The authors say the number of studies was small. This review pre-dates the 2026 trial that found no benefit. No pooled effect size given in the abstract. Methods, limits and funding Outcomes: Effectiveness and safety of herbal treatments Limitations: Few studies per herb; older evidence; peppermint conclusion rests on small trials. Read: abstract
Asao 2003 Spasmolytic effect of peppermint oil in barium during double-contrast barium enema compared with Buscopan. Clin Radiol · PMID 12662951 · DOI	Controlled trial	383 Patients having double-contrast barium enema	Peppermint oil mixed in barium or put in the enema tube leaf (essential oil) 30 mL peppermint oil preparation Single examination · vs Hyoscine injection (Buscopan) or no treatment	Spasm-free examinations: 13.4% no treatment, 38.1% Buscopan, 41.8% peppermint in tube, 37.8% peppermint in barium. Peppermint matched Buscopan, and did better in the caecum and ascending colon. Peppermint vs no treatment: p<0.0005. Methods, limits and funding Outcomes: Absence of colonic spasm on X-ray films Limitations: Group assignment method not fully clear from the abstract (said 'assigned'); setting not detailed. Read: abstract
Aziz 2020 The anti-spasmodic effect of peppermint oil during colonoscopy: a systematic review and meta-analysis. Minerva Gastroenterol Dietol · PMID 31994371 · DOI	Meta-analysis	Adults having colonoscopy (6 studies, one only an abstract)	Peppermint oil (given into the colon or by mouth; studies differed) leaf (essential oil) Varied, not standardised Single dose before or during colonoscopy · vs Placebo or no treatment	Less spasm, less severe spasm and less peristalsis with peppermint oil. Adenoma detection rate was higher, but only two studies measured it. The authors note significant heterogeneity. Any spasm: risk difference -0.39 (P=0.02). Severe spasm: -0.15 (P=0.04). Peristalsis: -0.27 (P<=0.001). Adenoma detection: RR 1.31 (P=0.01). Methods, limits and funding Outcomes: Spasm, severe spasm, peristalsis, adenoma detection rate Limitations: Mixed administration routes and doses; heterogeneity; includes an abstract-only study; later oral-capsule trials were mostly null. Read: abstract
Bautista 2007 The menthol receptor TRPM8 is the principal detector of environmental cold. Nature · PMID 17538622 · DOI	Knockout mouse study animal	TRPM8-deficient mice	n/a	Neurons and nerve fibres from TRPM8-deficient mice had much weaker cold responses; mice had clear deficits telling cold from warm surfaces but still avoided surfaces below 10 C. Methods, limits and funding Outcomes: Cold detection Limitations: Mouse study. Read: abstract
Behrends 2005 Acute lung injury after peppermint oil injection. Anesth Analg · PMID 16192538 · DOI	Case report	1 18-year-old woman	Peppermint oil injected into a vein oil Single event	Fulminant pulmonary oedema and acute lung injury (ARDS criteria) needing ventilator support for 13 days in intensive care after an intravenous injection of peppermint oil; weaned from the ventilator on day 9. Methods, limits and funding Outcomes: Lung injury Limitations: One case; intravenous misuse, not a use of peppermint products. Read: abstract
Black 2020 Efficacy of soluble fibre, antispasmodic drugs, and gut-brain neuromodulators in irritable bowel syndrome: a systematic review and network meta-analysis. Lancet Gastroenterol Hepatol · PMID 31859183 · DOI	Meta-analysis	4644 Adults with IBS (51 randomised trials of soluble fibre, antispasmodics, peppermint oil or gut-brain medicines)	Peppermint oil capsules (one of several treatments compared) leaf (essential oil) Varied by trial 4 to 12 weeks · vs Placebo and other treatments (network meta-analysis)	Peppermint oil ranked first for global symptoms; tricyclic antidepressants ranked first for abdominal pain. No significant difference between active treatments on direct or indirect comparison. Only 13 of 51 trials were at low risk of bias. Peppermint oil, failure to improve global symptoms: RR 0.63, P-score 0.84. Tricyclic antidepressants: RR 0.66. (0.48-0.83 (peppermint oil, global symptoms)) Methods, limits and funding Outcomes: Failure to improve global IBS symptoms and abdominal pain Limitations: Authors state there is considerable uncertainty because many trials were weak; long-term effects unknown. Read: abstract
Báez 2023 Non-Chinese herbal medicines for functional dyspepsia. Cochrane Database Syst Rev · PMID 37323050 · DOI	Systematic review	4477 Functional dyspepsia; 41 trials, 27 herbal medicines	Non-Chinese herbal medicines incl. STW5, peppermint plus caraway oil, turmeric unspecified varied about 4 weeks · vs Placebo or other treatments	Peppermint plus caraway oil: large global improvement (SMD -0.87), moderate certainty; STW5: very uncertain SMD -0.87; RR improvement 1.53 (95% CI -1.15 to -0.58; 1.30 to 1.81) Methods, limits and funding Outcomes: Global symptoms, adverse events, quality of life Limitations: Peppermint-caraway data from 2 to 3 studies Read: abstract
Cappello 2007 Peppermint oil (Mintoil) in the treatment of irritable bowel syndrome: a prospective double blind placebo-controlled randomized trial. Dig Liver Dis · PMID 17420159 · DOI	Controlled trial	57 Adults with IBS (Rome II) after excluding bacterial overgrowth, lactose intolerance and coeliac disease	Enteric-coated peppermint oil capsules leaf (essential oil) Two capsules twice daily (milligrams not stated in abstract) 4 weeks, plus 4 weeks follow-up · vs Placebo	At 4 weeks 75% of the peppermint oil group had more than a 50% drop in total symptom score versus 38% with placebo (P<0.009). Score stayed lower 4 weeks after stopping (1.60 vs 2.19 at start). 75% vs 38% responders (P<0.009). Methods, limits and funding Outcomes: Total IBS symptom score Limitations: Small trial; short; older trial from a single group. Read: abstract
Cash 2016 A Novel Delivery System of Peppermint Oil Is an Effective Therapy for Irritable Bowel Syndrome Symptoms. Dig Dis Sci · PMID 26319955 · DOI	Controlled trial	72 Adults with IBS-M or IBS-D (Rome III)	Sustained-release small-intestine peppermint oil unspecified three times a day (mg not in abstract) 4 weeks · vs Identical placebo	40% fall vs 24.3% with placebo P=0.0246 Methods, limits and funding Outcomes: Change in Total IBS Symptom Score Limitations: Company-connected author listed Read: abstract
Chumpitazi 2018 Review article: the physiological effects and safety of peppermint oil and its efficacy in irritable bowel syndrome and other functional disorders. Aliment Pharmacol Ther · PMID 29372567 · DOI	Narrative review	Literature on peppermint oil physiology and trials	n/a	Mechanisms proposed include smooth-muscle relaxation (calcium channel blockade or nerve effects), visceral sensitivity modulation via TRP channels, antimicrobial and anti-inflammatory effects. Placebo-controlled studies support use in IBS, functional dyspepsia, childhood abdominal pain and post-operative nausea; few adverse effects reported. Methods, limits and funding Outcomes: Mechanisms, safety and efficacy Limitations: Narrative review (search to July 2017); predates the largest recent IBS trials. Read: abstract
Coderre 2010 Probable warfarin interaction with menthol cough drops. Pharmacotherapy · PMID 20030479 · DOI	Case report	1 46-year-old man on warfarin for venous thromboembolism	Menthol cough drops, 8 to 10 a day menthol 8-10 drops a day About 3 weeks	INR fell from 2.6 to 1.6 on 50 mg a week of warfarin and stayed at 1.6 for 3 weeks despite dose rises; 5 days after stopping the drops it was 2.9, and it later stabilised at 40 mg a week. Naranjo scale: probable. Methods, limits and funding Outcomes: INR Limitations: Single case; menthol cough drops, not peppermint oil. Read: abstract
Croteau 2005 (-)-Menthol biosynthesis and molecular genetics. Naturwissenschaften · PMID 16292524 · DOI	Review of biosynthesis n/a	Peppermint (-)-menthol pathway	n/a	Eight enzyme steps from geranyl diphosphate, starting with (-)-(4S)-limonene, ending in (-)-(1R,3R,4S)-menthol; oil is made and stored in peltate glandular hairs on the plant's surface. Methods, limits and funding Outcomes: Menthol biosynthesis and genes Limitations: Plant-biochemistry review. Read: abstract
Cuffe 2025 Efficacy of dietary interventions in irritable bowel syndrome: a systematic review and network meta-analysis. Lancet Gastroenterol Hepatol · PMID 40258374 · DOI	Meta-analysis	2338 IBS; 28 dietary RCTs	Dietary interventions incl. low FODMAP diet unspecified varied · vs Habitual diet, sham diet and others	Low FODMAP: global RR of not improving 0.51; pain 0.61; bloating 0.55. All comparisons rated low or lower certainty RR 0.51 (global) (95% CI 0.37 to 0.70) Methods, limits and funding Outcomes: Global symptoms, pain, bloating Limitations: Dietary trials hard to blind Read: abstract
Dresser 2002 Evaluation of peppermint oil and ascorbyl palmitate as inhibitors of cytochrome P4503A4 activity in vitro and in vivo. Clin Pharmacol Ther · PMID 12235445 · DOI	Controlled trial	12 12 healthy volunteers (plus human liver microsome lab tests)	Peppermint oil 600 mg with felodipine 10 mg extended-release tablet oil 600 mg once Single dose, 4-way crossover · vs Water; grapefruit juice 300 ml; ascorbyl palmitate 500 mg	Peppermint oil raised felodipine AUC to 140% of the water value (range 77 to 262%, P under .05); grapefruit juice raised it to 173% (range 94 to 280%). Peppermint oil also raised felodipine peak concentration. In the lab, peppermint oil, menthol and menthyl acetate reversibly inhibited CYP3A4 activity. The authors say that peppermint oil may have acted through CYP3A4 but that this needs more study. AUC 140% of water (range 77-262%) Methods, limits and funding Outcomes: Felodipine blood levels Limitations: Small crossover in healthy volunteers; single dose; wide individual range includes a fall; it is not known whether enteric-coated or lower-dose products do the same. Read: abstract
Efe Ertürk 2021 The Effects of Peppermint Oil on Nausea, Vomiting and Retching in Cancer Patients Undergoing Chemotherapy: An Open Label Quasi-Randomized Controlled Pilot Study. Complement Ther Med · PMID 33197662 · DOI	Controlled trial	Adults with cancer having chemotherapy, Turkey	Peppermint oil dabbed between nose and upper lip, plus usual anti-nausea drugs leaf (essential oil) One drop three times a day 5 days after chemotherapy · vs Usual anti-nausea drugs only	Nausea scores were lower in most chemotherapy schedules (for example Folfirinox, mean difference 4.00; P<0.001) but not with cisplatin (P=0.642). Lower nausea in most regimens; no effect with cisplatin. Methods, limits and funding Outcomes: Nausea severity (VAS), frequency of nausea, vomiting and retching Limitations: Quasi-randomised and open label (no blinding); total sample size not stated in the abstract. Read: abstract
Elsaie 2016 Effectiveness of topical peppermint oil on symptomatic treatment of chronic pruritus. Clin Cosmet Investig Dermatol · PMID 27785084 · DOI	Controlled trial	50 Adults with chronic itch from liver, kidney or diabetes	Topical peppermint oil leaf (essential oil) Applied twice daily after hydrating the skin (strength not stated in abstract) 2 weeks · vs Petrolatum	All itch measures improved with peppermint oil and not with petrolatum; total 5-D score favoured peppermint (P<0.05). Better 5-D itch score (P<0.05). Methods, limits and funding Outcomes: 5-D itch scale Limitations: 25 per group; 2 weeks; no strength stated. Read: abstract
European Medicines Agency 2007 Community herbal monograph on Menthae piperitae aetheroleum (DRAFT, 8 May 2007), EMEA/HMPC/349466/2006 EMEA · Source	Authoritative guidance	Adults, adolescents, children	Peppermint leaf or oil leaf or oil see results	Well-established use (draft): enteric-coated capsules for minor gut spasms, gas and abdominal pain, especially in IBS (adults 0.2 to 0.4 ml up to three times a day, before meals, swallowed whole); 10% in ethanol for mild tension-type headache. Traditional use (draft): skin, inhalation (2-4 drops up to three times a day in hot water) and mouth preparations for coughs and colds, muscle pain, itch. Not for children under 8 (oral) or under 2 (traditional uses). n/a Methods, limits and funding Outcomes: Posology and safety statements Limitations: This is the 2007 consultation draft. A later final document exists but was not read, so the numbers may have changed. Read: full-text (PDF text extracted and read)
European Medicines Agency 2016 Public statement on the use of herbal medicinal products containing pulegone and menthofuran (Final, Rev. 1), EMA/HMPC/138386/2005 EMA · Source	Authoritative guidance	Adults, children, pregnancy	Peppermint leaf or oil leaf or oil see results	Limit for pulegone plus menthofuran: 0.75 mg per kg body weight a day (37.5 mg a day for a 50 kg adult) for lifelong use, 75 mg a day for under a year. No confirmed human liver damage from peppermint oil, mint oil or peppermint leaf preparations has been reported. Using Ph. Eur. 8.1 limits the EMA calculates a top oral dose of 1.2 ml oil holds at most 32.97 mg pulegone and 87.92 mg menthofuran. n/a Methods, limits and funding Outcomes: Posology and safety statements Limitations: Regulatory risk calculation based on animal data; pennyroyal oil is the main danger. Read: full-text (PDF text extracted and read)
European Medicines Agency 2020 European Union herbal monograph on Mentha x piperita L., aetheroleum (peppermint oil), Revision 1 (EMA/HMPC/522410/2013) EMA/HMPC monograph, adopted 15 January 2020 · Source	Authoritative guidance		Peppermint oil (Mentha x piperita L., aetheroleum) aerial parts essential oil	Full PDF text read. Well-established use of gastro-resistant oral forms (0.2 to 0.4 ml, 0.6 to 1.2 ml a day) for minor gut spasm, wind and pain especially in irritable bowel syndrome; 10% liquid or semi-solid on forehead and temples for mild tension headache; traditional uses by inhalation, mouth and skin. Contraindications: allergy to peppermint oil or menthol; for the oral gut use, liver disease, cholangitis, achlorhydria, gallstones and other bile-duct disorders; for the traditional uses, children under 2 (menthol can cause reflex apnoea and laryngospasm) and children with a history of seizures. Warnings: oral use not recommended under 8; swallow capsules whole; people with heartburn or hiatal hernia sometimes get worse; avoid acid-lowering medicines and antacids with it. Undesirable effects listed with unknown frequency except heartburn, perianal burning, blurred vision, dry mouth, nausea and vomiting, described as frequent in clinical trials. Overdose can cause severe gut symptoms, diarrhoea, rectal ulceration, seizures, loss of consciousness, apnoea and heart rhythm disturbance. Pregnancy and lactation: not recommended, safety not established. Daily intake of pulegone plus menthofuran must be below 37.5 mg per adult (0.75 mg/kg for children). Methods, limits and funding Limitations: A regulatory summary of other sources; it gives no numbers for how often each effect occurs, apart from calling some effects frequent. Read: full-text
European Medicines Agency 2020 European Union herbal monograph on Mentha x piperita L., folium (peppermint leaf), Revision 1 (EMA/HMPC/572705/2014) EMA/HMPC monograph, adopted 15 January 2020 · Source	Authoritative guidance		Peppermint leaf, herbal tea and tincture leaf	Full PDF text read. Traditional use of leaf tea (1.5 to 3.0 g in 100 to 150 ml boiling water, three times a day for adults) for indigestion and wind. Contraindication: allergy to peppermint leaf or menthol. Patients with gastro-oesophageal reflux should avoid peppermint leaf because heartburn may increase; people with gallstones or bile-duct disorders should be cautious; not recommended under 4; pregnancy and lactation not recommended (safety not established). Interactions: none reported. Overdose: no case reported. Reflux worsening listed as an undesirable effect, frequency not known. Methods, limits and funding Limitations: Traditional-use monograph; adequate genotoxicity, reproductive and carcinogenicity tests for the leaf have not been done, per the monograph. Read: full-text
European Medicines Agency 2020 Assessment report on Mentha x piperita L., folium and aetheroleum, Revision 1 (EMA/HMPC/522409/2013) EMA/HMPC assessment report (101 pages) · Source	Authoritative guidance		Peppermint leaf and peppermint oil leaf and aerial-parts oil	Full PDF text read (101 pages). Safety sections reviewed: leaf and oil relax the lower oesophageal sphincter and can worsen reflux; enteric-coated capsule can break open in the stomach when stomach acid is low (an achlorhydria patient had heartburn and belching); contact allergy and rare anaphylaxis; case reports of lowered INR with menthol cough drops; a rat study of peppermint oil raising cyclosporine; a 12-person study of peppermint oil raising felodipine; menthol and infant apnoea/laryngospasm reflex; a jaundice report in babies exposed to menthol and a caution for G6PD deficiency; overdose cases; and the pulegone and menthofuran limits worked out from a 3-month rat study (no-effect dose 37.5 mg/kg, liver and kidney toxicity). Methods, limits and funding Limitations: Secondary source summarising other papers; several cited papers (for example Nath 2012, Dost and Leiber 1967, Somerville 1984, Rhodes 1976) were not read directly. Read: full-text
European Medicines Agency 2020 European Union herbal monograph on Mentha x piperita L., folium (Final, Revision 1), EMA/HMPC/572705/2014 EMA · Source	Authoritative guidance	Adults and children from 4 years	Peppermint leaf or oil leaf or oil see results	Traditional use for dyspepsia and flatulence. Tea 1.5-3.0 g of leaf in 100-150 ml boiling water three times a day (adults); tincture (1:5; ethanol 45% or 70%) 2.0-3.0 ml three times a day; children 4-11 and adolescents 1.0-2.0 g. See a doctor if symptoms last more than 2 weeks. Heartburn: avoid. Gallstones and bile disorders: caution. Pregnancy and breastfeeding: not recommended (no safety data). n/a Methods, limits and funding Outcomes: Posology and safety statements Limitations: Based on long-standing use only; no efficacy claim from trials. Read: full-text (PDF text extracted and read)
Fecka 2007 Determination of water-soluble polyphenolic compounds in commercial herbal teas from Lamiaceae: peppermint, melissa, and sage. J Agric Food Chem · PMID 18052102 · DOI	HPLC chemical analysis of commercial teas in-vitro	Commercial peppermint, melissa and sage herbal teas	Peppermint leaf infusion (tea bags) leaf one tea bag infusion · vs other Lamiaceae teas	Infusions delivered polyphenols in high amounts, up to 182.2 mg for one peppermint tea bag; luteolin 7-O-beta-glucuronide and lithospermic acid were reported as new compounds for Mentha x piperita. Methods, limits and funding Outcomes: Contents of eriocitrin, luteolin glycosides, rosmarinic acid and others Limitations: Lab analysis of what is in the cup, not a health outcome; tea brands vary. Read: abstract
Ford 2008 Effect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome: systematic review and meta-analysis. BMJ · PMID 19008265 · DOI	Systematic review and meta analysis of RCTs	392 Adults with IBS (4 peppermint-oil trials)	Peppermint oil oil varied at least 1 week · vs placebo	Four trials (392 patients): relative risk of persistent symptoms 0.43; fibre RR 0.87 and antispasmodics RR 0.68 in the same paper. RR 0.43 (0.32-0.59) Methods, limits and funding Outcomes: Persistent symptoms Limitations: Early meta-analysis; small trials. Funding and conflicts: Several authors declare consultancy or speaker fees from pharmaceutical companies (conflict statement in the paper; not itemised here). Read: abstract
Freise 1999 [Peppermint oil-caraway oil fixed combination in non-ulcer dyspepsia--comparison of the effects of enteric preparations]. Pharmazie · PMID 10192108	Controlled trial	223 Non-ulcer dyspepsia	Peppermint oil plus caraway oil, 90/50 mg vs 36/20 mg capsules oil see schedule not in abstract · vs Lower-dose capsule	-3.6 vs -3.3 points; equivalent p<0.001 for each fall Methods, limits and funding Outcomes: Pain intensity Limitations: No placebo; German-language Read: abstract
Gelal 1999 Disposition kinetics and effects of menthol. Clin Pharmacol Ther · PMID 10460066 · DOI	Crossover pharmacokinetic study	12 12 healthy adults	L-menthol capsule or menthol in mint sweets/tea 100 mg capsule; 10 mg in food single dose · vs placebo capsule	Only menthol glucuronide measurable. Plasma half-life 56.2 min (95% CI 51.0-61.5) after the capsule and 42.6 min (32.5-52.7) after sweets/tea; AUC ratio 9.2 (8.2-10.1); urine recovery 45.6% and 56.6%. Heart rate fell less than with placebo; vigor score dropped at 30 minutes. AUC ratio 9.2 (95% CI 8.2-10.1) Methods, limits and funding Outcomes: Menthol and menthol glucuronide in blood and urine; heart rate; mood Limitations: Pure menthol, not peppermint oil; small sample; the sweets/tea arm was not controlled. Read: abstract
Gelal 2005 Effect of menthol on the pharmacokinetics and pharmacodynamics of felodipine in healthy subjects. Eur J Clin Pharmacol · PMID 15592925 · DOI	Controlled trial	10 Healthy volunteers (11 enrolled, 10 completed; blood pressure analysed in 8 women)	Menthol capsules (100 mg then 50, 25 and 25 mg at 2, 5 and 7 hours) with felodipine 10 mg ER tablet menthol 200 mg over the day Single day, crossover · vs Placebo capsules	Felodipine and dehydrofelodipine AUC, peak and time to peak were not markedly changed by menthol, and there were no significant blood pressure or heart rate differences. Methods, limits and funding Outcomes: Felodipine kinetics, blood pressure, heart rate Limitations: Menthol alone, not peppermint oil; 10 people; single day. Read: abstract
Gordon 2015 A decades-long investigation of acute metabolism-based hepatotoxicity by herbal constituents: a case study of pennyroyal oil. Drug Metab Rev · PMID 25512112 · DOI	Narrative review animal	Decades of work on pennyroyal oil	n/a	Summarises pulegone and menthofuran bioactivation by cytochrome P450 in liver injury. Methods, limits and funding Outcomes: Mechanism of pennyroyal hepatotoxicity Limitations: Review focused on pennyroyal. Read: abstract
Grigoleit 2005 Peppermint oil in irritable bowel syndrome. Phytomedicine · PMID 16121521 · DOI	Review	651 Adults and children in 16 trials of 180 to 200 mg enteric-coated peppermint oil	Enteric-coated peppermint oil oil 180-200 mg capsules, 1-2 capsules three times a day Varied (up to 24 weeks suggested) · vs Placebo or antispasmodics	Adverse events were generally mild and transient but specific: heartburn and anal or perianal burning or discomfort, compared with dry mouth and blurred vision for antispasmodic drugs. Overall success averaged 58% (range 39 to 79%) with peppermint oil versus 29% (10 to 52%) with placebo in 12 placebo-controlled studies. Adverse events mild, heartburn and perianal burning typical Methods, limits and funding Outcomes: Efficacy and adverse events Limitations: Narrative review of mostly older trials; no event rates in the abstract. Funding and conflicts: Not stated in abstract Read: abstract
