Inhalation Aromatherapy: How Scent Is Delivered and What Trials Used
How scent is delivered in inhalation aromatherapy, what trials and reviews found for nausea, anxiety, sleep and pain, why results are hard to compare, and the cautions.
Content last updated . This page has not been medically reviewed.
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Quick answer
Inhalation aromatherapy means breathing in the scent of an essential oil. Reviews of small trials report some short-term benefits for nausea, anxiety and sleep in specific groups of patients, but the studies are varied and often low in quality. This page describes what trials did. It is not a guide to using oils, and it does not say any oil treats or prevents a disease.
How scent is delivered in studies and practice
The National Cancer Institute (NCI) describes two kinds. In indirect inhalation, the patient breathes in an essential oil by using a room diffuser, or by drops placed on a tissue or cotton nearby. In direct inhalation, the patient uses an individual inhaler made by floating essential oil drops on hot water. [1] NIH says essential oils are most often used by inhaling them or by applying a diluted form to the skin. [2] Diffusers are covered on their own page.How the oil reaches the nose may matter. A systematic review of inhaled aromatherapy for chemotherapy nausea found benefit in seven of nine adult studies using direct or dry inhalation, while atmospheric diffusion and use in children did not show benefit. [3]
What trials and reviews found
These are research findings, not traditional use. The labels are ours.| Setting | What the source found | Evidence label | Population and form studied |
|---|---|---|---|
| Nausea during chemotherapy | A systematic review of 11 studies called results promising for direct inhalation, but noted small samples and a wide variety of oils and methods. [3] NIH summarizes a 2024 review that found inhaled peppermint oil particularly successful at reducing nausea and vomiting. [4] | Promising but limited | Mostly women with gynecologic cancers (earlier review); inhaled |
| Anxiety and depression in cancer | A 2022 meta-analysis found lower anxiety and depression scores, but study quality was low, and it concluded the literature does not yet support clinical implementation. [5] | Mixed | People with cancer; many compared with usual care |
| Anxiety during radiation therapy | In a trial of 313 patients randomly assigned to lavender, bergamot or cedarwood oils, no differences in depression or anxiety were reported between the groups. [1] | No difference found between oils | Patients having radiation therapy; inhaled |
| Needle procedures | A 2025 meta-analysis of 9 studies found less pain and anxiety with aromatherapy, and noted high heterogeneity and methodological limitations. [6] | Promising but limited | Adults having needle procedures; inhaled and topical were both included |
| Sleep | A 2025 meta-analysis of 27 publications found inhalation aromatherapy relieved symptoms of insomnia that came with other conditions. It also noted lack of blinding and heterogeneity. [7] NIH says little rigorous research has been done on aromatherapy for insomnia. [2] | Promising but limited | Adults with insomnia alongside other conditions |
| Children | A trial of 37 children and adolescents having stem cell infusions compared bergamot oil with a pleasant-smelling shampoo and found aromatherapy was not effective in reducing nausea, anxiety or pain. [1] | No benefit found in this trial | Children and adolescents; inhaled |
| Orange oil versus real orange | In adults at stem cell infusion, tasting or sniffing sliced oranges was more effective than inhaling orange essential oil. [1] | One small comparison | Adult patients |
Why the results are hard to compare
- Scent is hard to hide. Blinding is difficult, and a review of insomnia trials listed lack of blinding as a common problem. [7]
- Placebo effects. In the cancer anxiety review, placebo also appeared to be effective in some studies. [5]
- Different oils and methods. The chemotherapy nausea review found different oils, numbers of drops and methods of administration across studies. [3]
- Specific groups. Findings from patients having treatment do not transfer to healthy people, children, or home use.
For a longer look at how scent and the brain are studied, see how scent works.
Related pages
Aromatherapy overview, essential oil diffusers, lavender oil, peppermint oil and aromatherapy in hospitals.Frequently asked questions
What is inhalation aromatherapy?
It is breathing in the scent of an essential oil, for example from a diffuser, a tissue or an individual inhaler. [1]
Does smelling essential oils reduce anxiety?
