Butterbur (Petasites hybridus): Uses, Evidence and Safety

Safety first: liver and cancer risk. The butterbur plant contains pyrrolizidine alkaloids (PAs), which the US National Center for Complementary and Integrative Health (NCCIH) says can damage the liver and lungs and may cause cancer. [1] NCCIH says only products processed to remove PAs and labeled or certified as PA-free should be considered. [1] Even then, it reports rare cases of liver injury with products reported to be PA-free. [1] The UK Medicines and Healthcare products Regulatory Agency (MHRA) said in 2021 that its earlier advice not to take unlicensed butterbur herbal remedies remained unchanged. [2] For warning signs such as yellow skin or eyes, dark urine or severe tiredness, see liver injury warning signs and seek care.

Overview

NCCIH describes butterbur as a shrub that grows in Europe and parts of Asia and North America; the name is attributed to the traditional use of its large leaves to wrap butter. [1] It is promoted as a supplement for migraine and hay fever (allergic rhinitis). [1] Some of the best-known migraine research is also some of the most worrying on safety, so this page covers both. For the wider picture see herbs for headache and migraine. The same alkaloid family is covered in pyrrolizidine alkaloids: comfrey, coltsfoot and borage.

Names, plant part and look-alike traps

The accepted name is Petasites hybridus (L.) G.Gaertn., B.Mey. & Scherb., in the daisy family (Asteraceae). [3] NCCIH lists Petasites officinalis and Tussilago hybrida as other names. [1] The plant parts matter: NCCIH describes a root extract studied for migraine and a leaf extract studied for hay fever. [1] Petasites is a genus with several species, covered together in a 2022 review, so a result for one species or part does not carry over to another. [4] We give no identification or foraging advice; for any plant eaten by mistake, see plant and mushroom poisoning and call Poison Help at 1-800-222-1222 (US).

Traditional use (not proof)

NCCIH notes that butterbur has been used for health purposes for many centuries, and that in the Middle Ages the odor and smoke of burning roots were thought to fight plague. [1] A 2022 review says species of Petasites have been used in the traditional medicine of Asian and European countries for conditions including migraine, asthma and allergic rhinitis. [4] Tradition does not show that a use is safe or effective.

What research shows

A 2025 review of headache supplements summarizes butterbur as having "strong evidence for efficacy and concern for hepatotoxicity." [8] How to weigh a possible benefit against a rare but serious liver risk is a decision for a headache clinician.

Forms and why the form matters

The migraine research used special extracts made to remove PAs. [1] Raw plant, teas, tinctures and products that are not labeled PA-free are a different matter; NCCIH warns that products with PAs may not be safe on the skin because PAs could be absorbed through cuts or scrapes. [1] We give no preparation instructions. See herb forms and preparations.

Safety

• Liver. A 2019 review of safety reports for one standardized root extract counted 60 liver-related reports, with most showing mild blood-test changes. [9] Nine developed severe injury, and two needed liver transplants; the authors described the cases as rare, idiosyncratic and often confounded by other medicines. [9] That review used safety reports supplied by the manufacturer, so read it as one view alongside NCCIH and MHRA. [9]
• Medicines. NCCIH advises talking with a health care provider about any medicine because some herbs and medicines interact in harmful ways. [1] In that review, 22 patients reported taking other medicines known to harm the liver. [9] See how interactions work.
• Pregnancy and breastfeeding. NCCIH says products with PAs should not be used because they may cause birth defects or liver damage, and little is known about PA-free products. [1] See pregnancy and breastfeeding.
• Children. NCCIH notes studies in children and adolescents reported PA-free products seemed safe for up to 16 weeks, with rare liver injury still possible. [1] Ask a pediatric clinician; see children and teens.
• Allergy. NCCIH says butterbur may cause an allergic reaction in people allergic to related plants, such as ragweed, chrysanthemums, marigolds and daisies. [1] See herbal allergy and cross-reactivity.
• Common side effects. Belching, diarrhea, drowsiness, rash and stomach upset. [1]
• Kidney, bleeding, surgery. Not described in the sources we read; tell the surgical team about every supplement.

Quality

Whether a product is truly PA-free is the central quality question, and a label alone may not settle it. See product quality and contamination and quality testing and certifications.

Official statements

• American Academy of Neurology and American Headache Society (US), 2012: butterbur "should be offered" for migraine prevention (Level A). [6] NCCIH reports the Academy stopped recommending it in 2015 over safety. [1]
• MHRA (UK), 2021: butterbur contains PAs that can cause serious adverse effects such as liver damage and organ failure, and advice not to take unlicensed butterbur herbal remedies remains unchanged. [2]
• NCCIH (US), last updated November 2024: only PA-free labeled or certified products should be considered. [1]