Grigoleit 2005 Pharmacology and preclinical pharmacokinetics of peppermint oil. Phytomedicine · PMID 16121523 · DOI	Narrative pharmacology review animal	Peppermint oil pharmacology and animal pharmacokinetics	n/a	Dose-related gut muscle relaxation through menthol blocking calcium movement; fast absorption and elimination in bile; main metabolite menthol glucuronide with enterohepatic circulation; equal faecal and urinary excretion in rats. Methods, limits and funding Outcomes: Mechanism and PK summary Limitations: Review of mostly animal work. Read: abstract
Gumus 2023 Assessment of Toxic Pyrrolizidine and Tropane Alkaloids in Herbal Teas and Culinary Herbs Using LC-Q-ToF/MS. Foods · PMID 37835225 · DOI	Other in-vitro	Herbal teas and culinary herbs sold in Turkey, including peppermint	Pyrrolizidine and tropane alkaloid testing leaf	Some pyrrolizidine or tropane alkaloids were found in all tested herbal teas and culinary herbs; totals in a group that included peppermint ranged from 4.6 to 1054.5 ng/g. The abstract does not give the peppermint figure alone. 4.6-1054.5 ng/g across the listed products Methods, limits and funding Outcomes: Alkaloid content Limitations: Mixed list of products; compliance with limits not given in the abstract. Read: abstract
Göbel 1994 Effect of peppermint and eucalyptus oil preparations on neurophysiological and experimental algesimetric headache parameters. Cephalalgia · PMID 7954745 · DOI	Controlled trial	32 Healthy volunteers (no headache)	Peppermint oil + ethanol; peppermint + eucalyptus oils + ethanol essential oil (unspecified) Applied with a sponge to large areas of forehead and temples Single applications (crossover) · vs Placebo preparations	Peppermint + eucalyptus + ethanol raised cognitive performance and had a muscle-relaxing and mentally relaxing effect but little effect on pain sensitivity. Peppermint oil + ethanol gave a significant reduction in sensitivity to experimental headache-type pain. Direction only; effect sizes not given in the abstract (null) Methods, limits and funding Outcomes: Cognitive performance, muscle relaxation, mood, and sensitivity to experimental pain Limitations: Abstract only; full methods, risk of bias and funding not verified. Healthy people, not headache patients; laboratory pain tests are an indirect measure of real headache. Read: abstract
Göbel 1996 [Effectiveness of Oleum menthae piperitae and paracetamol in therapy of headache of the tension type]. Nervenarzt · PMID 8805113 · DOI	Controlled trial	41 Adults 18-65 with tension-type headache (164 attacks treated)	Peppermint oil 10% in ethanol 90%, rubbed on forehead and temples essential oil (leaf, unspecified in abstract) Applied to forehead and temples, repeated at 15 and 30 minutes Per headache attack; 4 attacks per person, 1 hour of observation · vs Placebo ethanol solution with traces of peppermint oil; acetaminophen 1,000 mg; placebo tablet	10% peppermint oil lowered headache intensity versus placebo from 15 minutes (p<0.01), lasting the hour. Acetaminophen 1,000 mg also beat placebo (p<0.01). No significant difference between oil and acetaminophen. Both together added a little, but below the significance threshold. No adverse events reported. p-values only in the abstract; effect size not given (null) Methods, limits and funding Outcomes: Headache intensity from a headache diary at 15, 30, 45 and 60 minutes Limitations: Abstract only; full methods, risk of bias and funding not verified. Small crossover trial (41 people); older (1996); the only controlled trial of the 10% oil that the later review cites; the sponsor/funding is not stated in the abstract (the test product is a named commercial preparation); the German-language article was read in English abstract only. Read: abstract
Göbel 2016 [Peppermint oil in the acute treatment of tension-type headache]. Schmerz · PMID 27106030 · DOI	Narrative review	Adults and children over 6 with tension-type headache (as described by the authors)	Peppermint oil 10% in ethanol, topical essential oil Local application Acute treatment of an attack · vs Placebo, aspirin, paracetamol (as described in the review)	The authors state that controlled studies show the topical oil to be significantly better than placebo, with efficacy comparable to aspirin or paracetamol, that 10% solutions are licensed for adults and children above 6, and that it appears in treatment recommendations and guidelines. No numbers in the abstract (null) Methods, limits and funding Outcomes: Overview of controlled studies Limitations: Abstract only; full methods, risk of bias and funding not verified. This is a narrative (non-systematic) review by the clinic that ran the original trials, so it is not an independent check. The statements about licensing and guidelines are the authors' own and were NOT verified against the guidelines themselves in this file. Read: abstract
Han 2021 Oral IBGard™ Before Colonoscopy: A Single-Center Double-Blinded, Randomized, Placebo-Controlled Trial. Dig Dis Sci · PMID 32519140 · DOI	Controlled trial	Adults having screening or surveillance colonoscopy	Oral sustained-release peppermint oil (IBgard) leaf (essential oil) Single oral dose before the procedure (dose not stated in abstract) Single pre-procedure dose · vs Placebo	No difference in spasm scores (insertion 1.23 vs 1.2; withdrawal 1.3 vs 1.23; polypectomy 0.52 vs 0.46) or adenoma detection (47.8% vs 43.1%, p=0.51), even when given more than 60 minutes before. No benefit from oral dosing. Methods, limits and funding Outcomes: Spasm scores at insertion, withdrawal and polypectomy; adenoma detection rate Limitations: Sample size not in abstract; dose timing varied. Read: abstract
Hancı 2025 The Effect of Aromatherapy on Pain and Anxiety Levels Before Breast Biopsy: A Randomized Controlled Trial. Eur J Breast Health · PMID 40390380 · DOI	Controlled trial	135 Women having a breast biopsy	Lavender, or a lavender-peppermint blend, inhaled from a pad essential oil blend (aroma) Pad with oil on the shoulder 20 minutes before the biopsy One session · vs No-aroma control (45 per group)	Anxiety and pain fell more in both aroma groups than control (p<0.05); lavender alone and lavender-peppermint did not differ from each other (p>0.05). Group differences p<0.05 Methods, limits and funding Outcomes: State anxiety inventory and a pain visual analogue scale Limitations: Abstract only; full methods, risk of bias and funding not verified. Peppermint was blended with lavender, so the result cannot be credited to peppermint; since lavender alone did as well, peppermint added nothing measurable here. Funding and conflicts: Authors declare no conflict of interest Read: abstract
Hawrelak 2020 Western herbal medicines in the treatment of irritable bowel syndrome: A systematic review and meta-analysis. Complement Ther Med · PMID 31987249 · DOI	Meta-analysis	IBS; 33 double-blind placebo-controlled trials of Western herbs	Peppermint oil and other herbs (aloe vera, asafoetida, STW5, curcumin plus fennel oil, others) unspecified varied short term · vs Placebo	Peppermint oil efficacious and well tolerated short term; most other positive trials not yet replicated not in abstract Methods, limits and funding Outcomes: IBS symptoms Limitations: Lack of replication for most herbs Read: abstract
Hawthorn 1988 The actions of peppermint oil and menthol on calcium channel dependent processes in intestinal, neuronal and cardiac preparations. Aliment Pharmacol Ther · PMID 2856502 · DOI	Isolated tissue and binding study animal	Guinea-pig ileum, rat/guinea-pig heart muscle, rat brain synaptosomes, chick retinal neurons	Peppermint oil and menthol oil IC50 about 7.7-28.1 micrograms/mL in ileum	Menthol was about twice as potent as the oil; both inhibited nitrendipine binding competitively and blocked calcium entry; the authors say calcium blockade may not be the only mechanism. Methods, limits and funding Outcomes: Calcium-channel-dependent responses Limitations: Animal tissue and cells; concentrations in micrograms/mL. Read: abstract
Heimes 2011 Mode of action of peppermint oil and (-)-menthol with respect to 5-HT3 receptor subtypes: binding studies, cation uptake by receptor channels and contraction of isolated rat ileum. Phytother Res · PMID 21077259 · DOI	Cell and isolated tissue study in-vitro	Mouse N1E-115 cells; rat ileum	Peppermint oil and (-)-menthol oil not given in abstract	Both reduced guanidinium influx through 5-HT3 channels and serotonin-induced ileum contraction but did not displace a 5-HT3 blocker, suggesting a different (modulatory) site. Methods, limits and funding Outcomes: 5-HT3 receptor effects Limitations: Cell and animal tissue. Read: abstract
Herro 2010 Mentha piperita (peppermint). Dermatitis · PMID 21144345	Review	Review of peppermint in dermatitis	Peppermint oil and leaf preparations oil and leaf	Abstract says numerous allergic contact dermatitis reactions to peppermint oil have been described, many linked to perioral and intraoral disorders, and that frequent application to damaged skin could contribute to sensitisation. Methods, limits and funding Outcomes: Sensitisation Limitations: Short review; abstract only. Read: abstract
Heuberger 2010 The influence of essential oils on human vigilance. Nat Prod Commun · PMID 20923005	Controlled trial	Healthy volunteers (seven experimental groups plus a control group)	Inhaled 1,8-cineole, jasmine absolute, linalyl acetate and peppermint essential oil essential oil (aroma) Inhaled (dose not given in the abstract) Single session · vs Control group, no odour	None of the expected improvements appeared, including for peppermint. Only linalyl acetate (a lavender component) changed reaction times (faster). Within groups, liking of the smell tracked performance. No improvement from peppermint Methods, limits and funding Outcomes: Speed and accuracy on a visual vigilance task; ratings of pleasantness, arousal, stress Limitations: Abstract only; full methods, risk of bias and funding not verified. Group sizes not stated in the abstract. A null result on a task that other studies report as improved. Read: abstract
Hiki 2003 Peppermint oil reduces gastric spasm during upper endoscopy: a randomized, double-blind, double-dummy controlled trial. Gastrointest Endosc · PMID 12665756 · DOI	Controlled trial	100 Patients having upper endoscopy	Peppermint oil solution put into the stomach through the endoscope leaf (essential oil) Dose not stated in abstract Single dose · vs Hyoscine-N-butylbromide injection	Peppermint oil opened the pyloric ring more and reduced contraction more than hyoscine. Time to settle was 97.1 s vs 185.9 s (p<0.0001). No significant side effects with peppermint oil; hyoscine caused dry mouth, blurred vision and urinary retention. Faster relief of gastric spasm than hyoscine. Methods, limits and funding Outcomes: Pyloric ring opening and contraction, time for antral contraction ring to disappear, side effects Limitations: Comparison was with an injection, not a placebo alone (double-dummy design with placebo solutions). Read: abstract
Hills 1991 The mechanism of action of peppermint oil on gastrointestinal smooth muscle. An analysis using patch clamp electrophysiology and isolated tissue pharmacology in rabbit and guinea pig. Gastroenterology · PMID 1646142 · DOI	Isolated tissue and patch clamp study animal	Guinea-pig colon and taenia coli; rabbit jejunum smooth muscle cells	Peppermint oil oil IC50 15.2-25.9 micrograms/mL	Relaxed carbachol-contracted taenia coli (IC50 22.1 micrograms/mL), blocked contractions to several agonists, and reduced calcium currents in a way like dihydropyridines; concluded it reduces calcium influx. Methods, limits and funding Outcomes: Mechanism of gut relaxation Limitations: Animal tissue; no human data. Read: abstract
Hines 2018 Aromatherapy for treatment of postoperative nausea and vomiting. Cochrane Database Syst Rev · PMID 29523018 · DOI	Systematic review	1036 Postoperative nausea and vomiting; 16 studies, all aromatherapies	Aromatherapy (incl. peppermint products, blends) unspecified varied varied · vs Placebo or standard antiemetics	No clear drop in nausea severity vs placebo (SMD -0.22) but fewer rescue antiemetics (RR 0.60) SMD -0.22; RR 0.60 (95% CI -0.63 to 0.18; 0.37 to 0.97) Methods, limits and funding Outcomes: Nausea severity, rescue antiemetics Limitations: Low to very low certainty; all aromatherapies pooled Read: abstract
Hu 2011 Effect of ginger on gastric motility and symptoms of functional dyspepsia. World J Gastroenterol · PMID 21218090 · DOI	Controlled trial	11 Functional dyspepsia	Ginger capsules rhizome 1.2 g in a single dose single dose · vs Placebo, crossover	Faster half-emptying (12.3 vs 16.1 min) but no change in symptoms P<=0.05 Methods, limits and funding Outcomes: Gastric emptying and symptoms Limitations: Eleven people Read: abstract
Hudz 2023 Mentha piperita: Essential Oil and Extracts, Their Biological Activities, and Perspectives on the Development of New Medicinal and Cosmetic Products. Molecules · PMID 37959863 · DOI	Narrative review mixed	Literature on Mentha piperita oil and extracts	Peppermint oil and extracts leaf and oil varied varied · vs varied	Phenolics include caffeic acid, rosmarinic acid, eriocitrin, luteolin derivatives and hesperidin. Gram-positive bacteria were more sensitive than Gram-negative; oil had both antioxidant and pro-oxidant effects depending on test. Reduced TNF-alpha and IL-6 in vitro and paw swelling in rats. Methods, limits and funding Outcomes: Composition, activities and product potential Limitations: Narrative review aimed at product development; mostly lab and animal evidence. Read: abstract
Imagawa 2012 Peppermint oil solution is useful as an antispasmodic drug for esophagogastroduodenoscopy, especially for elderly patients. Dig Dis Sci · PMID 22562537 · DOI	Observational cohort	8269 Patients having upper endoscopy (8,269 procedures)	Peppermint oil solution during endoscopy leaf (essential oil) Single procedure · vs Hyoscine butylbromide, glucagon, or no antispasmodic	Similar overall to hyoscine (4.025 vs 4.063). In patients under 70 peppermint scored lower (3.923 vs 4.062, P<0.001); in patients 70 and over it was similar to hyoscine (4.073 vs 4.064) and better than glucagon. Equivalent overall; less effective in younger patients. Methods, limits and funding Outcomes: Antispasmodic score (1-5) Limitations: Not randomised; choice of drug not random; large but observational. Read: abstract
Ingrosso 2022 Systematic review and meta-analysis: efficacy of peppermint oil in irritable bowel syndrome. Aliment Pharmacol Ther · PMID 35942669 · DOI	Meta-analysis	1030 Adults with irritable bowel syndrome (10 randomised trials)	Peppermint oil (capsules; trial products differed) leaf (essential oil) Varied by trial Trials of roughly 2 to 12 weeks (not stated in abstract) · vs Placebo	Peppermint oil beat placebo for global symptoms and abdominal pain, with more adverse events. Authors rated the quality of evidence very low. Global symptoms not improving: RR 0.65 (NNT 4). Abdominal pain not improving: RR 0.76 (NNT 7). Any adverse event: RR 1.57. (Global RR 0.43-0.98 (NNT 95% CI 2.5-71); pain RR 0.62-0.93 (NNT 4-24); adverse events RR 1.04-2.37) Methods, limits and funding Outcomes: Global IBS symptoms, abdominal pain, adverse events Limitations: Few trials, small, some at risk of bias; the authors say recent trials cast doubt on earlier results. Duration and dose differ between trials. Read: abstract
Ishikawa 2025 Effect of aromatherapy with peppermint, ginger, and lavender on postoperative nausea severity after oral surgery under general anaesthesia: A single-blind randomized controlled trial. Complement Ther Med · PMID 40154579 · DOI	Controlled trial	182 Adults after oral surgery under general anaesthesia, Japan (57 had nausea and were treated)	Inhaled aromatherapy of peppermint, ginger and lavender together leaf (essential oil) plus ginger and lavender oils 1% of each (0.01 mL pure oil per dose) At onset of nausea · vs Purified water	Aromatherapy lowered nausea severity (p<0.001) and raised satisfaction. Antiemetic use 30.77% vs 52.38% (not significant). No adverse events. Nausea lower (p<0.001). Methods, limits and funding Outcomes: Change in nausea severity Limitations: Mixed oils, so peppermint alone cannot be separated; only 57 treated; single blind. Registration: jRCTs 01121002 Read: abstract
Jiang 2024 Scented Solutions: Examining the Efficacy of Scent Interventions in Mitigating Driving Fatigue. Sensors (Basel) · PMID 38676001 · DOI	Controlled trial	Drivers in a driving task (number not given in the abstract)	Peppermint, grapefruit or lavender scent essential oil (aroma) Not given in the abstract During a fatiguing driving task · vs No-scent control group	All three scents lowered rated and EEG-measured driving fatigue versus control. Grapefruit worked fastest and lavender lasted longest per the authors. Significant differences; numbers not in the abstract (null) Methods, limits and funding Outcomes: Karolinska Sleepiness Scale and EEG ratio R(alpha/beta) Limitations: Abstract only; full methods, risk of bias and funding not verified. Driving task, probably a simulator (not stated in the abstract); sample size not in the abstract; peppermint was not singled out as better than the others. Funding and conflicts: Authors declare no conflicts of interest Read: abstract
Joulaeerad 2018 Effect of Aromatherapy with Peppermint Oil on the Severity of Nausea and Vomiting in Pregnancy: A Single-blind, Randomized, Placebo-controlled trial. J Reprod Infertil · PMID 29850445	Controlled trial	56 Pregnant women, 6-20 weeks, mild to moderate nausea and vomiting	Inhaled peppermint oil leaf (essential oil) 4 days · vs Placebo	Nausea fell in both groups (p<0.001) but the groups did not differ. No difference from placebo. Methods, limits and funding Outcomes: Pregnancy-Unique Quantification of Emesis (PUQE) score Limitations: Small; short; single-blind. Read: abstract
Karashima 2007 Bimodal action of menthol on the transient receptor potential channel TRPA1. J Neurosci · PMID 17855602 · DOI	Cell and neuron electrophysiology in-vitro	Cells expressing TRPA1; mouse trigeminal neurons	Menthol sub-micromolar to high concentrations	Submicromolar to low-micromolar menthol activates TRPA1; higher concentrations reversibly block it. Methods, limits and funding Outcomes: Menthol effect on TRPA1 Limitations: Cell work. Read: abstract
Karsten 2020 Effects of Peppermint Aromatherapy on Postoperative Nausea and Vomiting. J Perianesth Nurs · PMID 32782076 · DOI	Controlled trial	Patients after surgery	Inhaled peppermint aromatherapy plus usual care leaf (essential oil) · vs Usual care only	No statistically significant difference (P=.28). Many patients liked it and reported less nausea. No significant difference. Methods, limits and funding Outcomes: Postoperative nausea and vomiting incidence, antiemetic use Limitations: Quasi-experimental; small; no blinding. Read: abstract
Kassebaum 2005 Possible warfarin interaction with menthol cough drops. Ann Pharmacother · PMID 15644472 · DOI	Case report	1 57-year-old man on warfarin awaiting cardioversion	Menthol cough drops (Halls) menthol About 1 week	INR fell from a stable 2.28 to 2.68 to 1.45 about a week after starting menthol cough drops during a flu-like illness; warfarin was raised to 53 mg a week, then returned to the previous dose after the drops were stopped and INR stayed stable. Authors judged it a possible interaction. Methods, limits and funding Outcomes: INR Limitations: Single case; menthol only, not peppermint oil; illness was a confounder. Read: abstract
Kennedy 2018 Volatile Terpenes and Brain Function: Investigation of the Cognitive and Mood Effects of Mentha x Piperita L. Essential Oil with In Vitro Properties Relevant to Central Nervous System Function. Nutrients · PMID 30087294 · DOI	Controlled trial	24 Healthy adults, mean age 25.2	Peppermint essential oil capsules (swallowed, not inhaled) essential oil (leaf, unspecified) 50 microlitres or 100 microlitres, single dose Single doses, tests at 1, 3 and 6 hours · vs Placebo capsule (balanced crossover)	100 microlitres improved Rapid Visual Information Processing at 1 and 3 hours. Both doses reduced fatigue and improved Serial 3s subtraction at 3 hours. Specific numbers not in the abstract (null) Methods, limits and funding Outcomes: Rapid Visual Information Processing, Serial 3s subtraction, mood and mental fatigue scales Limitations: Abstract only; full methods, risk of bias and funding not verified. 24 young volunteers, single doses; improvements were seen on a few of many tests (multiple comparisons not discussed in the abstract); swallowing the pure oil is a pharmacology study and is not advice to do it at home. Funding and conflicts: Authors declare no conflict of interest Read: abstract
Khalaf 2019 Impact of Peppermint Therapy on Dysphagia and Non-cardiac Chest Pain: A Pilot Study. Dig Dis Sci · PMID 30771044 · DOI	Case series	38 Patients referred for oesophageal motility testing with trouble swallowing or chest pain	Concentrated peppermint tablets leaf (essential oil) Two dissolvable tablets before meals (swallowing trouble) or as needed (chest pain)	24 of 38 (63%) reported improvement (12 much better, 12 slightly better); 14 had no change; none were worse. Best response in distal oesophageal spasm (83%) and outflow obstruction (100%). 63% improved; no control group. Methods, limits and funding Outcomes: Patient-reported symptom response on a 5-point scale Limitations: Retrospective chart review; no control; patient-reported; small subgroups. Read: abstract
Khanna 2014 Peppermint oil for the treatment of irritable bowel syndrome: a systematic review and meta-analysis. J Clin Gastroenterol · PMID 24100754 · DOI	Meta-analysis	726 Adults with active IBS (9 randomised trials)	Enteric-coated peppermint oil capsules leaf (essential oil) Varied by trial At least 2 weeks per trial · vs Placebo	Peppermint oil beat placebo for global symptoms and pain over the short term. Adverse events were more common but mild and short-lived; heartburn was the most common. Global improvement RR 2.23 (5 studies, 392 patients). Pain improvement RR 2.14 (5 studies, 357 patients). (Global 1.78-2.81; pain 1.64-2.79) Methods, limits and funding Outcomes: Global improvement, abdominal pain, adverse events Limitations: Short treatment (as little as 2 weeks); long-term effects not assessed; older trials only. Read: abstract
Khojasteh-Bakht 1999 Metabolism of (R)-(+)-pulegone and (R)-(+)-menthofuran by human liver cytochrome P-450s: evidence for formation of a furan epoxide. Drug Metab Dispos · PMID 10220485	Human enzyme study in-vitro	Expressed human liver cytochrome P450 enzymes	(R)-(+)-pulegone and (R)-(+)-menthofuran	CYP2E1, CYP1A2 and CYP2C19 made menthofuran from pulegone (Km 29, 94 and 31 micromolar); the same plus CYP2A6 oxidised menthofuran to 2-hydroxymenthofuran via a furan epoxide. Methods, limits and funding Outcomes: Which enzymes make menthofuran Limitations: Enzyme study. Read: abstract