Results are mixed. NIH says it is unclear whether lavender aromatherapy helps anxiety or stress. [8] A cancer-care meta-analysis found lower anxiety scores but low study quality. [5]
Does inhaling peppermint oil help nausea?
A 2024 review summarized by NIH found inhaled peppermint oil particularly successful in reducing nausea and vomiting in patients with cancer having chemotherapy. [4] The studies were small, so treat this as promising but limited.
Is a diffuser the same as an individual inhaler?
Not in the trials reviewed. A review of chemotherapy nausea studies found benefit with direct or dry inhalation but not with atmospheric diffusion. [3]
Can inhalation aromatherapy cause problems?
Yes. Headache or coughing can occur with lavender, and fragranced products are reported to trigger symptoms in many people with asthma. [8] [9]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Proper evidence not found
We looked for sources describing a safe, standard "amount of inhaled oil" or "minutes of inhalation" that applies to everyone. Proper evidence not found in the NIH, NCI, Poison Control and review sources we read. Trials differ, and we do not give a schedule.
Safety and who should ask first
- Headache or cough. NIH says aromatherapy with lavender oil is considered possibly safe but may cause headache or coughing. [8]
- Peppermint and young children. NIH says peppermint oil should not be applied to the face of infants or young children because serious side effects may occur if they inhale the menthol, and that menthol should not be inhaled by an infant or small child. [4]
- Asthma and sensitive airways. A 2018 survey of adults in the US (self-reported, not specific to essential oils) found 64.3% of asthmatics reported adverse health effects from fragranced products. [9] See asthma and breathing problems.
- Hormone-related questions. NIEHS says the clinical cases of breast tissue growth in boys involved skin use, not aromatherapy, and more studies are needed to know about aromatherapy. [10]
- Pregnancy and breastfeeding. NIH says little is known about whether lavender is safe in pregnancy or breastfeeding. [8] See pregnancy and breastfeeding.
- Never swallow oils. Poison Control warns that misuse of essential oils can cause serious poisoning, and that aspirating an essential oil can cause pneumonia. [11] Poison Help (US): 1-800-222-1222. Call 911 for collapse, seizure or trouble breathing.
- Ask a pharmacist or clinician if you take medicines or have a lung, heart or neurological condition. See medication interactions.
References
- Aromatherapy With Essential Oils (PDQ), Patient Version, National Cancer Institute. Read 2026-10-23.
- Aromatherapy, NCCIH (NIH), last updated January 2020. Read 2026-10-23.
- Effectiveness of Inhaled Aromatherapy on Chemotherapy-Induced Nausea and Vomiting: A Systematic Review, Toniolo J et al., J Altern Complement Med 2021, PMID 34283916. Read 2026-10-23.
- Peppermint Oil: Usefulness and Safety, NCCIH (NIH). Read 2026-10-23.
- Aromatherapy with inhalation can effectively improve the anxiety and depression of cancer patients: A meta-analysis, Liu T et al., Gen Hosp Psychiatry 2022, PMID 35617792. Read 2026-10-23.
- The Efficacy of Aromatherapy on Pain and Anxiety During Needle-Related Procedures in Adults: A Systematic Review and Meta-Analysis, Sun C et al., J Pain Res 2025, PMID 40827258. Read 2026-10-23.
- Inhalation aromatherapy for the treatment of comorbid insomnia: a systematic review and meta-analysis, Chen HB et al., Front Psychiatry 2025, PMID 40230824. Read 2026-10-23.
- Lavender: Usefulness and Safety, NCCIH (NIH). Read 2026-10-23.
- Fragranced consumer products: effects on asthmatics, Steinemann A, Air Qual Atmos Health 2018, PMID 29391919. Read 2026-10-23.
- Essential Oils, National Institute of Environmental Health Sciences (NIH), last reviewed March 19, 2026. Read 2026-10-23.
- Essential oils: Poisonous when misused, Poison Control. Read 2026-10-23.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.