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Butterbur

In adults with migraine, a root extract at 75 mg twice a day cut attacks by 48% against 26% on placebo, and a lower dose did not differ from placebo. Leaf extract matched antihistamines for hay fever in trials. Spontaneous reports describe liver injury, including two liver transplants. EMA notes the Petasites genus contains liver-toxic pyrrolizidine alkaloids.

Add to Bio HackChecked 2026-11-09
Status
Dietary supplement in the US. Not approved by the FDA as a drug for any use.
Also called
Petasites hybridus, Petasites, petasin, Petadolex, Ze 339, Tesalin, butterbur root extract, butterbur leaf extract, pestilence wort, bog rhubarb
Taken for
migraine prevention, headaches, hay fever, allergic rhinitis, allergies, asthma, inflammation

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help3

Reported risks3

What people take it for, and what was found

Shown to help3

Moderate

Migraine prevention

Shown to cut migraine attacks by 48% against 26% on placebo at 75 mg twice a day in adults. The lower dose did not differ from placebo.

The numbers and sources
Effect
In 245 adults over 4 months, migraine attack frequency fell by 48% on Petasites root extract 75 mg twice a day (p 0.0012 against placebo), 36% on 50 mg twice a day (p 0.127) and 26% on placebo. 68% on 75 mg twice a day and 49% on placebo had at least a 50% drop in attacks (p < 0.05) [1]. A systematic review of two Petadolex trials (293 patients) found fewer attacks and more responders at 150 mg a day than at 100 mg a day or on placebo over 3 to 4 months, and did not pool them because results differed [2]. In 58 primary school children, butterbur root extract did not differ from placebo right after 12 weeks of treatment and had fewer headaches than placebo 6 months later (p 0.044) [3].
Population
Adults aged 18 to 65 with 2 to 6 migraine attacks a month [1]. Adults in two RCTs [2]. Children with migraine [3].
Sources
[1], [2], [3]
Caveats
The two trials in the review include the 245-patient trial [1][2]. The children's trial analyzed completers, and all groups improved during the baseline period [3].
Moderate

Hay fever

Shown to ease hay fever symptoms more than placebo in adults, about as much as fexofenadine or cetirizine.

The numbers and sources
Effect
In 330 patients with intermittent allergic rhinitis, butterbur leaf extract Ze 339 three times a day and fexofenadine each improved daytime symptoms more than placebo (p < 0.001), with no difference between them (p 0.37) [4]. In 125 patients over 2 weeks, Ze 339 four times a day and cetirizine gave similar SF-36 and clinical global impression scores [5]. A meta-analysis of single medicinal plants, in which Petasites was the most studied, found total nasal symptoms improved against placebo (SMD -0.31, 95% CI -0.59 to -0.02, 5 studies, 249 participants) and no clear difference from antihistamines [6]. A systematic review of 11 phytotherapy studies found Petasites the most studied plant, with effects on symptoms, nasal airflow and immune markers [7].
Population
Adults with seasonal or intermittent allergic rhinitis in Switzerland and Germany [4][5]. Adults and children in RCTs [6][7].
Sources
[4], [5], [6], [7]
Caveats
The meta-analysis pooled several plants and rated the evidence very low to low certainty against placebo [6]. The cetirizine trial had no placebo arm [5].
Limited

Asthma

One small trial found 1 week of butterbur improved airway and blood markers in 16 adults with asthma on inhaled steroids. Attacks were not measured.

The numbers and sources
Effect
In 16 atopic asthma patients on inhaled corticosteroids, butterbur 25 mg twice a day for 1 week improved airway response to an AMP challenge by 0.7 doubling doses against placebo (P < 0.05), and lowered exhaled nitric oxide, serum eosinophil cationic protein and blood eosinophils [8].
Population
16 adults, crossover design [8].
Sources
[8]
Caveats
One week of treatment in 16 people. The outcomes were airway and blood markers, not attacks or symptoms [8].

Doses studied

The adult migraine trial used root extract 75 mg or 50 mg twice a day for 4 months [1], and the review describes 150 mg a day against 100 mg a day [2]. The hay fever trials used Ze 339 leaf extract with 8 mg total petasine three times a day [4], or one tablet four times a day for 2 weeks [5]. The asthma trial used 25 mg twice a day for 1 week [8]. Liver injury reports involved 50 to 225 mg a day [9].

Risks

Reported risks3

Limited

Liver injury

Case reports: liver injury was reported with Petadolex, including nine severe cases and two transplants. Many patients also took other liver-toxic medicines.