Kingsley 2023 Randomized Trial Examining Efficacy of Mentha piperita in Reducing Chronic Headache Discomfort in Youth. Pain Manag Nurs · PMID 37730471 · DOI	Controlled trial	46 Adolescents (mean age 15.2, 89% female) with a primary headache disorder	Peppermint oil added to a foot bath (aromatherapy) essential oil Brief foot bath plus peppermint oil (amount not given in the abstract) Single brief session · vs Foot bath alone	Both groups reported less pain. Adding peppermint oil did not significantly improve pain or anxiety compared with the foot bath alone. Anxiety fell a little more in the oil group than the control group (p=0.03) but pain did not. No adverse events; 95.5% liked and would recommend it. Added effect of peppermint not significant for pain; no effect sizes in the abstract (null) Methods, limits and funding Outcomes: Heart rate, self-rated pain, anxiety and satisfaction at baseline, mid and end of session Limitations: Abstract only; full methods, risk of bias and funding not verified. Small single-centre trial; very short; the relaxing foot bath did most of the work; mostly female; a result for pain not anxiety was mixed. Funding and conflicts: Funded by a Katharine B. Richardson Foundation Award; authors declare no competing interests Read: abstract
Klein 2010 Topical application of L-menthol induces heat analgesia, mechanical allodynia, and a biphasic effect on cold sensitivity in rats. Behav Brain Res · PMID 20398704 · DOI	Rat behaviour study animal	Rats (topical L-menthol 0.01-40%)	L-menthol on the paw 0.01-40% · vs vehicle	40% menthol lengthened the response time to noxious heat and also lowered the touch threshold; low concentrations increased cold avoidance, high ones reduced it. Methods, limits and funding Outcomes: Heat, cold and touch sensitivity Limitations: Rat study; supports TRPM8 as a pain target, not a human result. Read: abstract
Kline 2001 Enteric-coated, pH-dependent peppermint oil capsules for the treatment of irritable bowel syndrome in children. J Pediatr · PMID 11148527 · DOI	Controlled trial	42 Children with IBS	Enteric-coated, pH-dependent peppermint oil capsules leaf (essential oil) 2 weeks · vs Placebo	75% of those on peppermint oil had less severe IBS-related pain after 2 weeks. 75% with reduced pain severity (the abstract gives no comparator percentage). Methods, limits and funding Outcomes: Severity of pain associated with IBS Limitations: Very small; 2 weeks; abstract is brief and does not give the placebo result. Read: abstract
Krueger 2020 Peppermint and caraway oils have muscle inhibitory and pro-secretory activity in the human intestine in vitro. Neurogastroenterol Motil · PMID 31612595 · DOI	Human tissue in vitro study in-vitro	255 255 small and large intestine preparations from 73 surgical patients	Peppermint oil and caraway oil oil IC50 17-90 micrograms/mL for peppermint oil	Both oils relaxed muscle and reduced phasic contractions at all sites, independent of nerves; the contraction-reducing effect was prevented by the L-type calcium channel activator Bay K8644; both increased epithelial secretion. Methods, limits and funding Outcomes: Muscle contraction and secretion Limitations: Isolated surgical tissue; not an effect in a living gut. Read: abstract
Lacy 2021 ACG Clinical Guideline: Management of Irritable Bowel Syndrome. Am J Gastroenterol · PMID 33315591 · DOI	Authoritative guidance	Adults with IBS	ACG 2021 IBS guideline	The abstract recommends a limited low FODMAP diet trial and suggests gut-directed psychotherapy. Peppermint oil is not named in the abstract; the full text was not read. n/a Methods, limits and funding Outcomes: Diagnosis and treatment recommendations Limitations: Full text not read Read: abstract
Lagzian 2025 The Effects of Peppermint on Menstrual Disorders: A Systematic Review of Randomized Controlled Trials. Iran J Nurs Midwifery Res · PMID 41311590 · DOI	Systematic review	499 Women with primary dysmenorrhoea or premenstrual symptoms (5 randomised trials)	Peppermint (Mentha piperita) leaf (essential oil) Varied Varied · vs Placebo or other treatment	Three trials rated high quality and two low. Pain severity, cognitive function and gastrointestinal symptoms improved. The authors call for higher-quality trials. No pooled effect size in the abstract. Methods, limits and funding Outcomes: Pain, cognitive symptoms, gastrointestinal symptoms Limitations: Few trials; mixed quality; two conditions combined (dysmenorrhoea and PMS). Read: abstract
Lane 2012 Examination of the effectiveness of peppermint aromatherapy on nausea in women post C-section. J Holist Nurs · PMID 22034523 · DOI	Controlled trial	35 Women with nausea after Caesarean section	Inhaled peppermint spirits leaf (essential oil) Measured 2 and 5 minutes after · vs Inert green water or standard antiemetics	Nausea was lower with peppermint spirits than with placebo or standard antiemetics at 2 and 5 minutes. Lower nausea scores (numbers not in abstract). Methods, limits and funding Outcomes: Nausea on a 6-point scale Limitations: Small; only 35 women developed nausea; peppermint spirits not pure oil; short-term. Read: abstract
Li 2019 A Combination of Peppermint Oil and Caraway Oil for the Treatment of Functional Dyspepsia: A Systematic Review and Meta-Analysis. Evid Based Complement Alternat Med · PMID 31827561 · DOI	Meta-analysis	578 Adults with functional dyspepsia (5 randomised trials)	Fixed peppermint oil and caraway oil combination (POCO) leaf (essential oil) plus caraway oil Varied by trial About 4 weeks (not stated in abstract) · vs Placebo	The combination improved global symptoms and upper-belly pain versus placebo. No significant difference in total adverse events. Authors rate the evidence low or very low quality. Not much or very much improvement: RR 0.59 (NNT 3). Epigastric pain improvement: RR 1.61 (NNT 3). (0.49-0.71; pain 1.28-2.03) Methods, limits and funding Outcomes: Global symptom improvement, epigastric pain, adverse events Limitations: Small trials; the combination cannot show what peppermint oil alone does. Read: abstract
Li 2026 Effects of carbohydrate, caffeine and menthol mouth rinses on exercise performance and ratings of perceived exertion: a systematic review and network meta-analysis. Front Nutr · PMID 42688491 · DOI	Meta-analysis	609 Mostly trained or active people (57 studies, 609 participants)	Menthol, caffeine or carbohydrate mouth rinses (spat out) menthol (isolated compound) Various Various · vs Placebo rinse	Menthol did not differ significantly from caffeine or carbohydrate, and no significant effect of menthol versus placebo is reported in the abstract (caffeine and carbohydrate had significant effects on time to exhaustion). Menthol ranked first in two outcomes (time to complete a fixed amount of work, mean power) but the authors say rankings should not be read as proof of superiority. Menthol versus placebo not significant in the abstract; caffeine SMD 0.57 (0.13 to 1.01) and carbohydrate SMD 0.43 (0.11 to 0.75) for time to exhaustion Methods, limits and funding Outcomes: Time to exhaustion, work done, time for a fixed task, mean power, perceived exertion Limitations: Abstract only; full methods, risk of bias and funding not verified. Menthol mouth rinse is not peppermint tea or oil; mostly small crossover trials of trained people; certainty graded with CINeMA but the grades are not in the abstract. Registration: PROSPERO CRD420261282363 Read: abstract
Liu 1997 Enteric-coated peppermint-oil capsules in the treatment of irritable bowel syndrome: a prospective, randomized trial. J Gastroenterol · PMID 9430014 · DOI	Controlled trial	110 Outpatients with IBS symptoms	Colpermin enteric-coated peppermint oil unspecified 1 capsule three to four times a day before meals 1 month · vs Placebo	Pain eased in 79% vs 43% P<0.05 Methods, limits and funding Outcomes: Pain, distension, stool frequency, gas Limitations: 1997; 101 finished Read: abstract
Liu 2025 Effect of inhalation of peppermint essential oil aromatherapy on postoperative delirium in old patients following major lower limb joint arthroplasty surgery: A randomized controlled trial. Explore (NY) · PMID 41390992 · DOI	Controlled trial	178 Older adults (median age 70) having hip or knee replacement	Peppermint essential oil, inhaled essential oil (aroma) Not given in the abstract Delirium watched for 3 days after surgery · vs Normal saline (inhaled)	Delirium 7.9% with peppermint versus 19.1% with saline (risk ratio 0.412; 95% CI 0.179 to 0.944; P=0.048). Pain at rest and in activity over 3 days and anxiety over 2 days were lower (all P<0.05). RR 0.412; risk difference -0.112 (95% CI 0.179 to 0.944) Methods, limits and funding Outcomes: Delirium within 3 days; pain; anxiety; side effects Limitations: Abstract only; full methods, risk of bias and funding not verified. A single hospital and trial; P=0.048 is borderline; blinding of an aroma is difficult; neither the dose nor the delirium test is in the abstract; replication needed. Funding and conflicts: Authors declare no conflict of interest Read: abstract
Lopresti 2020 Herbal treatments for migraine: A systematic review of randomised-controlled studies. Phytother Res · PMID 32310327 · DOI	Systematic review	People with migraine; 19 randomised studies of nine herbs	Single-ingredient herbs including menthol/peppermint oil various Various Acute or preventive · vs Placebo or active	Across nine herbs the reviewers found preliminary positive findings for menthol and chamomile as an acute treatment, but note that risk of bias was high in many studies and call for better research. No numbers for peppermint specifically in the abstract (null) Methods, limits and funding Outcomes: Migraine outcomes Limitations: Abstract only; full methods, risk of bias and funding not verified. The abstract does not break out the peppermint/menthol studies, their size or effect; the finding is described as preliminary with high risk of bias. Read: abstract
Madisch 1999 Treatment of functional dyspepsia with a fixed peppermint oil and caraway oil combination preparation as compared to cisapride. A multicenter, reference-controlled double-blind equivalence study. Arzneimittelforschung · PMID 10604046 · DOI	Controlled trial	120 Outpatients with functional dyspepsia (118 analysed)	Enteric-coated peppermint oil and caraway oil combination (Enteroplant) leaf (essential oil) plus caraway oil Peppermint oil 90 mg plus caraway oil 50 mg, one capsule twice daily 4 weeks · vs Cisapride 10 mg three times daily	Pain fell by 4.62 points with the combination and 4.60 with cisapride, shown to be equivalent. Both were well tolerated (adverse events in 12 vs 14 patients). Equivalent to cisapride on pain (p=0.021 for equivalence). Methods, limits and funding Outcomes: Pain score on a visual analogue scale Limitations: Compared with the drug cisapride rather than placebo; combination product, so peppermint oil alone is not tested. Read: abstract
Madisch 2004 Treatment of irritable bowel syndrome with herbal preparations: results of a double-blind, randomized, placebo-controlled, multi-centre trial. Aliment Pharmacol Ther · PMID 14984373 · DOI	Controlled trial	208 IBS patients, multicentre	STW 5 (nine plant extracts) or STW 5-II (six) or bitter candytuft alone mixed not in abstract 4 weeks · vs Placebo	STW 5 and STW 5-II beat placebo; candytuft alone did not STW 5 pain P=0.0009; symptoms P=0.001 Methods, limits and funding Outcomes: Abdominal pain and IBS symptom scores Limitations: The abstract does not list peppermint among the plants; check product composition before assuming it is included Read: abstract
Mahdavikian 2021 Comparing the Effect of Aromatherapy with Peppermint and Lavender Essential Oils on Fatigue of Cardiac Patients: A Randomized Controlled Trial. Evid Based Complement Alternat Med · PMID 34567223 · DOI	Controlled trial	105 Hospitalised cardiac patients	Peppermint or lavender essential oil, inhaled essential oil (aroma) 3 drops inhaled 7 nights · vs Aromatic placebo (3 drops)	Fatigue fell in the peppermint and lavender groups; both beat the placebo group (P<0.001) and did not differ from each other. Between-group P<0.001; no mean differences in the abstract (null) Methods, limits and funding Outcomes: Fatigue Severity Scale before and after Limitations: Abstract only; full methods, risk of bias and funding not verified. Self-rated fatigue; participants can smell the difference between oil and placebo; one hospital in Iran; not known if the change is large enough to matter. Funding and conflicts: Authors declare no conflicts of interest Read: abstract
Mascher 2001 Pharmacokinetics of menthol and carvone after administration of an enteric coated formulation containing peppermint oil and caraway oil. Arzneimittelforschung · PMID 11455677 · DOI	Controlled trial	16 16 healthy men	Enteric-coated peppermint and caraway oil capsules (2 capsules, 180 mg peppermint oil) versus immediate-release capsules (5 capsules) oil 180 mg peppermint oil Single dose, crossover · vs Immediate-release capsules	Total menthol exposure was equivalent (AUC 90% CI 97 to 105%). Peak menthol was 1196 ng/ml with enteric coating versus 1492 ng/ml with immediate release and arrived later (3.0 h versus 1.7 h). The paper states that enteric coating avoids discomfort caused by gastro-oesophageal reflux. Menthol AUC ratio 97-105% (90% CI 97-105%) Methods, limits and funding Outcomes: Menthol and carvone blood levels Limitations: Men only, single dose; the reflux statement is the authors' claim, not something this study measured. Funding and conflicts: Not stated in abstract Read: abstract
Masoumi 2016 Evaluation of mint efficacy regarding dysmenorrhea in comparison with mefenamic acid: A double blinded randomized crossover study. Iran J Nurs Midwifery Res · PMID 27563318 · DOI	Controlled trial	127 Female students with primary dysmenorrhoea, Hamadan	Peppermint extract capsules leaf (essential oil) 3 days per cycle, crossover · vs Mefenamic acid and placebo	Pain intensity and duration fell with both peppermint extract and mefenamic acid. Bleeding was lower with mefenamic acid. Nausea and diarrhoea were lower with peppermint. Pain and duration lower than placebo (P<0.05); bleeding not changed by peppermint. Methods, limits and funding Outcomes: Pain intensity (VAS), pain duration, blood loss Limitations: Self-reported; students only; extract details not in abstract; analgesic use higher in the peppermint group. Read: abstract
May 1996 Efficacy of a fixed peppermint oil/caraway oil combination in non-ulcer dyspepsia. Arzneimittelforschung · PMID 9006790	Controlled trial	45 Patients with non-ulcer dyspepsia (39 analysed)	Enteric-coated peppermint oil and caraway oil combination (Enteroplant) leaf (essential oil) plus caraway oil Peppermint oil 90 mg plus caraway oil 50 mg per capsule (schedule not stated in abstract) 4 weeks · vs Placebo	Pain and global impression were better than placebo after 4 weeks (p=0.015 and 0.008). 63.2% of the combination group were pain-free at the end. 7 adverse events (4 vs 3). Pain p=0.015; global impression p=0.008. Methods, limits and funding Outcomes: Pain intensity and Clinical Global Impression Limitations: Very small (19 vs 20 analysed); older trial; combination product. Read: abstract
May 2000 Efficacy and tolerability of a fixed combination of peppermint oil and caraway oil in patients suffering from functional dyspepsia. Aliment Pharmacol Ther · PMID 11121917 · DOI	Controlled trial	96 Outpatients with functional dyspepsia	Peppermint oil 90 mg + caraway oil 50 mg per enteric-coated capsule (Enteroplant) oil 1 capsule twice a day 28 days · vs Placebo	Pain -40% vs -22%; fullness -43% vs -22%; much or very much improved 67% vs 21% All three significant Methods, limits and funding Outcomes: Pain, fullness, global improvement Limitations: Small; 2000 Read: abstract
McConkey 2000 Developmental regulation of monoterpene biosynthesis in the glandular trichomes of peppermint. Plant Physiol · PMID 10631265 · DOI	Plant enzyme and gene expression study n/a	Peppermint leaves of different ages	n/a	Production is restricted to leaves 12-20 days old; enzyme activity peaks at about 15 days, except the last enzyme (menthone reductase) at about 21 days; regulation mainly at gene expression. Methods, limits and funding Outcomes: Time course of monoterpene production Limitations: Plant-biochemistry study. Read: abstract
McKay 2006 A review of the bioactivity and potential health benefits of peppermint tea (Mentha piperita L.). Phytother Res · PMID 16767798 · DOI	Narrative review mixed	Literature on peppermint tea and peppermint oil	Peppermint tea and oil leaf and oil varied varied · vs varied	Leaf phenolics include rosmarinic acid, eriocitrin, luteolin and hesperidin; oil is mainly menthol and menthone. In vitro: antimicrobial, antioxidant, some antiallergenic actions. Animal: gut relaxation, analgesia. Human studies cover the gut, airways and pain with the oil; human studies of leaf are limited and clinical trials of peppermint tea are absent. No adverse reactions to tea reported; caution with oil in reflux, hiatal hernia or kidney stones. Methods, limits and funding Outcomes: Bioactivity and potential health benefits Limitations: Narrative review (2006); not systematic; since 2006 more trials have appeared. Read: abstract
McKemy 2002 Identification of a cold receptor reveals a general role for TRP channels in thermosensation. Nature · PMID 11882888 · DOI	Cell cloning and receptor study animal	Mouse trigeminal neurons and cells expressing the channel	Menthol and cold	Cloned CMR1 (TRPM8), activated by menthol and by cool-to-cold temperatures. Methods, limits and funding Outcomes: Identity of the menthol receptor Limitations: Cell and animal work; not a clinical study. Read: abstract
Meamarbashi 2013 The effects of peppermint on exercise performance. J Int Soc Sports Nutr · PMID 23517650 · DOI	Other trial	12 Healthy male university students	Peppermint essential oil in water, swallowed essential oil (leaf, unspecified) 0.05 mL in 500 mL of mineral water, daily 10 days · vs Before-and-after comparison; no separate control group in the abstract	After 10 days, time to exhaustion rose from 664.5 +/- 114.2 s to 830.2 +/- 129.8 s (p<0.001), with higher lung-function and oxygen-use numbers. Time to exhaustion about +25% (derived from the two means as reported) Methods, limits and funding Outcomes: Spirometry, treadmill time to exhaustion (Bruce protocol), gas analysis, blood pressure and heart rate Limitations: Abstract only; full methods, risk of bias and funding not verified. Twelve people, apparently measured before and after with no placebo group (not stated clearly in the abstract), so training, learning and expectation could explain it; the authors' explanations (muscle relaxation, lactate) were not measured here. Read: abstract
Meamarbashi 2014 Instant effects of peppermint essential oil on the physiological parameters and exercise performance. Avicenna J Phytomed · PMID 25050303	Controlled trial	30 Healthy male university students	Peppermint essential oil, swallowed essential oil (leaf, unspecified) 50 microlitres, single dose Tests 5 minutes and 1 hour after dosing · vs Control group (15 vs 15)	The oil group improved on all measures versus control, e.g. grip force +36.1% and vertical jump +7.0%, with faster reaction times. Percent changes as reported; no CIs given (null) Methods, limits and funding Outcomes: Grip force, jumps, spirometry, reaction times, blood pressure, heart rate Limitations: Abstract only; full methods, risk of bias and funding not verified. Very large gains from one small dose are unusual and the later null studies in this file did not reproduce them; 30 students; the control was not described as a placebo in the abstract. Read: abstract
Melli 2007 A randomized trial of peppermint gel, lanolin ointment, and placebo gel to prevent nipple crack in primiparous breastfeeding women. Med Sci Monit · PMID 17767120	Controlled trial	216 First-time breastfeeding mothers	Peppermint gel leaf (essential oil) Applied after feeds (strength not stated in abstract) 14 days, follow-up at 6 weeks · vs Modified lanolin ointment or neutral gel	Fewer cracks with peppermint gel than lanolin or placebo gel (chi-square 16.8, P=0.01). Fewer nipple cracks versus both comparators. Methods, limits and funding Outcomes: Nipple and areola cracks, pain Limitations: The quoted relative risks as printed in the abstract are hard to interpret. Read: abstract
Melzer 2004 Meta-analysis: phytotherapy of functional dyspepsia with the herbal drug preparation STW 5 (Iberogast). Aliment Pharmacol Ther · PMID 15606389 · DOI	Meta-analysis	273 Functional dyspepsia; 3 placebo-controlled trials of STW 5	STW 5 (Iberogast; includes peppermint, chamomile, bitter candytuft) mixed not in abstract not in abstract · vs Placebo	Better than placebo; adverse events similar OR 0.22 (95% CI 0.11 to 0.47) Methods, limits and funding Outcomes: Most bothersome symptom Limitations: Analysis included producer-supplied data Read: abstract
Merat 2010 The effect of enteric-coated, delayed-release peppermint oil on irritable bowel syndrome. Dig Dis Sci · PMID 19507027 · DOI	Controlled trial	90 Outpatients with IBS, Tehran	Colpermin enteric-coated delayed-release peppermint oil unspecified 1 capsule three times a day (mg not in abstract) 8 weeks · vs Placebo	14 vs 6 free of pain or discomfort at week 8 P<0.001 Methods, limits and funding Outcomes: Pain-free numbers, pain severity, quality of life Limitations: Small Read: abstract
Meyer 2026 Systematic Review and Meta-Analysis: Plant-Based Therapy for Irritable Bowel Syndrome. Phytother Res · PMID 42572206 · DOI	Meta-analysis	6329 IBS; 60 studies of plant-based therapy	Fibre, peppermint oil, aloe vera, Chinese herbal medicine unspecified varied varied · vs Placebo	Peppermint oil (7 studies) RR 1.63; good safety profile RR 1.63 (95% CI 1.33 to 2.00) Methods, limits and funding Outcomes: Symptom improvement Limitations: Quality of many studies limited Funding and conflicts: No conflicts declared Read: abstract
Miranda Neto 2023 Peppermint essential oil (Mentha piperita L.) increases time to exhaustion in runners. Eur J Nutr · PMID 37665425 · DOI	Controlled trial	14 Recreational male runners	Peppermint essential oil in water, drunk essential oil (leaf, unspecified) 0.05 mL in 500 mL water before, plus 400 mL during the run Two runs to exhaustion at 70% of VO2max · vs Placebo drink (crossover)	Time to exhaustion 109.9 +/- 6.9 min with the oil versus 98.5 +/- 6.2 min with placebo (p=0.009; effect size 0.826). Perceived effort, body temperature, thermal sensation and comfort did not change. 11.4 min longer (derived from the two means); effect size 0.826 Methods, limits and funding Outcomes: Time to exhaustion; body temperature, heat sensation and comfort, perceived effort, sweat rate Limitations: Abstract only; full methods, risk of bias and funding not verified. Only 14 men; the runners did not feel the effort as easier even though they ran longer, so the mechanism is unknown; one trial. Registration: Brazilian Registry of Clinical Trials RBR-75zt25z Read: abstract
