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Butterbur (Petasites hybridus) is a large-leaved perennial in the aster family (Asteraceae), historically called names such as pestilence-wort, butter-dock, and purple butterbur. It has centuries of European herbal history and became widely known in modern herbal medicine because standardized extracts were studied for migraine prevention and allergic rhinitis. Butterbur also presents an unusually important quality-control issue: the raw plant naturally contains pyrrolizidine alkaloids (PAs) that can injure the liver and carry mutagenic and carcinogenic concerns.
Botanical Identity & Parts Used
Botanical name: Petasites hybridus (L.) G.Gaertn., B.Mey. & Scherb.
Family: Asteraceae
Historically used parts: root/rhizome and leaves.
Modern studied forms: standardized, processed extracts designed to remove pyrrolizidine alkaloids.
Kew Plants of the World Online recognizes Petasites hybridus as an accepted species native across much of Europe into northern Iran. It is a rhizomatous plant associated with moist ground, stream banks, and other damp habitats.
Identification
Butterbur produces thick flower stalks before its enormous leaves fully expand. Its broad, heart- to kidney-shaped leaves can become exceptionally large. The pinkish to lilac flower heads are borne in clustered spikes. Butterbur should not be confused with coltsfoot (Tussilago farfara), another Asteraceae herb that also has a PA-related safety history and shares some old common names.
History & Traditional Use
The name “butterbur” is associated with the old practice of wrapping butter in the plant’s large leaves during warm weather. Historical European herbal use included the root and leaves for cough, fever, spasms, pain, and other complaints. In medieval Europe, butterbur was also associated with plague remedies—an important historical tradition, but not evidence that the plant prevents or treats plague or modern infectious disease.
Traditional Preparation vs. Modern Extracts
Historical herbals describe root and leaf preparations, including infusions, decoctions, and other preparations. Modern safety knowledge changes how those historical practices should be interpreted. Because naturally occurring PAs can be present in both root and leaf, a homemade tea, tincture, powder, or extract made from ordinary raw P. hybridus cannot be assumed to be PA-free.
Modern human trials therefore do not justify treating raw butterbur like an ordinary kitchen herb. The best-studied products were manufactured extracts with controlled processing and specified petasin content. Older migraine trials commonly studied standardized extracts in amounts such as 50–75 mg twice daily for up to several months. Those figures describe specific research products, not an interchangeable dose for raw herb or unidentified supplements.
Key Constituents
Butterbur contains sesquiterpenes including petasin, isopetasin, and related compounds that have been studied for antispasmodic and inflammatory effects. The plant can also contain unsaturated pyrrolizidine alkaloids, including senecionine-related compounds. The therapeutic-interest compounds and toxic PAs are separate quality-control issues: a product can contain useful petasins while still requiring rigorous PA removal and testing.
Migraine Research
Several controlled trials investigated standardized butterbur root extracts for migraine prevention. A 2006 systematic review found moderate evidence that a particular higher-dose proprietary extract reduced migraine frequency compared with placebo, but also concluded that more rigorous work was needed, especially for long-term safety.
In 2012, an American Academy of Neurology/American Headache Society guideline recommended butterbur for migraine prevention; that guideline was later retired, and the Academy stopped recommending butterbur in 2015 because of safety concerns surrounding PA contamination and product quality. This history matters: it shows that evidence of potential benefit and concerns about real-world product safety can exist at the same time.
Allergic Rhinitis Research
Standardized butterbur leaf extracts have also been studied for seasonal allergic rhinitis. Some trials reported symptom improvement, but guidelines and expert groups have disagreed about how strong the evidence is and whether the safety tradeoff justifies use. Research on other proposed uses is much more limited.
Pyrrolizidine Alkaloids: The Central Safety Issue
Raw butterbur naturally contains pyrrolizidine alkaloids. These compounds can damage the liver and lungs, and some are genotoxic or carcinogenic. NCCIH states that only products processed to remove PAs and labeled or certified as PA-free should even be considered for use. Reported product testing has also found substantial variation between labels and measured constituents, so “PA-free” is a quality claim that depends on manufacturing and testing.
Rare liver-injury cases have been reported even with products described as PA-free, which means processing lowers a known risk but does not turn butterbur into a risk-free herb.
Safety & Contraindications
- Liver disease: concentrated butterbur use is inappropriate without professional review, and references advise avoiding use in hepatic impairment.
- Allergy: butterbur is in the Asteraceae family. People allergic to ragweed, chrysanthemums, daisies, marigolds, and related plants may react.
- Digestive effects: belching, nausea, stomach upset, diarrhea, and flatulence are among reported adverse effects.
- Drowsiness and dizziness: these have occurred in trials and postmarketing reports.
- Product quality: never assume raw plant material, home extracts, or an unverified supplement has had toxic PAs removed.
Pregnancy, Breastfeeding & Children
PA-containing butterbur should not be used during pregnancy or breastfeeding because of potential liver toxicity and developmental concerns. Safety data for PA-free products in pregnancy and lactation are still inadequate. Some pediatric migraine studies used standardized extracts, but that does not establish the safety of raw herb or arbitrary commercial products for children.
Medication & Surgery Considerations
Well-documented human drug interactions are limited, but butterbur’s liver-toxicity history and possible cardiovascular and enzyme effects make medication review important. People using prescription medicines, especially those with liver concerns or multiple medications, should disclose butterbur use before surgery or when changing treatment.
Sourcing & Quality
For this herb, sourcing is part of the safety profile. A responsible product should clearly identify Petasites hybridus, the plant part, extraction method, petasin standardization when relevant, and independent testing or certification for pyrrolizidine alkaloids. “Natural,” “traditional,” or “wildcrafted” does not answer the PA question.
Related Roosters Peacock Herb Guides
Coltsfoot (Tussilago farfara)
Borage (Borago officinalis)
Lungwort (Pulmonaria officinalis)
References
- National Center for Complementary and Integrative Health — Butterbur: Usefulness and Safety.
- Memorial Sloan Kettering Cancer Center — Butterbur.
- NIH LiverTox — Butterbur.
- Kew Science, Plants of the World Online — Petasites hybridus.
- Agosti R, et al. Effectiveness of Petasites hybridus preparations in the prophylaxis of migraine: a systematic review.
- Drugs.com Natural Products — Butterbur.
- Kulinowski Ł, et al. Review of the ethnobotany, phytochemistry, pharmacology and toxicology of butterbur species.
Last reviewed: September 26, 2026.
Roosters Peacock educational herb reference. Historical uses are preserved as part of herbal tradition while modern PA-related safety and product-quality findings are presented separately.