The numbers and sources
Effect
Spontaneous reports describe herb-induced liver injury with Petadolex. Most patients had mild changes below 3 times the upper limit of normal, at 50 to 225 mg a day for 4 to 730 days. Nine had severe injury, with onset at an average of 103 days. Two needed liver transplants. Causality was rated likely in 3 cases, possible in 13, unlikely in 8 and unclassifiable in 24. 22 patients reported other liver-toxic medicines [9].
Population
Spontaneous case reports [9].
Sources
[9]
Caveats
Case reports give no rate, and many cases were confounded by other medicines [9].
Limited

Pyrrolizidine alkaloids

The EMA herbal committee lists Petasites among plants with pyrrolizidine alkaloids, linked to liver vein blockage and lung hypertension, and sets an adult limit of 1 µg a day.

The numbers and sources
Effect
The European Medicines Agency's herbal committee lists Petasites among plant genera with long-known pyrrolizidine alkaloid content. It describes these alkaloids causing hepatic veno-occlusive disease and pulmonary arterial hypertension, and notes animal carcinogenicity findings for Petasites japonicum extracts. It set an acceptable intake of 1.0 µg a day for adults from herbal medicinal products [10].
Population
Regulatory review of human poisonings and animal studies [10].
Sources
[10]
Caveats
The statement concerns the plant genus and the alkaloid class. It did not test specific butterbur products. The carcinogenicity findings are from animals [10].
Moderate

Side effects in trials

Side effects were mild in trials, mainly burping in the migraine trial. These trials were too short and small to detect rare liver injury.

The numbers and sources
Effect
In the 245-patient migraine trial, the most frequent possibly related adverse reactions were mild digestive events, mainly burping [1]. Both hay fever trials reported the treatments as well tolerated [4][5]. Medicinal plants for allergic rhinitis appeared well tolerated up to 8 weeks [6].
Population
Migraine and hay fever trial participants [1][4][5][6].
Sources
[1], [4], [5], [6]
Caveats
Trials lasted weeks to months, too short and small to detect rare liver injury.

Claims tested and not found

  1. That a lower butterbur dose prevents migraine. Attack frequency on 50 mg twice a day did not differ from placebo (p 0.127) [1].

Sources

  1. Lipton RB, Göbel H, Einhäupl KM, et al. Petasites hybridus root (butterbur) is an effective preventive treatment for migraine. Neurology. 2004. https://doi.org/10.1212/01.wnl.0000147290.68260.11
  2. Agosti R, Duke RK, Chrubasik JE, Chrubasik S. Effectiveness of Petasites hybridus preparations in the prophylaxis of migraine: a systematic review. Phytomedicine. 2006. https://doi.org/10.1016/j.phymed.2006.02.008
  3. Oelkers-Ax R, Leins A, Parzer P, et al. Butterbur root extract and music therapy in the prevention of childhood migraine: an explorative study. European Journal of Pain. 2008. https://doi.org/10.1016/j.ejpain.2007.06.003
  4. Schapowal A, Study Group. Treating intermittent allergic rhinitis: a prospective, randomized, placebo and antihistamine-controlled study of Butterbur extract Ze 339. Phytotherapy Research. 2005. https://doi.org/10.1002/ptr.1705
  5. Schapowal A. Randomised controlled trial of butterbur and cetirizine for treating seasonal allergic rhinitis. BMJ. 2002. https://doi.org/10.1136/bmj.324.7330.144
  6. Lim XY, Lau MS, Zolkifli NA, et al. Medicinal plants for allergic rhinitis: A systematic review and meta-analysis. PLOS ONE. 2024. https://doi.org/10.1371/journal.pone.0297839
  7. Braunwalder C, Ertl J, Wullschleger M, et al. Efficacy and Safety of Phytotherapy and Anthroposophic Medicine in Seasonal Allergic Rhinitis: A Systematic Review. International Archives of Allergy and Immunology. 2024. https://doi.org/10.1159/000539645
  8. Lee DKC, Haggart K, Robb FM, Lipworth BJ. Butterbur, a herbal remedy, confers complementary anti-inflammatory activity in asthmatic patients receiving inhaled corticosteroids. Clinical & Experimental Allergy. 2004. https://doi.org/10.1111/j.1365-2222.2004.01838.x
  9. Anderson N, Borlak J. Hepatobiliary Events in Migraine Therapy with Herbs: The Case of Petadolex, A Petasites Hybridus Extract. Journal of Clinical Medicine. 2019. https://doi.org/10.3390/jcm8050652
  10. European Medicines Agency, Committee on Herbal Medicinal Products. Public statement on the use of herbal medicinal products containing toxic, unsaturated pyrrolizidine alkaloids (PAs) including recommendations regarding contamination of herbal medicinal products with PAs. EMA/HMPC/893108/2011 Rev. 1. 2021. https://www.ema.europa.eu/en/documents/public-statement/public-statement-use-herbal-medicinal-products-containing-toxic-unsaturated-pyrrolizidine-alkaloids-pas-including-recommendations-regarding-contamination-herbal-medicinal-products-pyrrolizidine_en.pdf

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