Mizuno 2006 Oral peppermint oil is a useful antispasmodic for double-contrast barium meal examination. J Gastroenterol Hepatol · PMID 16872313 · DOI	Controlled trial	420 Adults having double-contrast barium meal (stomach X-ray)	Peppermint oil taken by mouth with the barium leaf (essential oil) Dose not stated in abstract Single examination · vs Matched controls (205 peppermint vs 215 controls)	Less spasm in the oesophagus, lower stomach and duodenal bulb (P<0.001) and better diagnostic quality. No adverse effects in either group. Spasm scores lower (P<0.001). Methods, limits and funding Outcomes: Spasm and overlapping of barium loops, image quality Limitations: Controls were matched rather than clearly randomised; no placebo. Read: abstract
Morton 1995 Contact sensitivity to menthol and peppermint in patients with intra-oral symptoms. Contact Dermatitis · PMID 7634781 · DOI	Case series	12 Patients with burning mouth, recurrent mouth ulcers or lichenoid reaction, Glasgow Dental Hospital	Patch tests to menthol and peppermint oil oil Patch test 4 years referral period; mean follow-up 32.7 months	12 patients had contact sensitivity to menthol and/or peppermint oil. Of 9 patients reached at follow-up, 6 reported clearance or improvement after avoiding menthol and peppermint. Contact sensitivity in 12 referred patients Methods, limits and funding Outcomes: Contact sensitivity Limitations: Small referred sample with mouth symptoms; no denominator for how common this is. Read: abstract
Moss 2008 Modulation of cognitive performance and mood by aromas of peppermint and ylang-ylang. Int J Neurosci · PMID 18041606 · DOI	Controlled trial	144 Healthy volunteers	Peppermint aroma (inhaled) essential oil (aroma) Aroma exposure (amount not given in the abstract) During one testing session · vs Ylang-ylang aroma; no-aroma control	Peppermint enhanced memory (ylang-ylang impaired it) and raised self-rated alertness versus no aroma, with significant differences on several test factors. Significant differences between conditions; no effect sizes in the abstract (null) Methods, limits and funding Outcomes: Cognitive Drug Research computerised battery; mood scales before and after Limitations: Abstract only; full methods, risk of bias and funding not verified. Single session in healthy people; participants can often tell an aroma from no aroma, so expectation may play a role; no long-term or everyday-life outcome. Read: abstract
Mousavi Vahed 2022 Peppermint drop effect on ileus following cesarean section. J Family Med Prim Care · PMID 35516656 · DOI	Controlled trial	102 Women after Caesarean section	Mint drops leaf (essential oil) After surgery until first stool · vs Placebo drops	First bowel sounds at 5.78 h vs 9.05 h; first gas at 7.87 h vs 12.24 h. No nausea or vomiting in either group. Faster return of bowel function. Methods, limits and funding Outcomes: Time to first bowel sound, first gas, first stool, hospital stay Limitations: The abstract says 'mint' and does not name peppermint; small; setting not detailed. Read: abstract
National Center for Complementary and Integrative Health (NIH) 2025 Peppermint Oil (NCCIH Herbs at a Glance) NCCIH web page (last updated May 2025) · Source	Authoritative guidance		Peppermint oil aerial parts essential oil	Page read through an automated summarising tool, not word for word. Says peppermint oil appears safe by mouth or on the skin at commonly used doses; oral side effects include heartburn, nausea, abdominal pain and dry mouth; allergic reactions are rare; skin use can cause rashes and irritation; capsules are often enteric-coated to reduce heartburn risk; do not apply to the face of infants or young children because menthol can cause serious harm if they inhale it; food amounts likely safe in pregnancy and breastfeeding, medicinal amounts not well studied; if breastfeeding and using on skin, use after nursing and wipe off before the next feeding. The page lists no specific interactions. Methods, limits and funding Limitations: Consumer fact sheet; no figures. Retrieved through a summariser, so exact wording was not checked. Read: summary-only
Nee 2021 Peppermint Oil Treatment for Irritable Bowel Syndrome: A Randomized Placebo-Controlled Trial. Am J Gastroenterol · PMID 34319275 · DOI	Controlled trial	Adults with IBS (Rome IV) and moderate to severe symptoms, one US centre	Enteric-coated peppermint oil leaf (essential oil) 180 mg three times daily 6 weeks · vs Placebo (randomised 1:2)	Both groups improved a lot. Improvement was 90.8 points (SD 75.3) with peppermint oil and 100.3 (SD 99.6) with placebo; the difference was not significant (P=0.97) and no secondary measure differed. Effect size d = -0.11 (peppermint oil numerically slightly worse than placebo). Methods, limits and funding Outcomes: Change in IBS Severity Scoring System score Limitations: Single centre; short; sample size not given in the abstract. Read: abstract
Nishi 2025 Heterogeneity in the Study of Peppermint in Aromatherapy on Cognition and Attention: A Critical Scoping Review. Complement Med Res · PMID 40031879 · DOI	Systematic review	Human studies of inhaled peppermint and cognition (8 selected from 115 found)	Inhaled peppermint scent essential oil (aroma) Various Various · vs Various	Eight studies met the criteria and were quite different from each other in design and measures. The authors conclude that a definitive conclusion is premature and that more carefully designed studies are needed. None (scoping review) Methods, limits and funding Outcomes: Cognition and attention Limitations: Abstract only; full methods, risk of bias and funding not verified. A scoping review does not pool results or grade them; it summarises how varied the studies are. Read: abstract
Nolen HW 3rd 1994 Menthol-beta-D-glucuronide: a potential prodrug for treatment of the irritable bowel syndrome. Pharm Res · PMID 7899232 · DOI	Laboratory stability study in-vitro	Rat gut contents; human stool samples	Menthol-beta-D-glucuronide 4-24 hours	Stable at pH 4.5-7.4; about 20% hydrolysed in 4 h at pH 1.5; hydrolysed in rat caecum/colon and more slowly in human stool; poor lumen absorption predicted. Methods, limits and funding Outcomes: Stability and hydrolysis Limitations: Rat and stool in-vitro work on a prodrug idea. Read: abstract
Norrish 2005 Preliminary investigation of the effect of peppermint oil on an objective measure of daytime sleepiness. Int J Psychophysiol · PMID 15708642 · DOI	Controlled trial	Adult volunteers (number not given in the abstract)	Peppermint oil aroma essential oil (aroma) Not given in the abstract 11 minutes in a darkened room · vs No-odour condition	With peppermint oil the rise in sleepiness during 11 minutes in a darkened room was limited versus no odour, unrelated to starting self-rated sleepiness. Significant difference reported; numbers not in the abstract (null) Methods, limits and funding Outcomes: Pupillary fatigue oscillations (an objective index of sleepiness) and the Stanford Sleepiness Scale Limitations: Abstract only; full methods, risk of bias and funding not verified. Preliminary, short, in a room designed to induce sleepiness; the authors say applicability to real life needs further work. Read: abstract
Olowe 1980 The risk of jaundice in glucose-6-phosphate dehydrogenase deficient babies exposed to menthol. Acta Paediatr Scand · PMID 7376859 · DOI	Non randomised trial	60 G6PD-deficient newborns in Lagos, Nigeria	Mentholated powder on the umbilical cord menthol-containing powder Daily dressing · vs 30 untreated babies	The 30 babies with mentholated powder on the cord developed significantly more jaundice than the 30 untreated G6PD-deficient controls. The authors conclude menthol- and camphor-containing products on newborns should be discontinued, especially where G6PD deficiency is common. Methods, limits and funding Outcomes: Neonatal jaundice Limitations: Newborns, skin powder on the cord, product contained menthol (camphor also mentioned); not peppermint oil or tea in older people. Abstract does not give numbers. Read: abstract
Parvizi 2025 The effect of peppermint essential oil on postoperative nausea, vomiting, and pain in rhinoplasty patients: a randomized clinical trial. Ann Med Surg (Lond) · PMID 40337441 · DOI	Controlled trial	80 Adults having rhinoplasty	Oral peppermint essence leaf (essential oil) 20 oral drops of 2% peppermint essence, 30 min before surgery Single dose · vs Distilled water	Less nausea at all three time points (P<0.001). No significant difference in vomiting or pain. Lower nausea; no vomiting or pain effect. Methods, limits and funding Outcomes: Postoperative nausea, vomiting and pain (VAS) Limitations: Small; swallowing essential oil is not a standard preparation. Read: abstract
Pasha 2012 Study of the effect of mint oil on nausea and vomiting during pregnancy. Iran Red Crescent Med J · PMID 23396673 · DOI	Controlled trial	60 Pregnant women with nausea and vomiting	Peppermint essential oil in a bowl of water by the bed leaf (essential oil) 4 drops, four nights 4 nights · vs Saline	No significant difference between groups for nausea or vomiting. Nausea trended down in the peppermint group by the fourth night, not significant. No effect. Methods, limits and funding Outcomes: Nausea (VAS) and vomiting counts Limitations: Small; short; passive exposure by the bed. Read: abstract
Peier 2002 A TRP channel that senses cold stimuli and menthol. Cell · PMID 11893340 · DOI	Cell cloning and receptor study in-vitro	Cells overexpressing TRPM8; mouse sensory neurons	Menthol and cold	TRPM8 is expressed in a subset of pain- and temperature-sensing neurons and is activated by cold and by menthol. Methods, limits and funding Outcomes: Cold and menthol sensing by TRPM8 Limitations: Cell work. Read: abstract
Pimentel 2001 Peppermint oil improves the manometric findings in diffuse esophageal spasm. J Clin Gastroenterol · PMID 11418786 · DOI	Case series	8 Patients with diffuse oesophageal spasm found at diagnostic manometry	Peppermint oil in water leaf (essential oil) 5 drops in 10 mL water, single dose Measured 10 minutes after the drink · vs Before-and-after in the same patients (no control group)	Simultaneous contractions disappeared in all 8 patients (p<0.01). Resting sphincter pressure did not change. 2 of 8 had chest pain that went away. Simultaneous contractions eliminated (p<0.01). Methods, limits and funding Outcomes: Oesophageal pressure waves; chest pain Limitations: Eight patients, no placebo, single dose, measured only minutes later. Read: abstract
Portincasa 2016 Curcumin and Fennel Essential Oil Improve Symptoms and Quality of Life in Patients with Irritable Bowel Syndrome. J Gastrointestin Liver Dis · PMID 27308645 · DOI	Controlled trial	121 Mild to moderate IBS	Curcumin plus fennel essential oil oil 2 capsules twice a day 30 days · vs Placebo	50.05% vs 26.12% fall; symptom-free 25.9% vs 6.8% P<0.001 Methods, limits and funding Outcomes: IBS-SSS Limitations: Combination; cannot credit fennel alone Read: abstract
Pournemati 2009 The effect of inhaling peppermint odor and ethanol in women athletes. Bratisl Lek Listy · PMID 20196473	Controlled trial	36 Women soccer players	Inhaled peppermint odour, or peppermint plus ethanol essential oil (aroma) Inhaled before a treadmill test One acute treadmill test (Bruce protocol) · vs Control group (3 groups of 12)	No significant effect on running time, heart rate, VO2max, ventilation or respiratory exchange ratio. No effect Methods, limits and funding Outcomes: Running time, heart rate, VO2max, minute ventilation Limitations: Abstract only; full methods, risk of bias and funding not verified. Group split inferred from 36 players in 3 groups; a single hard test. Read: abstract
Rafieian-Kopaei 2019 Comparing the Effect of Intranasal Lidocaine 4% with Peppermint Essential Oil Drop 1.5% on Migraine Attacks: A Double-Blind Clinical Trial. Int J Prev Med · PMID 31404204 · DOI	Controlled trial	120 Adults with migraine (IHS criteria)	Peppermint essential oil drops 1.5%, intranasal essential oil Nasal drops, a second dose after 15 minutes if the headache persisted Single migraine attack, follow-up by phone and in person at 2 months · vs Intranasal lidocaine 4%; placebo	Headache intensity differed between groups after treatment (P<0.001). About 40% of the peppermint and lidocaine patients had a decrease in intensity; the placebo group had fewer high responders. About 42% (peppermint) and 41.5% (lidocaine) responded considerably. The authors conclude peppermint nasal drops cut intensity and frequency of headache about as well as lidocaine. Group differences P<0.001; no effect sizes in the abstract (null) Methods, limits and funding Outcomes: Headache intensity at 5, 15 and 30 minutes; follow-up questionnaires Limitations: Abstract only; full methods, risk of bias and funding not verified. The abstract is unclear about exact group sizes, responder definition and the placebo result; all pain outcomes were self-reported; nasal drops of essential oil are not a standard or regulated product, so this does not apply to oil you buy; not replicated. Funding and conflicts: Authors declare no conflicts of interest Read: abstract
Reinhard 2021 Pyrrolizidine alkaloids in tea, herbal tea and iced tea beverages- survey and transfer rates. Food Addit Contam Part A Chem Anal Control Expo Risk Assess · PMID 34237234 · DOI	Other in-vitro	10 Ten naturally contaminated teas and herbal teas, including peppermint tea, and 46 iced teas	Pyrrolizidine alkaloid testing leaf	Total pyrrolizidine alkaloids ranged 154 to 2412 ng/g in the ten herbs (median 422); 38 to 100% (median 95%) passed into the brew. The abstract does not separate out the peppermint sample, so no peppermint-specific figure is given. 154-2412 ng/g across ten teas Methods, limits and funding Outcomes: Pyrrolizidine alkaloid content Limitations: Samples were chosen because they were contaminated; says nothing about how common contamination is. Read: abstract
Rich 2017 A randomized placebo-controlled trial on the effects of Menthacarin, a proprietary peppermint- and caraway-oil-preparation, on symptoms and quality of life in patients with functional dyspepsia. Neurogastroenterol Motil · PMID 28695660 · DOI	Controlled trial	114 Outpatients with chronic or recurrent functional dyspepsia	Menthacarin (peppermint oil + caraway oil) leaf (essential oil) plus caraway oil One capsule twice daily 4 weeks · vs Placebo	After 4 weeks pain improved by 7.6 points with the combination and 3.4 with placebo; discomfort by 3.6 and 1.3. All secondary measures favoured the combination. Pain: -7.6 (SD 4.8) vs -3.4 (SD 4.3). Discomfort: -3.6 (SD 2.5) vs -1.3 (SD 2.1). Methods, limits and funding Outcomes: Nepean Dyspepsia Index pain and discomfort scores Limitations: Combination product; short; manufacturer-linked product (funding not stated in abstract). Read: abstract
Rites 2024 Effects of peppermint oil inhalation on vertical jump performance in elite young professional soccer players: A double-blinded randomized crossover study. Heliyon · PMID 38293549 · DOI	Controlled trial	11 Under-17 professional soccer players	Peppermint essential oil, inhaled essential oil (aroma) Inhaled 10 minutes before retesting Single session · vs Placebo (crossover)	Countermovement jump fell in both conditions with the fall smaller (by effect size) with peppermint; no effect for squat jump. The authors suggest it might limit the drop in performance after rest. Main effect of time on jump height p=0.037; no peppermint-specific test reported in the abstract Methods, limits and funding Outcomes: Squat jump and countermovement jump height Limitations: Abstract only; full methods, risk of bias and funding not verified. Eleven players; the abstract's main finding is that both conditions lost jump height, and a difference between them is only a trend in effect size; not a clear benefit. Funding and conflicts: Authors declare no competing interests Read: abstract
Safajou 2020 The Effect of Combined Inhalation Aromatherapy with Lemon and Peppermint on Nausea and Vomiting of Pregnancy: A Double-Blind, Randomized Clinical Trial. Iran J Nurs Midwifery Res · PMID 33344211 · DOI	Controlled trial	90 Pregnant women with nausea and vomiting, Iran	Inhaled lemon and peppermint oils together leaf (essential oil) plus lemon oil 3 drops on a cotton ball held 3 cm from the nose 4 days · vs Placebo	Scores differed between groups from day 2 and fell over time only in the aromatherapy group (F=22.92, p<0.001). Lower nausea and vomiting scores from day 2. Methods, limits and funding Outcomes: PUQE-24 score Limitations: Mixed oils; mild to moderate cases; short. Read: abstract
Sant'Ambrogio 1992 Menthol in the upper airway depresses ventilation in newborn dogs. Respir Physiol · PMID 1410843 · DOI	Animal research animal	8 Anaesthetised newborn dogs (7 to 14 days old)	l-menthol in warm air through the upper airway menthol Constant airflow with menthol Experimental trials	Warm air with l-menthol cut ventilation to 52.8% of control (cold air alone 57.5%), mostly by lengthening the breath cycle; part of the menthol effect was removed by nasal anaesthesia. Ventilation to 52.8% of control Methods, limits and funding Outcomes: Breathing Limitations: Animal study; supports a plausible reflex, not a measure of human infant risk. Read: abstract
Sayyah Melli 2007 Effect of peppermint water on prevention of nipple cracks in lactating primiparous women: a randomized controlled trial. Int Breastfeed J · PMID 17442122 · DOI	Controlled trial	196 First-time breastfeeding mothers, Tabriz, Iran	Peppermint water leaf (essential oil) Applied daily Up to 14 days, follow-up at 6 weeks · vs Expressed breast milk	Nipple and areola cracks 9% vs 27% (P<0.01). Nipple pain lower with peppermint water (OR 5.6, 95% CI 2.2-14.6). Cracks 9% vs 27%. (Pain OR 2.2-14.6) Methods, limits and funding Outcomes: Nipple cracks, nipple pain Limitations: Comparator was expressed milk rather than placebo; not blinded. Read: abstract
Shah 2019 Peppermint Oil to Improve Visualization in Screening Colonoscopy: A Randomized Controlled Clinical Trial. Gastroenterology Res · PMID 31236155 · DOI	Controlled trial	48 Adults having screening colonoscopy	Peppermint oil injected through the colonoscope leaf (essential oil) 50 mL injected through the working channel once the caecum was reached Single dose · vs Placebo	Complete absence of spasm: 58.3% vs 45.8% (P=0.05). Time to reach the caecum: 7.2 vs 10.3 min (P=0.04). Adenoma detection 45.8% vs 37.5% (P=0.56, not significant). Less spasm and faster caecum intubation; adenoma difference not significant. Methods, limits and funding Outcomes: Colonic spasm, peristalsis, bowel visibility, procedure time, adenoma detection rate Limitations: Small (24 vs 24); the spasm result is borderline; adenoma rate not powered. Read: abstract
Shanazi 2015 Comparison of the Effects of Lanolin, Peppermint, and Dexpanthenol Creams on Treatment of Traumatic Nipples in Breastfeeding Mothers. J Caring Sci · PMID 26744729 · DOI	Controlled trial	126 Breastfeeding mothers with traumatic nipples, Sanandaj	Peppermint cream leaf (essential oil) 14 days · vs Lanolin cream or dexpanthenol cream	No difference between peppermint, lanolin and dexpanthenol; all improved over time. Similar effects. Methods, limits and funding Outcomes: Nipple pain and trauma Limitations: No placebo arm, so the healing could be natural. Read: abstract
Sharafi 2026 The Impact of Peppermint Oil Aromatherapy on Hemodynamic Parameters, Anxiety, and Stress in Patients With Acute Coronary Syndrome: A Randomized Clinical Trial. Glob Adv Integr Med Health · PMID 42253765 · DOI	Controlled trial	Patients with acute coronary syndrome in hospitals in Qom, Iran	Peppermint essential oil on an eye pad essential oil (aroma) 0.2 mL on an eye pad One 20-minute session · vs Normal saline on an eye pad	Versus placebo: anxiety fell from 24.64 +/- 5.15 to 19.55 +/- 3.10 and stress from 25.00 +/- 5.14 to 17.18 +/- 4.42 (P<0.001); systolic pressure fell from 139.77 to 126.36 mmHg, also with lower diastolic pressure, heart rate and pain. Anxiety and stress P<0.001 (before/after means as stated) Methods, limits and funding Outcomes: Anxiety and stress scores, blood pressure, heart rate, pain scores Limitations: Abstract only; full methods, risk of bias and funding not verified. Sample size not stated in the abstract; the figures shown are before/after values in the oil group; the test scales are not named in the abstract; a single short session during a heart emergency stay; the size of the blood-pressure drop looks very large and replication is needed. Funding and conflicts: Authors declare no competing interests Read: abstract
Shavakhi 2012 Premedication with peppermint oil capsules in colonoscopy: a double blind placebo-controlled randomized trial study. Acta Gastroenterol Belg · PMID 23082707	Controlled trial	65 Adults having elective colonoscopy	Enteric-coated peppermint oil capsules (Colpermin) by mouth leaf (essential oil) Capsules 4 hours before the procedure (dose not stated in abstract) Single pre-procedure dose · vs Placebo capsules	Caecal and total procedure times were shorter; spasm and pain scores lower; endoscopist satisfaction higher; patients more willing to repeat colonoscopy. Significant benefits on all listed outcomes; numbers not given in the abstract. Methods, limits and funding Outcomes: Caecal intubation time, total time, spasm score, pain score, satisfaction Limitations: Numbers not in abstract; a later trial using the same product found no benefit. Read: abstract
Shepherd 2017 Aerobic capacity is not improved following 10-day supplementation with peppermint essential oil. Appl Physiol Nutr Metab · PMID 28177705 · DOI	Controlled trial	7 Healthy participants	Peppermint essential oil, swallowed essential oil (leaf, unspecified) Dose not given in the abstract 10 days · vs Control (randomised crossover)	No difference: peak oxygen uptake 3.54 vs 3.52 L/min; time to exhaustion 583.33 vs 587.04 s. No effect Methods, limits and funding Outcomes: Graded maximal exercise test: peak oxygen uptake, time to exhaustion Limitations: Abstract only; full methods, risk of bias and funding not verified. Only 7 people; the dose is not in the abstract. Read: abstract
Shetty 2024 Effectiveness of the Application of Lanolin, Aloe Vera, and Peppermint on Nipple Pain and Nipple Trauma in Lactating Mothers: A Systematic Review and Meta-Analysis. Matern Child Health J · PMID 39436586 · DOI	Meta-analysis	1495 Breastfeeding mothers (11 studies; lanolin, aloe vera and peppermint)	Peppermint applied to nipples (with lanolin and aloe vera reviewed) leaf (essential oil) Varied Varied · vs Varied	Peppermint reduced nipple trauma (cracks); lanolin reduced both pain and trauma. Peppermint's effect on pain is not stated as significant in the abstract. Nipple trauma reduced with peppermint; no figures in abstract. Methods, limits and funding Outcomes: Nipple pain and nipple trauma Limitations: Pooled trials of different preparations; numbers not in abstract. Registration: PROSPERO CRD42023407225 Read: abstract
Shulman 2022 Randomised trial: Peppermint oil (menthol) pharmacokinetics in children and effects on gut motility in children with functional abdominal pain. Br J Clin Pharmacol · PMID 34528282 · DOI	Randomised dose ranging pharmacokinetic study	30 Children aged 7-12 with functional abdominal pain	Enteric-coated peppermint oil oil 180, 360 or 540 mg single dose then 1 week · vs between dose groups	Menthol exposure rose in line with dose; mean half-life 2.1, 3.5 and 4.6 hours; colonic transit time fell with greater exposure; stomach, small-bowel and whole-gut contractility rose with exposure. Methods, limits and funding Outcomes: Menthol exposure and gut motility Limitations: Small groups of 10; motility data incomplete; an erratum exists for this paper. Funding and conflicts: Authors report no conflicts to declare (from the paper's statement). Registration: NCT03295747 Read: abstract
Sokolov 2024 Menthol dural application alters meningeal arteries tone and enhances excitability of trigeminocervical neurons in rats. Brain Res · PMID 38128811 · DOI	Animal research animal	Male rats (acute experiments)	Menthol solution (1%, 5%, 10%, 30%) applied directly to the dura menthol (isolated compound) 1% to 30% solutions applied to the brain's outer covering Acute experiment · vs Control	5% and 10% menthol reduced the vessel-dilation response by tightening vessels; 1% and 30% intensified responses of pain-signalling neurons to stimulation. The authors read this as menthol receptor (TRPM8) activation being pro-headache and suggest looking for TRPM8 blockers. Not applicable (animal) Methods, limits and funding Outcomes: Dural blood vessel dilation and trigeminocervical neuron firing Limitations: Abstract only; full methods, risk of bias and funding not verified. Rat experiment with menthol placed directly on the dura, which does not happen with skin or nose use in people; the mechanism evidence cuts both ways (cooling vs. pain-signalling). Read: abstract
Sparks 1995 Does peppermint oil relieve spasm during barium enema? Br J Radiol · PMID 7551780 · DOI	Controlled trial	141 Patients having double-contrast barium enema	Peppermint oil added to the barium suspension leaf (essential oil) Single examination · vs Standard barium suspension	No residual spasm in 60% of the peppermint group vs 35% of controls (p<0.001). Patients accepted the procedure and image quality was not harmed; no adverse effects. 60% vs 35% spasm-free (p<0.001). Methods, limits and funding Outcomes: Residual colonic spasm on films Limitations: Older trial; dose not given in the abstract; no placebo oil. Read: abstract
St Cyr 2015 Efficacy and Tolerability of STOPAIN for a Migraine Attack. Front Neurol · PMID 25699012 · DOI	Single arm trial	25 Adults with episodic migraine (32 enrolled, 25 completed)	Menthol 6% gel (STOPAIN), not peppermint oil menthol (isolated compound) Gel applied to the skull base within 2 hours of onset Single migraine attack, 2-hour check plus 24-hour follow-up · vs No comparator (open-label)	Two hours later 28% had no pain, 28% mild, 25% moderate, 20% severe (percentages as in the abstract). Most had similar pain (32%) or improvement (52%). 12 of 25 took rescue medicine before 24 hours. Authors report a 'significant improvement' by 2 hours; no p-value in the abstract (null) Methods, limits and funding Outcomes: Pain severity before and 2 hours after gel Limitations: Abstract only; full methods, risk of bias and funding not verified. Open-label pilot with no placebo group and no blinding; 7 of 32 enrolled did not finish; migraine pain often fades by itself and responds strongly to placebo, so this cannot show the gel works. Menthol gel, not peppermint oil. Read: abstract
Suen 2026 High-Intensity Intermittent Exercise and Mouth Rinsing: A Systematic Review and Meta-Analysis. Int J Sport Nutr Exerc Metab · PMID 41791366 · DOI	Meta-analysis	People doing high-intensity intermittent exercise (20 randomised crossover studies)	Carbohydrate, caffeine and/or menthol mouth rinses menthol (isolated compound) Various Various · vs Placebo rinse	No significant improvement for carbohydrate, caffeine or combined rinses. For menthol the review reports no performance benefit in hot conditions despite a better cooling sensation. No benefit for menthol on performance; cooling feel improved Methods, limits and funding Outcomes: High-intensity intermittent performance: power, distance, sprint time Limitations: Abstract only; full methods, risk of bias and funding not verified. Menthol results are described briefly with no numbers in the abstract; mouth rinse only. Read: abstract
Sullivan 1998 Effects of olfactory stimulation on the vigilance performance of individuals with brain injury. J Clin Exp Neuropsychol · PMID 9777477 · DOI	Controlled trial	People with brain injury and healthy controls	Peppermint scent puffs essential oil (aroma) Periodic whiffs during the task One vigilance session · vs Unscented air	In people with brain injury false alarms rose steeply late in the task with plain air; with peppermint scent their false-alarm scores resembled the controls'. Direction only (null) Methods, limits and funding Outcomes: False alarms during a long vigilance task Limitations: Abstract only; full methods, risk of bias and funding not verified. Small, old, laboratory attention test; sample size not given in the abstract; it concerned false alarms, not overall alertness. Read: abstract
Sullivan JB Jr 1979 Pennyroyal oil poisoning and hepatotoxicity. JAMA · PMID 513258	Case series	Pennyroyal oil poisoning	Pennyroyal oil oil	Title read only: JAMA report of pennyroyal oil poisoning and liver toxicity. The abstract is not available on PubMed, so no details are claimed. Methods, limits and funding Outcomes: Liver toxicity Limitations: Title only; not peppermint. Read: summary-only
Tang 2026 Effect of inhaled peppermint essential oil aromatherapy on postoperative nausea and vomiting in patients undergoing laparoscopic gynecologic surgery. Explore (NY) · PMID 41544308 · DOI	Controlled trial	106 Women having laparoscopic gynaecologic surgery	Inhaled 2% peppermint essential oil leaf (essential oil) Inhaled before induction, before surgery and after extubation Around surgery · vs Saline inhalation	PONV in 52.8% vs 73.6% (P=0.043); first hour 45.3% vs 73.6% (P=0.047). Anxiety, pain catastrophising and abdominal distension also improved. PONV 52.8% vs 73.6%. Methods, limits and funding Outcomes: Postoperative nausea and vomiting within 24 hours Limitations: Borderline P values; aroma may reveal the allocation. Registration: ChiCTR2400093289 Read: abstract
Tate 1997 Peppermint oil: a treatment for postoperative nausea. J Adv Nurs · PMID 9378876 · DOI	Controlled trial	Gynaecological surgery patients	Peppermint oil leaf (essential oil) Day of operation · vs Placebo and no-treatment groups	The peppermint group had less nausea than placebo on the day of surgery (P=0.02). They also needed fewer standard antiemetics and received more opioid pain relief. Kruskal-Wallis P=0.0487; placebo vs peppermint P=0.02. Methods, limits and funding Outcomes: Postoperative nausea, antiemetic use Limitations: Older, small; sample size not in the abstract; more opioid use may be a confounder. Read: abstract
Thomassen 1990 Menthofuran-dependent and independent aspects of pulegone hepatotoxicity: roles of glutathione. J Pharmacol Exp Ther · PMID 2338648	Rat toxicology study animal	Rats	Pulegone, menthofuran	Pulegone depleted liver and plasma glutathione and its toxicity was enhanced by blocking glutathione synthesis; two bioactivation routes were proposed. Methods, limits and funding Outcomes: Liver toxicity and glutathione Limitations: Rat study at toxic doses. Read: abstract
Thomassen 1992 Reactive intermediates in the oxidation of menthofuran by cytochromes P-450. Chem Res Toxicol · PMID 1581528 · DOI	Laboratory toxicology study animal	Rodents and liver preparations	Menthofuran	Liver damage was linked to P450 activation and covalent binding to proteins; a gamma-ketoenal was the main electrophile. Methods, limits and funding Outcomes: Reactive metabolites Limitations: Preclinical. Read: abstract
Thorup 1983 Short term toxicity study in rats dosed with pulegone and menthol. Toxicol Lett · PMID 6658833 · DOI	Animal research animal	Rats	Pulegone and menthol by stomach tube pure compounds Pulegone 0, 20, 80, 160 mg/kg a day; menthol 0, 200, 400, 800 mg/kg a day 28 days	At the two highest pulegone doses rats had atonia, lower blood creatinine, lower body weight and changes in the liver and in cerebellar white matter. Menthol at all doses raised liver weight and caused vacuolisation of liver cells; no encephalopathy. No-effect level was 20 mg/kg a day for pulegone and below 200 mg/kg a day for menthol. NOAEL pulegone 20 mg/kg/day Methods, limits and funding Outcomes: Liver, brain, kidney findings Limitations: Rats; very high doses compared with peppermint oil use. Read: abstract
Toniolo 2021 Effectiveness of Inhaled Aromatherapy on Chemotherapy-Induced Nausea and Vomiting: A Systematic Review. J Altern Complement Med · PMID 34283916 · DOI	Systematic review	People with cancer having chemotherapy (11 studies: 9 adult, 2 children)	Inhaled aromatherapy (peppermint, ginger, chamomile, cardamom) leaf (essential oil) Varied Varied · vs Standard care	Seven of nine adult studies showed significant results. Four of seven relieved both nausea and vomiting with peppermint or ginger oil. Diffusing the oil into the room and the two paediatric studies showed no benefit. No pooled effect size. Methods, limits and funding Outcomes: Chemotherapy-induced nausea and vomiting Limitations: Mostly women with gynaecological cancers; small samples; many different oils and methods. Read: abstract
Varney 2013 Effect of inhaled essential oils on mental exhaustion and moderate burnout: a small pilot study. J Altern Complement Med · PMID 23140115 · DOI	Controlled trial	14 13 women and 1 man with self-rated mental exhaustion or moderate burnout	Blend of peppermint, basil and helichrysum oils (personal inhaler) essential oil blend (aroma) Personal inhaler, 3 times a day on weekdays 1 week of treatment after 1 week of baseline · vs Inhaler with rose water	Both groups reported less burnout; the aroma group had a much greater reduction. Not given as numbers in the abstract (null) Methods, limits and funding Outcomes: Self-rated burnout on a 0-10 scale Limitations: Abstract only; full methods, risk of bias and funding not verified. Only 14 people; a three-oil blend, so peppermint alone cannot be separated out; self-rated; a pilot. Read: abstract
Vermeijden 2026 Peppermint Oil and Sweets in Pediatric Irritable Bowel Syndrome and Functional Abdominal Pain: A Randomized Trial. Clin Gastroenterol Hepatol · PMID 41610933 · DOI	Controlled trial	228 Children aged 8-18 with IBS or functional abdominal pain, 13 Dutch hospitals	Peppermint oil capsules or peppermint sweets leaf (essential oil) Capsules: 182 mg peppermint oil twice daily (8-11 years) or three times daily (12-18); sweets: 9.2 mg peppermint oil 8 weeks, plus 4 weeks follow-up · vs Placebo (2.0 mg peppermint oil to help blinding)	Treatment success: 44.0% peppermint oil, 37.3% placebo, 38.7% sweets. Adequate relief: 53.3%, 49.3%, 44.9%. Neither peppermint oil nor sweets beat placebo. Adverse events mild and infrequent. Peppermint oil vs placebo for treatment success: OR 1.33; adequate relief: OR 1.15. (Success OR 97.5% CI 0.58-3.09; relief OR 0.54-2.47) Methods, limits and funding Outcomes: Treatment success (30% or more drop in pain) and adequate relief Limitations: Sweets arm was open-label; findings apply to this age group and preparation. Registration: ClinicalTrials.gov NCT05799053 Read: abstract
Vogel 2023 A Menthol-Enhanced "Cooling" Energy Gel Does Not Influence Laboratory Time Trial Performance in Trained Runners. Nutrients · PMID 37571316 · DOI	Controlled trial	14 Trained runners (6 female)	Menthol 0.5% energy gel, swallowed (not peppermint oil) menthol (isolated compound) Taken 5 minutes before and at 20 and 40 minutes of the run 40-minute run at 33 C then a 20-minute time trial · vs Flavour-matched placebo gel (crossover)	No difference in distance (4.22 km each; p=0.867) or in any perception measure, including perceived exertion; thinking tests also unchanged. No difference Methods, limits and funding Outcomes: Distance in the 20-minute time trial; thermal comfort, sensation, perceived exertion, mood, thinking tests Limitations: Abstract only; full methods, risk of bias and funding not verified. 14 runners in a lab at 33 C; one author works for the gel company, which did not influence the design per the stated COI. Funding and conflicts: One author is an employee of GU Energy Labs, which had no role in design, data or publication according to the authors Read: abstract
Wacher 2002 Peppermint oil enhances cyclosporine oral bioavailability in rats: comparison with D-alpha-tocopheryl poly(ethylene glycol 1000) succinate (TPGS) and ketoconazole. J Pharm Sci · PMID 11782899 · DOI	Animal research animal	Male Sprague-Dawley rats	Peppermint oil with cyclosporine 25 mg/kg oil 100 mg/kg Single dose	Peppermint oil tripled cyclosporine peak concentration (0.60 to 1.6 ug/ml) and raised AUC from 8.3 to 24.3 ug h/ml; the time to peak went from 2 to 6 h. Ketoconazole had no effect, suggesting CYP3A inhibition is not the only route. AUC about 2.9 times Methods, limits and funding Outcomes: Cyclosporine absorption Limitations: Rats; the dose per kg is high compared with a capsule; no human data. Read: abstract
Wang 2024 Aromatherapy for the prevention of postoperative nausea and vomiting: A systematic review and meta-analysis. Tzu Chi Med J · PMID 38993833 · DOI	Meta-analysis	Adults having surgery (8 randomised trials in the meta-analysis; many oils)	Aromatherapy including peppermint, ginger and lavender oils (inhaled) leaf (essential oil) Varied Varied · vs Placebo or no aromatherapy	Aromatherapy reduced postoperative nausea severity but the drop in vomiting was not significant. Subgroup analysis suggested ginger, lavender and peppermint were effective. Certainty low (GRADE). Nausea SMD -0.93; vomiting SMD -0.81 (not significant). (Nausea -1.64 to -0.22; vomiting -1.98 to 0.37) Methods, limits and funding Outcomes: Postoperative nausea severity, vomiting episodes Limitations: High heterogeneity; mixed oils; low certainty. Read: abstract
Wang 2024 Comprehensive quality assessment of peppermint oils and commercial products: An integrated approach involving conventional and chiral GC/MS coupled with chemometrics. J Chromatogr B Analyt Technol Biomed Life Sci · PMID 38101286 · DOI	Other in-vitro	58 22 authentic peppermint oils and 36 commercial products labelled as containing peppermint oil	Gas chromatography of peppermint oil terpenoids oil · vs ISO specification and authentic oils	53% of the selected commercial products did not meet ISO specifications; the menthone/isomenthone ratio was a useful marker of adulteration; the enantiomer pattern of 27 commercial products was outside the range of authentic oils, and only eight of those 27 met the ISO standard. 53% failed ISO specification Methods, limits and funding Outcomes: Authenticity Limitations: Selected products, US market; this does not say how many sold as capsules are affected. Read: abstract
Warshaw 2025 Patch Testing to Mentha piperita (Peppermint) Oil: The North American Contact Dermatitis Group Experience (2009-2020). Dermatitis · PMID 39172635 · DOI	Retrospective cohort	28128 Patients patch tested for suspected contact dermatitis, North America 2009-2020	Peppermint oil 2% in petrolatum (patch test) oil 2% in petrolatum Patch test	161 of 28,128 patch-tested patients (0.6%) had an allergic reaction; 77.0% were women, 71.4% over 40; sites mostly face (31.7%, a third on the lips), hands (17.4%) and scattered/generalised (18.6%); 30.4% of reactions strong or extreme; 80.1% judged currently relevant; common sources oral hygiene products, foods and lip products; 82.6% also reacted to at least one other fragrance or plant allergen. 0.6% allergic Methods, limits and funding Outcomes: Allergic reaction rate Limitations: Patients were already being tested for suspected skin allergy, so 0.6% does not describe the general public. Funding and conflicts: Not stated in abstract Read: abstract
Weerts ZZRM 2018 A Novel Ileocolonic Release Peppermint Oil Capsule for Treatment of Irritable Bowel Syndrome: A Phase I Study in Healthy Volunteers. Adv Ther · PMID 30284674 · DOI	Randomised double blind crossover phase I	8 8 healthy volunteers (50% female, median age 22)	Small-intestine-release vs ileocolonic-release peppermint oil oil 182 mg single dose; washout over 14 days · vs small-intestine-release capsule	Time to peak 360 vs 180 min and lag time 225 vs 37 min (both longer for ileocolonic release); AUC 2331 vs 2623 micrograms h/L (smaller, significant); peak and half-life did not differ. Tmax median 360 vs 180 min Methods, limits and funding Outcomes: Menthol glucuronide in blood Limitations: Eight people; blood levels stand in for delivery to the colon. Registration: NCT02291445 Read: abstract
Weerts ZZRM 2020 Efficacy and Safety of Peppermint Oil in a Randomized, Double-Blind Trial of Patients With Irritable Bowel Syndrome. Gastroenterology · PMID 31470006 · DOI	Controlled trial	189 Adults with IBS (Rome IV), Netherlands, mean age 34, 77.8% women	Small-intestinal-release or ileocolonic-release peppermint oil capsules leaf (essential oil) 182 mg per capsule (small-intestinal or ileocolonic release) 8 weeks · vs Placebo	Pain response: 46.8% (small-intestinal release), 41.3% (ileocolonic release), 34.4% placebo; none statistically different from placebo. Small-intestinal release did lower secondary scores for abdominal pain (P=.016), discomfort (P=.020) and IBS severity (P=.020). Adverse events were mild but more common with peppermint oil. Primary endpoints not met (P=.170 and P=.385 for pain response). Methods, limits and funding Outcomes: FDA abdominal pain response and EMA overall relief (primary); pain, discomfort, severity (secondary) Limitations: Primary endpoints missed; secondary results are exploratory. Reported in the abstract only to this level of detail. Read: abstract
Yamamoto 2006 Efficacy of peppermint oil as an antispasmodic during endoscopic retrograde cholangiopancreatography. J Gastroenterol Hepatol · PMID 16911682 · DOI	Case series	40 Patients having ERCP (bile duct endoscopy)	Peppermint oil solution sprayed around the duodenal papilla leaf (essential oil) 20 mL of 1.6% or 3.2% solution Single procedure · vs Historical controls given glucagon (16 patients)	Duodenal movement none or mild in 69.2%. ERCP was completed with peppermint alone in 91.4% (37 of 39). No serious complications related to peppermint oil. 91.4% managed with peppermint alone. Methods, limits and funding Outcomes: Duodenal movement, need for extra antispasmodic Limitations: Not randomised; historical controls; small. Read: abstract
Zhao 2022 Peppermint essential oil: its phytochemistry, biological activity, pharmacological effect and application. Biomed Pharmacother · PMID 35994817 · DOI	Narrative review mixed	Literature on peppermint essential oil	Peppermint essential oil oil varied varied · vs varied	Oil is mainly menthol, menthone, neomenthol and isomenthone; reported effects include anti-inflammatory, antibacterial, antiviral and antioxidant activity, mostly lab and animal. Clinically used for gut and skin conditions per the authors. Methods, limits and funding Outcomes: Phytochemistry, activities, toxicity and uses Limitations: Narrative review with an emphasis on burn wounds and psoriasis; many claims rest on animal or lab work. Read: abstract
Zhao 2025 Characterization, differentiation, and adulteration detection of peppermint essential oil: An NMR approach. J Pharm Biomed Anal · PMID 40339205 · DOI	Other in-vitro	50 50 commercial peppermint essential oil samples	NMR analysis oil	High adulteration rate (42%) in the 50 commercial peppermint oils; adulterants included synthetic chemicals, de-mentholised cornmint oil and lower-cost oils. 42% adulterated Methods, limits and funding Outcomes: Adulteration Limitations: Mostly essential oils; supplement capsules not tested. Funding and conflicts: Funding from doTERRA International LLC and USDA ARS reported Read: abstract
de Groot 2016 Essential Oils, Part V: Peppermint Oil, Lavender Oil, and Lemongrass Oil. Dermatitis · PMID 27775966 · DOI	Review	Review of contact allergy to peppermint oil	Peppermint oil oil	Review of botanical origin, composition, contact allergy and allergic contact dermatitis from peppermint, lavender and lemongrass oils. Only the abstract was read; numbers are not in it. Methods, limits and funding Outcomes: Contact allergy and allergenic ingredients Limitations: Abstract only. Read: abstract
s-ema-ar-mentha-piperita-2020 EMA/HMPC assessment report on Mentha x piperita L., folium and aetheroleum (Revision 1, EMA/HMPC/522409/2013, final 15 January 2020) · Source	Authoritative guidance n/a			Methods, limits and funding Read: full-text
s-gbif-mentha-piperita GBIF Backbone: Mentha x piperita L. (usageKey 8707933) · Source	Reference database n/a			Methods, limits and funding Read: full-text
s-ncbi-taxonomy-34256 NCBI Taxonomy: Mentha x piperita (taxid 34256) · Source	Reference database n/a			Methods, limits and funding Read: full-text
s-pubchem-peppermint-compounds PubChem compound records for peppermint constituents · Source	Reference database n/a			Methods, limits and funding Read: full-text
Şancı 2023 Effect of peppermint-lemon aromatherapy on nausea-vomiting and quality of life in pediatric patients with leukemia: A randomized controlled trial. J Pediatr Nurs · PMID 37453895 · DOI	Controlled trial	90 Children aged 2-12 with leukaemia having chemotherapy	Diffused peppermint and lemon oils leaf (essential oil) plus lemon oil Diffuser Across chemotherapy cycles · vs Placebo (water diffuser) and no-intervention control	The peppermint-lemon group had lower nausea scores, better quality of life and lower pulse and respiratory rates than the other groups. Greater drop in nausea index across cycles than controls (numbers not in abstract). Methods, limits and funding Outcomes: Index of Nausea, Vomiting and Retching; quality of life; pulse Limitations: Mixed oils; allocation 'randomised groups' not detailed; one earlier review found diffused aromatherapy in children gave no benefit. Read: abstract

What we do not know yet

What the evidence supports: for indigestion, a peppermint and caraway oil mix (moderate certainty, 2023); for IBS, a possible small benefit from coated oil in older and pooled studies that the largest recent trials did not confirm. Everything else is weak.
IBS trials disagree: the biggest recent adult trials (2020, 2021) and a 2026 children's trial did not beat placebo. Pooled reviews rate their evidence very low quality. Long-term benefit and the best coating are unknown.
No placebo-controlled trial of peppermint tea was found for IBS or indigestion; tea doses are traditional only. The peppermint and caraway mix cannot show what peppermint alone does.
The headache evidence is one 1996 trial of 41 adults from one research group, with no recent independent repeat.
No trial of peppermint in people with reflux disease was found; the valve-relaxing effect comes from regulator statements and older studies, and a small test (8 people) did not show it.
No case of liver injury from peppermint was found, but our PubMed search was limited. We could not read the NIH LiverTox, German Commission E or WHO entries, so nothing is claimed about them.
The felodipine finding rests on one 12-person single-dose study with a very wide range, and the cyclosporine finding is from rats. Interactions with coated capsules and with diabetes or blood pressure medicines were not tested.
Infant harm from menthol is described in EU and NIH guidance; we did not read the original infant case reports. No data on peppermint oil capsules in pregnant women were found.
The EU peppermint oil dosing text was read as the final 2020 monograph in the safety review and as a 2007 draft elsewhere; where they agree it is quoted, and a 2026 EU call for new data was seen only in summary.
Many aroma, nausea, exercise and anxiety studies are small, hard to blind and mix oils, so peppermint's own effect is hard to judge. Product quality: two surveys found many peppermint oils adulterated, but no survey of capsules was verified.

How new research is added

New studies are found by a saved PubMed search and are placed in a review queue. A person reads each one before it changes any evidence rating, safety wording or dose information. New publications never change ratings automatically.

Lab markers

What changed in blood or saliva tests during trials. A changed number is not the same as feeling or being healthier, and we give no "normal ranges".

Other 16

▼

Headache pain intensity

Lowered in trials

How strong a headache feels, rated by the person on a diary scale or visual scale.

Low certainty

Results and what it means

Why it was measured

The main outcome of any headache treatment.

Statistical vs. clinical meaning

Self-rated pain is a clinical outcome; the benefit for tension headache is statistically significant in one trial and the amount of relief was not given in the abstract.

Safety implication

Skin or nasal irritation is the main concern.

Study	Result	People	Product
⁴³	10% oil lowered intensity versus placebo from 15 minutes (p<0.01) for 1 hour; similar to acetaminophen 1,000 mg	41 adults with tension-type headache	Peppermint oil 10% in ethanol on forehead and temples
¹¹⁴	Intensity differed between groups after treatment (P<0.001); about 42% of peppermint and 41.5% of lidocaine groups responded considerably	120 adults with migraine	Peppermint oil 1.5% nose drops
¹³⁰	28% pain-free, 28% mild at 2 hours; majority similar or improved; 12 of 25 used rescue medicine	25 adults with migraine	Menthol 6% gel at skull base
⁶⁹	No added improvement in pain over a foot bath alone	46 teens with chronic headache	Foot bath plus peppermint oil

^{43 114 130 69}

↕

Cognitive task performance

Mixed results in trials

Scores on computer tests of attention, memory and speed.

Very low certainty

Results and what it means

Why it was measured

Used in lab studies to see if a substance sharpens thinking.

Statistical vs. clinical meaning

Lab-test gains do not necessarily translate to better real-life memory or work.

Safety implication

None directly.

Study	Result	People	Product
⁶⁵	Higher dose improved Rapid Visual Information Processing at 1 and 3 hours; both doses improved Serial 3s subtraction at 3 hours (values not in the abstract)	24 healthy adults	50 or 100 microlitres of oil in a capsule
¹⁰⁰	Peppermint enhanced memory factors versus no aroma	144 healthy volunteers	Peppermint aroma
⁵¹	No improvement in a vigilance task with peppermint	Healthy volunteers	Peppermint aroma
¹³²	False alarms in brain-injured observers resembled controls with peppermint scent	People with brain injury and controls	Peppermint scent whiffs

^{65 100 51 132}

▼

Rated fatigue and sleepiness

Lowered in trials

Self-rated tiredness on scales such as the Fatigue Severity Scale or Karolinska Sleepiness Scale.

Low certainty

Results and what it means

Why it was measured

Shows whether people feel less tired.

Statistical vs. clinical meaning

Subjective scales; participants cannot be blinded to a strong smell; clinical size of the change was not stated.

Safety implication

None directly.

Study	Result	People	Product
⁸³	Fatigue fell more than with placebo (P<0.001); no difference from lavender	105 cardiac patients	3 drops peppermint oil inhaled for 7 nights
¹⁴⁰	Aroma group had much greater fall in burnout rating than rose-water group	14 people with mental exhaustion	Peppermint, basil, helichrysum inhaler
⁶⁰	Lower rated driving fatigue than control; not shown to beat grapefruit or lavender	Drivers in a driving task	Peppermint scent

^{83 140 60}

▼

Pupil fatigue oscillation (sleepiness index)

Lowered in trials

Small rhythmic changes in pupil size that grow larger as a person becomes sleepier; used as an objective sleepiness measure.

Very low certainty

Results and what it means

Why it was measured

Gives a measurable sleepiness number that does not depend on the person's opinion.

Statistical vs. clinical meaning

One preliminary lab study; whether this changes everyday alertness is not shown.

Safety implication

None.

Study	Result	People	Product
¹⁰⁶	Peppermint limited the rise in sleepiness over 11 minutes in a dark room versus no odour; unrelated to starting self-rated sleepiness	Adult volunteers (number not in abstract)	Peppermint oil aroma

¹⁰⁶

▼

EEG alpha/beta ratio (driving fatigue)

Lowered in trials

A brain-wave ratio that rises when a person becomes drowsy.

Very low certainty

Results and what it means

Why it was measured

Used in the driving study as an objective fatigue marker.

Statistical vs. clinical meaning

A research marker; the abstract does not give sample size or values.

Safety implication

None.

Study	Result	People	Product
⁶⁰	R(alpha/beta) fell significantly after scent use; lower in all three scent groups than control	Drivers	Peppermint, grapefruit or lavender scent

⁶⁰

▼

Rated anxiety and stress

Lowered in trials

Anxiety and stress scores from questionnaires or simple faces scales.

Very low certainty

Results and what it means

Why it was measured

Shows how worried or tense people feel.

Statistical vs. clinical meaning

Statistically significant but short-lived and self-rated; the clinical size is not clear.

Safety implication

None directly.

Study	Result	People	Product
¹²³	Anxiety 24.64 to 19.55 and stress 25.00 to 17.18 (P<0.001) versus saline	Patients with acute coronary syndrome	0.2 mL peppermint oil on an eye pad, 20 minutes
²	Score change: peppermint -0.68, lavender -1.80, chamomile -2.04, control +0.04	100 children, dental treatment	Nebulised peppermint
⁴⁶	Both aroma groups reduced more than control (p<0.05); lavender vs lavender-peppermint no difference	135 women before breast biopsy	Lavender or lavender-peppermint pad
⁷⁹	Lower anxiety scores in the first 2 postoperative days (P<0.05)	178 older surgical patients	Inhaled peppermint oil

^{123 2 46 79}

↕

Heart rate and blood pressure (during anxiety trials)

Mixed results in trials

How fast the heart beats and the pressure in the arteries; both rise with stress.

Very low certainty

Results and what it means

Why it was measured

Used as a physical sign of stress in the aromatherapy trials.

Statistical vs. clinical meaning

Short-term and from a single heart-emergency trial; the drop in blood pressure is unusually large and needs repeating.

Safety implication

Not for treating blood pressure; talk to the care team.

Study	Result	People	Product
¹²³	Systolic pressure fell from 139.77 to 126.36 mmHg (P<0.001); diastolic pressure, heart rate and pain also lower vs placebo	Patients with acute coronary syndrome	0.2 mL peppermint oil on an eye pad
²	Oxygen saturation did not differ between groups; pulse fell most with chamomile	100 children	Nebulised oils

^{123 2}

▼

Postoperative delirium (3 days)

Lowered in trials

The share of patients who develop sudden confusion after surgery.

Very low certainty

Results and what it means

Why it was measured

A key complication in older surgical patients.

Statistical vs. clinical meaning

Borderline and unreplicated.

Safety implication

Not a replacement for hospital delirium prevention.

Study	Result	People	Product
⁷⁹	7.9% vs 19.1% (RR 0.412; 95% CI 0.179 to 0.944; P=0.048)	178 older patients, joint replacement	Inhaled peppermint oil vs saline

⁷⁹

↕

Time to exhaustion

Mixed results in trials

How long someone can keep exercising at a set effort before stopping.

Very low certainty

Results and what it means

Why it was measured

Common endurance test.

Statistical vs. clinical meaning

Positive and null results; tiny studies; not a health outcome by itself.

Safety implication

None directly.

Study	Result	People	Product
⁹⁷	109.9 vs 98.5 min (p=0.009; effect size 0.826)	14 recreational runners	Oil in water before and during run
⁹¹	664.5 to 830.2 s after 10 days (p<0.001), no clear control group	12 healthy men	0.05 mL oil in 500 mL water daily
¹²⁵	583.33 vs 587.04 s: no difference	7 healthy adults	Oil, 10 days
¹¹³	No effect of inhaled peppermint on running time	36 women soccer players	Inhaled odour

^{97 91 125 113}

●

Perceived effort (RPE) and thermal sensation

No clear change in trials

How hard or how hot exercise feels to the person.

Low certainty

Results and what it means

Why it was measured

If peppermint or menthol made exercise feel easier or cooler it could explain performance gains.

Statistical vs. clinical meaning

Consistent lack of effect across three sources, but all are small.

Safety implication

None.

Study	Result	People	Product
⁹⁷	No change in perceived effort, thermal sensation or comfort even though time to exhaustion rose	14 runners	Peppermint oil drink
¹⁴²	No change in perceived exertion or thermal comfort with menthol gel in heat	14 trained runners	Menthol 0.5% gel
¹³¹	Menthol rinse improved cooling sensation but not performance in hot conditions	20 studies pooled	Menthol mouth rinse

^{97 142 131}

↕

Colonic spasm score during colonoscopy

Mixed results in trials

How much the bowel wall squeezes and tightens as the doctor sees it through the scope, graded by the endoscopist.

Low certainty

Results and what it means

Why it was measured

Spasm makes the scope harder to move and the bowel wall harder to see.

Statistical vs. clinical meaning

Scored by the endoscopist rather than measured by an instrument. Results are positive for oil put straight into the colon and null for the largest oral-capsule trial.

Safety implication

No safety concern reported in the abstracts.

Study	Result	People	Product
¹³	Any spasm: risk difference -0.39 (P=0.02); severe spasm -0.15 (P=0.04); peristalsis -0.27 (P<=0.001)	Adults having colonoscopy, 6 studies pooled	Peppermint oil, routes varied
¹²¹	Complete absence of spasm 58.3% vs 45.8% (P=0.05)	48 adults having screening colonoscopy	50 mL peppermint oil through the scope vs placebo
¹²⁴	Lower spasm score with peppermint capsules; values not in the abstract	65 adults	Colpermin capsules 4 h before vs placebo
⁴⁵	Insertion 1.23 vs 1.2 (p=0.9); withdrawal 1.3 vs 1.23 (p=0.72); polypectomy 0.52 vs 0.46 (p=0.69)	Adults having colonoscopy	Oral IBgard vs placebo

^{13 121 124 45}

↕

Time to reach the caecum during colonoscopy

Mixed results in trials

Minutes from inserting the scope until it reaches the start of the large bowel.

Low certainty

Results and what it means

Why it was measured

A shorter time suggests an easier procedure.

Statistical vs. clinical meaning

A few minutes' difference may be of limited importance to patients; one of three trials found none.

Safety implication

No safety concern reported in the abstracts.

Study	Result	People	Product
¹²¹	7.2 vs 10.3 min (P=0.04)	48 adults	Peppermint oil through the scope vs placebo
¹²⁴	Shorter in the peppermint group; values not in the abstract	65 adults	Colpermin capsules vs placebo
⁶	No difference	80 adults	Colpermin capsules vs placebo

^{121 124 6}

↕

Adenoma detection rate at colonoscopy

Mixed results in trials

The share of procedures in which the doctor finds at least one adenoma (a growth that can become cancer).

Very low certainty

Results and what it means

Why it was measured

A quality measure for colonoscopy; better visualisation might raise it.

Statistical vs. clinical meaning

The pooled gain rests on two studies and the individual trials were not significant, so this is not a reliable benefit.

Safety implication

No safety concern reported in the abstracts.

Study	Result	People	Product
¹³	RR 1.31 (P=0.01), only two studies measured it	Adults having colonoscopy	Peppermint oil
¹²¹	45.8% vs 37.5% (P=0.56)	48 adults	Peppermint oil through the scope vs placebo
⁴⁵	47.8% vs 43.1% (p=0.51)	Adults having colonoscopy	Oral IBgard vs placebo

^{13 121 45}

▼

Time for gastric contraction rings to disappear at endoscopy

Lowered in trials

Seconds until the squeezing rings in the stomach outlet area relax after the drug is given.

Low certainty

Results and what it means

Why it was measured

Shows how fast a drug calms stomach muscle during an endoscopy.

Statistical vs. clinical meaning

Measured on camera by the study team; one trial.

Safety implication

Hyoscine caused dry mouth, blurred vision and urinary retention in the trial; no significant side effects with peppermint oil.

Study	Result	People	Product
⁵²	97.1 seconds with peppermint oil vs 185.9 seconds with hyoscine injection (p<0.0001)	100 patients having upper endoscopy	Peppermint oil solution into the stomach vs injected hyoscine

⁵²

▼

Simultaneous contractions of the food pipe

Lowered in trials

Squeezes in several parts of the food pipe at once instead of in sequence; seen on a pressure test.

Very low certainty

Results and what it means

Why it was measured

This pattern is a sign of oesophageal spasm and can cause chest pain and trouble swallowing.

Statistical vs. clinical meaning

A pressure change in 8 people minutes after one dose does not show lasting symptom relief.

Safety implication

Not reported in the abstract.

Study	Result	People	Product
¹¹¹	Simultaneous contractions eliminated in all 8 patients (p<0.01); variability of amplitude 33.4 to 24.9 mm Hg (p<0.05)	8 patients with diffuse oesophageal spasm	5 drops peppermint oil in 10 mL water, measured 10 minutes later

¹¹¹

▼

Time to first bowel sound and first gas after surgery

Lowered in trials

Hours from the end of surgery until a bowel sound is heard and the person passes gas, signs the bowel is waking up.

Not enough evidence

Results and what it means

Why it was measured

Earlier return means less ileus and an easier recovery.

Statistical vs. clinical meaning

One trial; the abstract says mint, not peppermint.

Safety implication

No harms reported in the abstract.

Study	Result	People	Product
¹⁰¹	First bowel sound 5.78 vs 9.05 hours; first gas 7.87 vs 12.24 hours	102 women after Caesarean section	Mint drops vs placebo drops

¹⁰¹

Dosage and forms

What researchers actually gave people in trials. These are study numbers, not advice for you.

180–360mg of extract a day in most trials

4–5weeks is how long most trials lasted

180–540mg a day: the full range tested

3studies with a stated dose

Study doses are not advice and may not suit you. Ask a clinician or pharmacist.

How to read these numbers: four different kinds of dose

Four kinds of number must not be mixed. (1) Studied doses. In IBS trials the oil was usually taken as an enteric-coated capsule about three times a day for 4 to 8 weeks. Where the dose is stated: 180 mg three times a day for 6 weeks (Nee 2021, no benefit over placebo), 182 mg per dose for 8 weeks (Weerts 2020, main goals missed), and in children 182 mg twice or three times a day for 8 weeks (Vermeijden 2026, no benefit). Many older abstracts give no milligrams. In functional dyspepsia the studied product was a capsule of 90 mg peppermint oil with 50 mg caraway oil, one or two a day, for 4 weeks. For headache the studied product was a 10% oil in ethanol solution rubbed on forehead and temples. For nausea, inhaled 2% oil around surgery. (2) Label serving sizes are chosen by the maker and may not match any trial. A capsule may hold different oil strengths, coatings or blends. (3) Official guidance. The EU peppermint LEAF monograph (final, 2020, traditional use only) lists a tea of 1.5 to 3.0 g of leaf in 100 to 150 ml of boiling water three times a day for adults, and says to see a doctor if symptoms last more than 2 weeks. The 2007 DRAFT EU peppermint OIL monograph lists 0.2 to 0.4 ml in gastro-resistant capsules up to three times a day, before meals, taken until symptoms settle (usually 1 to 2 weeks), and up to 3 months per course if symptoms persist. We did not read a later final oil text. The EMA limit for pulegone plus menthofuran is 0.75 mg per kg of body weight a day for lifelong use, or 75 mg a day for under a year. (4) Enteric coating matters. The draft EU monograph says capsules must be swallowed whole, because chewing or breaking them releases the oil early and may irritate the mouth and food pipe. It also says food or antacids taken at the same time may release the contents early, and acid-lowering medicines (histamine-2 blockers, proton pump inhibitors) can dissolve the coating early and should be avoided. People who already have heartburn may find it worse. Tea versus oil: peppermint tea is a leaf infusion with a small amount of oil in it; the capsules deliver a concentrated oil to the gut. We found no IBS or dyspepsia trial of plain peppermint tea, so tea doses come from traditional use only, not from trials. None of these numbers is a prescription. People who are pregnant or breastfeeding, have gallstones or liver disease, or take acid-lowering medicines should ask a clinician first.

Doses used in studies 3

IBS severity (IBS-SSS)

Adults with IBS (Rome IV), moderate to severe, one US centre · compared with placebo (randomised 1 to 2)

540 mg a day

180 mg three times a day · 6 weeks

Enteric-coated peppermint oil capsule · aerial parts (oil)

What the trial found

Both groups improved a lot (oil 90.8 points, placebo 100.3 points). The oil was not better than placebo (P=0.97, effect size d=-0.11), nor on any secondary measure.

¹⁰³

Pain; pressure, heaviness, fullness; doctor-rated global improvement

Outpatients with functional dyspepsia · 96 people · compared with placebo

180 mg a day

One capsule (90 mg peppermint oil + 50 mg caraway oil) twice a day · 28 days

Fixed combination of peppermint oil and caraway oil, enteric-coated capsule (Enteroplant) · aerial parts (oil) + caraway fruit oil

What the trial found

Average pain fell 40% vs 22% with placebo; pressure/fullness fell 43% vs 22%; 67% vs 21% were much or very much improved. All three were statistically significant.

⁸⁷

Pain on a 10-point scale

Outpatients with functional dyspepsia · 118 people · compared with cisapride 10 mg three times a day (no placebo)

180 mg a day

2 capsules a day, each 90 mg peppermint oil + 50 mg caraway oil · 4 weeks

Peppermint oil plus caraway oil, enteric-coated capsule (Enteroplant) · aerial parts (oil) + caraway fruit oil

What the trial found

Pain fell 4.62 points with the oil mix and 4.60 with cisapride, judged equivalent (P=0.021). Adverse events: 12 patients (oil mix) vs 14 (cisapride).

⁸¹

Traditional preparations Ayurveda, not clinical dosing

Herbal tea (infusion) of dried peppermint leaf

European (EU traditional herbal medicine monograph)

Adults and elderly: 1.5 to 3.0 g of leaf in 100 to 150 ml of boiling water, 3 times a day. Children 4 to 11 and adolescents: 1.0 to 2.0 g in 100 to 150 ml, 3 times a day. Not recommended under 4 years.

Final EU monograph, revision 1, 15 January 2020. For the symptomatic relief of digestive problems such as dyspepsia and flatulence, based on long-standing use only; the EMA does not claim trial-proven efficacy. See a doctor if symptoms last more than 2 weeks.

Tincture of peppermint leaf (1:5; ethanol 45% or 70%)

European (EU traditional herbal medicine monograph)

Adults and elderly: 2.0 to 3.0 ml, 3 times a day

Same monograph; alcohol labelling is required. Pregnancy and breastfeeding: use not recommended (no safety data).

Peppermint oil rubbed on forehead and temples (10% in ethanol)

European (EU draft monograph, listed as well-established use for mild tension-type headache)

10% oil in ethanol, up to three times a day, rubbed on forehead and temples, repeated every 15 minutes in the draft text

2007 consultation draft; the final text was not read. Not for children and adolescents under 18. Avoid eye contact; do not apply to broken skin.

Steam inhalation of peppermint oil

European (EU draft monograph, traditional use for coughs and colds)

Adolescents over 12 and adults: 2 to 4 drops added to hot water, inhaled up to three times a day, not for more than 2 weeks

2007 draft; not for children under 2 (menthol can trigger reflex apnoea and laryngospasm in babies) or children with seizure history, per the draft contraindications.

Peppermint oil on the skin for muscle aches or itch; in lozenges or oral spray

European (EU draft monograph, traditional use)

Skin: for adults, oily or semi-solid products 5 to 20%, aqueous-ethanol 5 to 10%; nasal ointments 1 to 5%. Mouth: 2 to 3 drops (0.08 to 0.12 ml), 3 to 4 times a day, in lozenges or spray.

One trial, open-label arm.

¹⁴¹

Safety

What studies and official sources say about side effects, medicines and who should check first. Each point shows what kind of evidence it comes from.

Main points to know 10

Heartburn and reflux: peppermint can make it worse, which is why oil capsules are coated. The EU assessment report says both peppermint leaf and peppermint oil relax the lower oesophageal sphincter, the muscle valve between the food pipe and the stomach, so acid can rise more easily. The EU leaf monograph tells people with reflux to avoid peppermint leaf preparations. The EU oil monograph says people who already have heartburn or a hiatal hernia sometimes get worse and should stop. NCCIH lists heartburn as a possible oral side effect and says capsules are often enteric-coated to reduce it. One small human study measured sphincter pressure in 8 people with oesophageal spasm and found it did not change 10 minutes after 5 drops of oil, so the sphincter effect is stated by regulators but was not seen in that test. We found no trial of peppermint in people with reflux disease. Authoritative guidance ^{31 30 29 102 111}
Enteric-coated capsules are meant to open lower down; chewing them or taking them with acid-lowering medicine can undo that. Gastro-resistant (enteric-coated) capsules are designed to release the oil in the intestine instead of the stomach. In a 16-man crossover study, total menthol absorbed was equivalent between coated and uncoated capsules (90% CI 97 to 105%), but the coated capsules peaked later (3.0 h versus 1.7 h) and lower (1196 versus 1492 ng/ml). The EU oil monograph says capsules must be swallowed whole, because chewing or breaking them can release the oil early and irritate the mouth and food pipe, and says food or antacids taken at the same time could release the contents early, while acid-lowering medicines such as H2 blockers and proton pump inhibitors may dissolve the coating too soon and should be avoided. The assessment report describes one person with no stomach acid (achlorhydria) whose coated capsule opened in the stomach with heartburn and belching. The EU monograph says to take capsules 30 minutes before meals. Authoritative guidance ^{84 29 31}
Allergy and skin reactions are real but not common in the studies we found. In North American patch-test data, 161 of 28,128 people tested (0.6%) were allergic to 2% peppermint oil; most were women over 40, the face and lips were the most common sites, and common sources were toothpaste and mouthwash, foods and lip products. These were people already being tested for skin allergy, so the figure does not describe the general public. A Glasgow case series found 12 patients with menthol or peppermint sensitivity causing mouth burning, ulcers or lichenoid reactions, and 6 of the 9 followed up improved when they avoided both. The EU monograph lists skin rash, contact dermatitis and eye irritation for skin use, and allergic reactions to menthol with headache, slow heart rate, tremor, unsteadiness, rash and anaphylactic shock after oral use, all with unknown frequency. Allergy to peppermint or menthol is a listed contraindication. Retrospective cohort ^{146 99 29 50 152}
Infants and young children: do not put peppermint oil or menthol near the face. NCCIH says peppermint oil should not be applied to the face of infants or young children because menthol can cause serious harm if they inhale it. The EU oil monograph contraindicates the inhaled, mouth and skin uses under 2 years of age because menthol can cause reflex apnoea (breathing stops) and laryngospasm (the voice box clamps shut), and also contraindicates them in children with a history of seizures. The assessment report adds that the nose is a reflex organ in small children and that applying peppermint preparations to open skin, nose, face and chest of small children is not recommended. In newborn dogs, menthol in the upper airway cut breathing to about 53% of control. Human infant cases are described in the regulatory documents but we did not read the original reports. Authoritative guidance ^{102 29 31 119}
Pulegone: a liver-toxic compound in peppermint oil, much more in pennyroyal. Pulegone and menthofuran make up 1 to 11% of peppermint oil by the EU oil monograph; the assessment report gives a maximum pulegone of 3% for the oil. In rats, pulegone and its breakdown products damaged the liver and kidney and caused liver and urinary tract tumours at high doses; the EU calls them non-genotoxic carcinogens whose effect depends on sustained cell damage at high doses. The EU therefore requires the combined daily pulegone and menthofuran intake from a medicine to stay below 37.5 mg for an adult (0.75 mg/kg for a child). For the highest labelled oral dose (1.2 ml a day) the assessment report calculated that oil at the maximum Ph. Eur. limits would give about 99 to 100 mg a day of the two together, which is above that limit, so products must specify and control pulegone and menthofuran content. Pennyroyal (Mentha pulegium) is a different mint rich in pulegone: a case series reported one death among four ingestions and moderate to severe toxicity from at least 10 ml of its oil. This is why Mentha piperita and Mentha pulegium must not be confused. Authoritative guidance ^{29 31 138 9 133}
Liver: no peppermint-oil liver injury found, but the EU lists liver disease as a reason not to take the oral oil. Our PubMed searches did not find a case report of liver injury attributed to peppermint oil or peppermint tea, and the EU assessment report describes no such case. The animal evidence is mixed: a 28-day rat study found pulegone damaged the liver at 80 mg/kg a day and above and menthol enlarged the liver and vacuolated liver cells at 200 mg/kg a day and above. The EU oil monograph contraindicates the oral gut-spasm use in people with liver disease, cholangitis and bile-duct disorders. We could not read the NIH LiverTox database for peppermint, so we cannot report whether it holds an entry or score; the pennyroyal poisoning cases are a separate plant and do not transfer. Authoritative guidance ^{29 138 9}
Drug interactions: a possible rise in felodipine and cyclosporine levels; acid-lowering drugs can break the capsule coating. In 12 healthy volunteers, 600 mg of peppermint oil raised felodipine exposure (AUC) to 140% of the water value, with a wide individual range of 77 to 262%; grapefruit juice raised it to 173%. In the lab, peppermint oil and menthol inhibited the liver enzyme CYP3A4 that breaks down many medicines. In rats, peppermint oil roughly tripled cyclosporine peak levels. Menthol alone, in 10 volunteers, did not change felodipine levels or blood pressure. The EU oil monograph says acid-lowering medicines (H2 blockers, proton pump inhibitors) and antacids can dissolve the coating early. Two case reports link menthol cough drops with a drop in warfarin INR. We found no human interaction studies with diabetes or blood pressure medicines. Controlled trial ^{24 143 37 29 64 21}
Large doses of oil are dangerous; the safe-use window is the labelled dose. The EU monograph says oral overdose may cause severe stomach and bowel symptoms, diarrhoea, rectal ulceration, seizures, loss of consciousness, apnoea and heart rhythm disturbances, probably from menthol, and inhaled large doses may cause dizziness, confusion, muscle weakness, nausea and double vision. The assessment report cites a near-fatal suicidal ingestion of peppermint oil (coma and shock, recovered in 24 hours; amount not stated) that we did not read directly. A case report describes an 18-year-old who injected peppermint oil into a vein and developed life-threatening lung injury. Keep oil out of reach of children and never swallow undiluted essential oil. Authoritative guidance ^{29 31 15}
Pregnancy, breastfeeding and children: not enough safety data for medicinal use. Both EU monographs say safety in pregnancy and breastfeeding has not been established and advise against medicinal use; the oil monograph says it is unknown whether peppermint oil constituents pass into breast milk, while LactMed says menthol and 1,8-cineole pass into milk in small amounts. NCCIH says amounts found in food are likely safe in pregnancy and breastfeeding but little is known about medicinal amounts. LactMed notes peppermint is used to reduce milk supply based on laboratory and high-dose animal findings, and advises applying peppermint to the nipples only after nursing and wiping it off before the next feed. For children, the oral gut-spasm capsules are not recommended under 8 and the headache rub not under 18; peppermint leaf tea is not recommended under 4. Authoritative guidance ^{29 30 102 1}
Most people in IBS trials tolerated peppermint oil, but side effects were more frequent than with placebo in the newest review. Across 12 trials (835 people), adverse effects occurred in 9.3% on peppermint oil and 6.1% on placebo (RR 1.40, 95% CI 0.87 to 2.26). A 2022 update of 10 trials (1030 people) found adverse events significantly more frequent with peppermint oil (RR 1.57, 95% CI 1.04 to 2.37) and rated the evidence quality very low. A review of 16 trials describes the typical effects as mild, temporary heartburn and anal or perianal burning. Meta-analysis ^{8 58 39}

Side effects 10

Effect	How often	Severity and recovery	Evidence
Heartburn Reduced but not removed by enteric coating. More likely if capsules are chewed, taken with antacids or acid-lowering medicine, or by people with reflux or hiatal hernia.	Described as frequent in clinical trials by the EU oil monograph; no percentage given in the sources we read.	mild Usually reversible on stopping	Authoritative guidance ^{29 31 39 102}
Perianal (anal) burning Described by the review as typical for peppermint oil taken in capsules, along with heartburn.	Described as frequent in clinical trials (EU oil monograph); no percentage in the abstracts read.	mild Reversible	Authoritative guidance ^{29 39}
Nausea, vomiting, dry mouth, blurred vision NCCIH lists nausea, abdominal pain and dry mouth.	Listed as frequent in clinical trials by the EU oil monograph; no percentages given.	mild Reversible	Authoritative guidance ^{29 31 102}
Menthol-smelling urine and stools; painful urination; inflammation of the glans of the penis Reported in the monograph with no figures or case details in the sources we read.	Frequency not known (EU oil monograph)	mild to moderate Reversible	Authoritative guidance ²⁹
Allergic contact dermatitis (skin, lips, mouth) Not the rate in the general public. 82.6% of allergic patients also reacted to another fragrance or plant allergen.	0.6% of 28,128 people patch tested (a group already suspected of skin allergy)	mild to moderate Usually clears with avoidance	Retrospective cohort ^{146 99 29}
Allergic reaction to menthol with headache, slow heart rate, tremor, unsteadiness, rash, or anaphylactic shock The assessment report mentions anaphylactic shock reported in Germany (BfArM); NCCIH calls allergic reactions rare.	Frequency not known	potentially serious Variable	Authoritative guidance ^{29 31 102}
Apnoea (breathing stops), bronchospasm and laryngospasm in hypersensitive people, especially infants This is why the inhaled, mouth and skin uses are contraindicated under 2 years.	Frequency not known	potentially serious Not stated	Authoritative guidance ^{29 31 102}
Skin and mucosal irritation, eye irritation Eye contact with unwashed hands after applying oil can irritate; do not apply to broken or irritated skin.	Frequency not known (EU oil monograph)	mild Reversible	Authoritative guidance ^{29 102}
Mouth and food pipe irritation from broken or chewed capsules Stated as a possibility by the EU oil monograph; no figures.	Not established	mild Reversible	Authoritative guidance ²⁹
Worsening of reflux and heartburn from peppermint leaf or tea The report says no serious adverse effects have been reported with normal, prolonged use of peppermint tea.	Frequency not known (EU leaf monograph)	mild Reversible	Authoritative guidance ^{30 31}

Liver

We found no case report of liver injury linked to peppermint oil, leaf or tea in our PubMed searches, and the EU assessment report describes none. We could not open the NIH LiverTox database, so we cannot say whether it has a peppermint entry or what score it gives; this is not verified. The liver concern comes from a component, pulegone (and its product menthofuran), which in rats caused liver and kidney damage and, over two years at high doses, liver tumours; the EU sets a daily limit for the pair in medicines. Pennyroyal (Mentha pulegium), a different mint rich in pulegone, has caused fatal liver poisoning, but peppermint oil contains far less. The EU oil monograph contraindicates the oral gut-spasm capsules in people with liver disease or bile-duct disorders as a precaution. ^{29 31 138 9 133}

How often. No peppermint cases found, so no rate can be given. The pennyroyal figures (one death in four ingestions; toxicity from at least 10 ml of oil in earlier cases) describe a different plant.

Monitoring. No guideline we read recommends routine liver tests for people using peppermint products; none found. People with known liver disease should ask their doctor before using oral peppermint oil.

This is a safety connection. It is not evidence that Peppermint supports liver health.

Medicines and supplements 5

With	Why it matters	Importance	Evidence	What to do
Felodipine (and possibly other medicines broken down by CYP3A4, such as some calcium channel blockers) prescription	Peppermint oil, menthol and menthyl acetate reversibly inhibited CYP3A4 in human liver microsomes. In 12 healthy volunteers, 600 mg peppermint oil with a 10 mg felodipine extended-release tablet raised felodipine AUC to 140% of the water value (range 77 to 262%, P under .05) and raised peak concentration. Grapefruit juice raised AUC to 173%. In a separate crossover of 10 volunteers, menthol capsules (200 mg over the day) did not markedly change felodipine levels or blood pressure.	Plausible rise in felodipine exposure shown in one small single-dose study with a very wide range. No effect on blood pressure was measured in that study. The EU assessment report notes calcium-channel antagonism of peppermint in animals and in vitro raises a possibility of interaction with other calcium blockers; this is theory.	Controlled trial Low certainty ^{24 37 31}	If you take felodipine or another medicine that carries a grapefruit warning, ask your pharmacist before using peppermint oil capsules regularly.
Cyclosporine prescription	In rats, peppermint oil 100 mg/kg tripled cyclosporine peak concentration (0.60 to 1.6 ug/ml) and raised AUC from 8.3 to 24.3 ug h/ml. The authors suggest CYP3A inhibition is not the only reason.	Animal data only; if the same happened in people, cyclosporine levels could rise. No human data found.	Animal research Very low certainty ¹⁴³	Transplant patients on cyclosporine should ask their transplant team before using peppermint oil.
Antacids, H2 blockers (such as famotidine) and proton pump inhibitors (such as omeprazole) prescription	Enteric coating is made to dissolve at the higher acidity change of the intestine; food or antacids at the same time could release the content early, and acid-lowering medicines may dissolve the coating too soon (EU oil monograph and assessment report). The report describes a patient with no stomach acid whose capsule opened in the stomach.	Premature release could mean heartburn, mouth or food-pipe irritation and less effect lower down. No trial quantifies it.	Authoritative guidance Low certainty ^{29 31}	Take capsules 30 minutes before meals and swallow whole; EU guidance says acid-lowering medicines should be avoided with the oral oil, so ask your doctor if you take a PPI or H2 blocker.
Warfarin (menthol cough drops) prescription	Two case reports: a 57-year-old man's INR fell from 2.28 to 2.68 down to 1.45 about a week after starting menthol cough drops; a 46-year-old man's INR fell from 2.6 to 1.6, stayed low despite dose rises and recovered to 2.9 five days after stopping 8 to 10 drops a day. Authors suggest menthol may act on liver enzymes.	Two case reports of menthol lozenges, not peppermint oil or tea. The EU report says the menthol dose is unknown so relevance to peppermint oil cannot be judged.	Case report Very low certainty ^{64 21 31}	If you take warfarin and use many menthol lozenges or peppermint oil products, mention it to your clinic and have the INR checked after a change.
Other products containing peppermint oil supplement	The EU oil monograph says other medicinal products containing peppermint oil should be avoided during treatment with it.	A label advice to avoid adding up the dose (including its pulegone and menthofuran); no study.	Authoritative guidance Not enough evidence ^{29 31}	Check labels for peppermint oil in chewing gum, sweets and balms if you also take oil capsules.

Who should check first 13

Situation	Advice	Evidence
Allergy to peppermint oil, peppermint leaf or menthol	Do not use. Listed as a contraindication in both EU monographs.	Authoritative guidance ^{29 30}
Children under 2 years: inhaled, mouth or skin peppermint oil or menthol	Do not use. EU contraindication because menthol can induce reflex apnoea and laryngospasm. NCCIH says never apply to the face of infants or young children.	Authoritative guidance ^{29 102 31}
Children with a history of seizures (febrile or not)	EU contraindication for the traditional inhaled, mouth and skin uses.	Authoritative guidance ²⁹
Liver disease, inflamed bile ducts (cholangitis) or other bile-duct disorders	EU contraindication for the oral gut-spasm capsules.	Authoritative guidance ²⁹
Gallstones	EU contraindication for the oral gut capsules; leaf tea and the other oil uses call for caution because peppermint may stimulate bile flow. Ask your doctor.	Authoritative guidance ^{29 30 31}
Achlorhydria (little or no stomach acid)	EU contraindication for oral gut capsules because a coated capsule can open in the stomach.	Authoritative guidance ^{29 31}
Heartburn, reflux disease or hiatal hernia	EU leaf monograph: avoid peppermint leaf preparations. EU oil monograph: these patients sometimes get worse; stop treatment if so.	Authoritative guidance ^{30 29 31}
Inflamed or ulcerated gut	EU oil monograph says use with caution.	Authoritative guidance ²⁹
G6PD deficiency	Precaution only. A study of 60 G6PD-deficient newborns found more jaundice when a mentholated powder was put on the cord, and the EU report advises caution for people with G6PD deficiency. No study of adults with G6PD deficiency using peppermint was found. Newborns should not be exposed to menthol products.	Non randomised trial ^{107 31}
Pregnancy	EU monographs do not recommend medicinal use because safety has not been established (oil headache rub: only if a doctor judges the benefit higher). NCCIH: food amounts are likely safe, medicinal amounts unknown. Ask your midwife or doctor.	Authoritative guidance ^{29 30 102}
Breastfeeding	Medicinal use is not recommended in the EU monographs. LactMed: peppermint is GRAS as a food; it has been used to reduce milk supply in some places; on the nipples, apply only after nursing and wipe off before the next feed.	Authoritative guidance ^{29 30 1 102}
Children and teenagers	EU: oral gut capsules not recommended under 8, the forehead headache rub not under 18, leaf tea not under 4, traditional uses not recommended at 2 to 11. One trial gave enteric-coated capsules to 42 children with IBS but its abstract has no safety data.	Authoritative guidance ^{29 30 71}
Organ transplant on cyclosporine, or taking felodipine	Ask your transplant team or pharmacist; levels may rise (small study in people, rat study).	Controlled trial ^{24 143}

Overdose, product quality and regulators

Summary. Peppermint oil is mainly toxic through menthol when swallowed in large amounts or inhaled by infants, and through pulegone and menthofuran with long-term high-dose exposure in animals. In tests peppermint oil itself was negative in two lab genotoxicity tests and an animal test; reproductive toxicity and carcinogenicity tests of the oil itself have not been done, according to the EU monograph.

Animal. EU: a 3-month rat study of pulegone found liver and kidney toxicity with a no-effect dose of 37.5 mg/kg; in 2-year studies pulegone caused liver and urinary tract tumours in rats and mice (clear evidence in female rats at 37.5 mg/kg and in mice at 37.5 mg/kg, none in male rats up to 75 mg/kg). The EU calls pulegone and menthofuran non-genotoxic carcinogens acting through sustained cell damage at high doses. In a 28-day rat study, pulegone at 80 and 160 mg/kg a day caused atonia, liver changes and cerebellar white-matter changes with a no-effect level of 20 mg/kg; menthol at 200 to 800 mg/kg a day enlarged the liver and vacuolated liver cells.

Human doses studied. EU well-established oral dose: 0.2 to 0.4 ml of oil in gastro-resistant capsules, 0.6 to 1.2 ml a day, up to 3 months per course; 0.2 ml three times a day for ages 8 to 11. IBS trials used 180 to 200 mg enteric-coated oil per capsule. A felodipine interaction study used a single 600 mg dose. Leaf tea: 1.5 to 3.0 g in 100 to 150 ml three times a day.

High dose or long term signals. No human long-term safety study was found. The EU limit for pulegone plus menthofuran is 37.5 mg a day for an adult for lifelong exposure, and 75 mg a day for under a year in the public statement quoted in the assessment report (50 kg adult).

Overdose response. EU oil monograph: severe gut symptoms, diarrhoea, rectal ulceration, seizures, loss of consciousness, apnoea, heart rhythm disturbance, ataxia; stomach emptying and symptomatic treatment advised. A near-fatal suicidal ingestion (coma, shock, ventilated, conscious by 24 hours, amount not stated) is cited in the assessment report but we did not read it. A 9-year-old boy had tachycardia and agitation after an infusion made with 30 leaves of a mint described as a carvone mint (likely not peppermint). Intravenous peppermint oil caused life-threatening lung injury in one 18-year-old.

Genotoxicity. EU: peppermint oil negative in two in vitro genotoxicity tests (Ames, mouse lymphoma) and in an animal comet/micronucleus test in female rats; pulegone and menthofuran are considered non-genotoxic carcinogens.

Toxic plant parts. Peppermint leaf tea: the EU leaf monograph reports no overdose cases. Essential oil: the concentrated part, source of menthol and pulegone. We found no source describing other peppermint plant parts as toxic. Do not confuse with pennyroyal (Mentha pulegium), whose oil is far richer in pulegone and has caused fatal poisoning.

Adulteration of peppermint oil is common in the two surveys we read, and pyrrolizidine alkaloids have been found in herbal teas including peppermint. No heavy-metal or pesticide survey specific to peppermint capsules was verified.

Adulterated peppermint essential oil. Of 36 commercial products labelled as containing peppermint oil, 53% did not meet the ISO specification. In a second analysis of 50 commercial peppermint oils, 42% were adulterated, with synthetic chemicals, de-mentholised cornmint oil and cheaper oils found. These are mostly essential oils; supplement capsules were not tested. The second study was funded in part by doTERRA, an essential oil seller, and the USDA. ^{145 151}

Pyrrolizidine alkaloids in teas. Peppermint tea was among ten naturally contaminated teas in a survey where pyrrolizidine alkaloid totals ran 154 to 2412 ng/g and 38 to 100% passed into the brew. A Turkish market survey found alkaloids in all tested herbal teas and herbs, including peppermint, with totals of 4.6 to 1054.5 ng/g in the listed group. Neither abstract gives a peppermint-only figure, and neither says how common contamination is. ^{115 41}

Pulegone and menthofuran content. Content varies by oil; the EU requires manufacturers to specify the amount in each product and keep the daily intake under 37.5 mg for adults. ^{29 31}

Variable supplement content. LactMed notes supplements may differ from labels and that results from one product may not apply to others. ¹

Body	Action	Date
European Medicines Agency, Committee on Herbal Medicinal Products (HMPC) (European Union)	Herbal monograph on Mentha x piperita L., aetheroleum (peppermint oil), Revision 1, adopted 15 January 2020. Well-established use: gastro-resistant oral forms for minor gut spasm, wind and pain especially in IBS; 10% on forehead and temples for mild tension headache. Traditional uses: cough and cold (inhalation, mouth, skin), localised muscle pain and itch on intact skin. Contraindications include allergy; oral gut use: liver disease, cholangitis, achlorhydria, gallstones, bile-duct disorders; traditional uses: under 2 years (reflex apnoea, laryngospasm) and seizure history. Pregnancy and lactation not recommended. Pulegone plus menthofuran under 37.5 mg a day per adult. Acid-lowering medicines and antacids to be avoided with oral capsules. source	2020-01-15
European Medicines Agency, Committee on Herbal Medicinal Products (HMPC) (European Union)	Herbal monograph on Mentha x piperita L., folium (peppermint leaf), Revision 1, adopted 15 January 2020. Traditional use of tea for indigestion and wind. Contraindicated with allergy to leaf or menthol. People with reflux should avoid it; caution with gallstones or bile-duct disorders; not recommended under 4; pregnancy and lactation not recommended; no interactions or overdose reported. source	2020-01-15
European Medicines Agency, Committee on Herbal Medicinal Products (HMPC) (European Union)	Assessment report on peppermint leaf and oil (EMA/HMPC/522409/2013, Revision 1). Source of the safety discussion on reflux, allergy, infants, G6PD, interactions, overdose and the pulegone and menthofuran limit derived from a 3-month rat study. source	2020
NIH National Center for Complementary and Integrative Health (NCCIH) (United States)	Peppermint oil appears safe orally or on the skin at commonly used doses; side effects heartburn, nausea, abdominal pain, dry mouth; allergic reactions rare; do not apply to the face of infants or young children; little known for medicinal amounts in pregnancy and breastfeeding; no interactions listed. source	Last updated May 2025
NIH LactMed (Drugs and Lactation Database) (United States)	Menthol and 1,8-cineole pass into breast milk in small amounts; large doses can cause heartburn, nausea and vomiting; topical use on nipples should be after nursing and wiped off before the next feed; peppermint has been used to suppress milk production. source	2026-10-15

When to get medical help

A baby or young child who coughs, chokes, goes pale or blue, or stops breathing after menthol or peppermint was put near the face or nose: call emergency services now and move the baby into fresh air.
Swelling of the lips, face or throat, trouble breathing, widespread hives or fainting after peppermint, menthol, toothpaste or mouthwash: emergency care.
Anyone who has swallowed bottled peppermint oil, a large amount of menthol, or any pennyroyal oil, with vomiting, drowsiness, confusion, fits or trouble breathing: emergency services or poison control at once; do not induce vomiting.
Chest pain, black or bloody stools, vomiting blood or food sticking when swallowing: see a doctor urgently; do not assume it is peppermint heartburn.
Yellow skin or eyes, dark urine or severe stomach pain after a peppermint oil product: stop it and see a doctor the same day.
A newborn who looks yellow (jaundiced) after menthol or camphor products near the cord or skin: see a doctor the same day, especially if G6PD deficiency runs in the family.
If you take warfarin: unexpected change in INR after starting menthol lozenges or peppermint oil; contact your clinic.
Transplant patients: any change in drug levels or signs of rejection after starting peppermint oil: contact the transplant team.

Stop the supplement and contact a clinician or emergency service. In the US, Poison Control is 1-800-222-1222.

General information only, not medical advice. Ask a clinician or pharmacist before use, especially with medicines, in pregnancy or with a health condition. See the Natural Remedy Safety guide.

Frequently asked questions

Does peppermint oil help irritable bowel syndrome?

It might help some adults, but the evidence is mixed. Older trials and pooled reviews favour enteric-coated oil for pain and overall symptoms, but the review authors rate the quality very low. The largest recent trials, in 2020 and 2021, did not beat placebo on their main goals, and side effects such as heartburn are more common than with placebo. Talk to a doctor first, because IBS symptoms should be properly diagnosed.

^{58 8 148 103}

Is peppermint tea as good as the capsules?

There is no evidence that it is. The IBS and indigestion trials tested oil capsules, not tea. Tea has far less oil and no coating. The EU lists tea as a traditional remedy for indigestion and wind, based on long use only, with no trial proof. If you try tea, 1.5 to 3 g of leaf in a cup, up to three times a day, is the EU traditional amount.

^{30 32 31}

Can peppermint cause or worsen heartburn?

Yes. Peppermint relaxes the valve between the food pipe and the stomach, so acid can rise more easily. The EU advises people with reflux to avoid peppermint leaf, and says people with heartburn or a hiatal hernia may get worse from the oil. Heartburn is a commonly reported effect of the capsules even with coating. Stop it if heartburn appears, and see a doctor about chest pain.

^{30 29 102 39}

Does peppermint oil help headaches?

A 10% oil solution rubbed on the forehead and temples eased tension headache about as well as 1,000 mg of paracetamol in one small 1996 trial of 41 adults. That is the best evidence, and it is thin, old and from one group. For migraine and for teenagers' headaches the evidence is very weak or shows no benefit. Do not use it on children under 18.

^{43 42 29}

Does peppermint help with nausea?

Smelling peppermint oil may lower nausea a little after surgery or with chemotherapy, but the evidence is low certainty, trials are small, and one found that slow breathing alone helped as much. In pregnancy, three small trials disagreed. Ask your midwife or doctor before using it in pregnancy.

^{144 134 54 25 61}

How much peppermint oil should I take?

There is no single right amount. The IBS trials used coated capsules of about 180 to 182 mg, two or three times a day, for 4 to 8 weeks. The EU well-established dose is 0.2 to 0.4 ml of oil per coated capsule, up to three times a day, 30 minutes before meals, for up to 3 months a course. The indigestion trials used one 90 mg peppermint and 50 mg caraway capsule twice a day for 4 weeks. Follow the label and do not swallow bottled essential oil.

^{148 103 81 29 27}

Is peppermint safe for babies and children?

Not near a baby's face. The EU contraindicates inhaled, mouth and skin peppermint oil and menthol under 2 years because menthol can cause reflex breathing stops and laryngospasm, and NIH says never to put it on the face of infants or young children. Oil capsules are not recommended under 8, and tea not under 4. A 2026 trial found no benefit for children's belly pain. If a baby coughs, goes pale or stops breathing after menthol, call emergency services.

^{29 102 31 119 141}

Can I take peppermint in pregnancy or while breastfeeding?

Food amounts are thought to be fine, but medicinal amounts are a question for your midwife or doctor. The EU does not recommend medicinal use of peppermint oil or leaf in pregnancy or breastfeeding because safety has not been established, while NIH says food amounts are likely safe. LactMed notes peppermint has been used to reduce milk supply, and advises applying it to nipples only after nursing and wiping it off before the next feed.

^{29 30 102 1}

Does peppermint interact with medicines?

Possibly, but the evidence is weak. In 12 healthy volunteers, 600 mg of peppermint oil raised the blood pressure drug felodipine to about 140% of normal exposure, with a wide range from 77% to 262%. In rats it raised cyclosporine levels. Two case reports link menthol cough drops with a lower warfarin INR. Acid reducers and antacids can dissolve the capsule coating early. Ask your pharmacist if you take any of these.

^{24 143 64 21 29}

Why does enteric coating matter?

The coating keeps the capsule closed in the stomach so the oil is released lower down, which reduces heartburn and may help it reach the bowel. Chewing or breaking a capsule, taking it with antacids, or taking acid-lowering medicine can open it too early. In a 16-man study coated capsules gave the same total menthol but peaked later (3.0 versus 1.7 hours).

^{29 31 84}

What is the difference between peppermint and spearmint, and what is pennyroyal?

Spearmint (Mentha spicata) is one parent of peppermint, and its oil is a different type: the IBS and headache evidence is for peppermint oil only. Pennyroyal (Mentha pulegium) is a different mint whose oil is rich in pulegone, which is toxic to the liver. A case series reported one death in four pennyroyal ingestions. Peppermint contains far less, and the EU caps the daily intake. Check the Latin name on any label and avoid pennyroyal products.

^{153 9 31 28}

Is peppermint safe to use long term?

Tea in normal amounts is generally regarded as safe, and the EU assessment reports no serious problems with prolonged tea use, but there is no long-term human safety study of the oil. The EU limits oil capsules to up to 3 months a course and caps pulegone and menthofuran at 37.5 mg a day for adults. No case of peppermint liver injury was found in our searches, but absence of reports is not proof of safety. Avoid it long term if you have reflux, gallstones or liver disease.

^{29 31 138 28}

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Editorial transparency

Written by: AlternativeMed editorial team. Research compiled with AI assistance, then checked against PubMed records.
Medical review: None. This page has not been reviewed by a physician or pharmacist.
First published: 2026-10-24
Last substantive update: 2026-10-24
How we research: We searched PubMed, NIH NCCIH, NIH LactMed, the EU herbal monographs and assessment report and other sources, opened each source and recorded the study design, people, product, dose and result as reported. Most studies were read as abstracts only; the EU monographs and assessment reports were read in full (the oil dosing was also seen in a 2007 draft). The NIH NCCIH page was read through a summarising tool. The NIH LiverTox, German Commission E and WHO entries could not be read directly, and nothing is claimed about them beyond what is marked. Early history rests on the EU assessment report and is marked as not checked in the originals. No study is cited that we could not verify.
How we rate evidence: See "How we rate evidence" in the Evidence tab.
Independence: No product is promoted on this page. No affiliate links are shown. If one is added later it will be labelled and kept apart from the evidence.

Sources 157

Each source was opened and checked. Where we read only the abstract, it says so. The small numbers in the text point here.

. Peppermint.. . 2006. PMID 30000911. (full-text)
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Ahn JH, Kim M, Kim RW. Effects of aromatherapy on nausea and vomiting in patients with cancer: A systematic review and meta-analysis of randomized controlled trials.. Complement Ther Clin Pract. 2024. PMID 38330531. DOI 10.1016/j.ctcp.2024.101838. (abstract)
Akbari SA, Alamolhoda SH, Baghban AA, et al.. Effects of menthol essence and breast milk on the improvement of nipple fissures in breastfeeding women.. J Res Med Sci. 2014. PMID 25364362. (abstract)
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