Butterbur Extract (PA-Free): Migraine, Sinus & Allergy…

Butterbur for migraine and hay fever: what the trials show

Butterbur extract comes from Petasites hybridus leaves or rhizomes. Its main active constituents are petasins such as isopetasin. The better products are sold as CO₂ extracts with the pyrrolizidine alkaloids (PAs) removed, because PAs are known to be toxic to the liver. Removal is not a guarantee: liver injury has been reported with extracts where small amounts of alkaloids remained (Medsafe, 2012). Teas, tinctures and powders are not safe choices.

How it might work is not settled. The mechanism of the anti-migraine action is unknown. In lab work, isopetasin activates the TRPA1 pain channel on nerve cells and makes them less responsive, which may be part of the explanation (Benemei 2017).

Takeaway: the evidence is one adult migraine trial and one short hay-fever trial. Think of butterbur as a preventive option to discuss with a clinician, not as instant relief for an active migraine.

What the research found

Migraine prevention (adults). In one randomized, placebo-controlled trial of 245 adults over four months, butterbur root extract 75 mg twice daily cut monthly migraine attacks by 48%, versus 26% with placebo. The 50 mg twice-daily dose (36% fewer attacks) did not beat placebo. The benefit was already significant at months 1, 2 and 3 on the responder measure (Lipton 2004).
Children and teens. One open-label study of 108 children and teens (4 months, no control group) reported a 63% fall in attacks, with doses set by age (50–150 mg a day) (Pothmann 2005). The only randomized pediatric trial we checked (n=58) found butterbur better than placebo only at the 6-month follow-up (Oelkers-Ax 2008). Pediatric use should be clinician-guided.
Hay fever (allergic rhinitis). In one 2-week trial of 125 adults, butterbur (ZE 339) and cetirizine gave similar overall improvement. About two thirds of the reported side effects in the cetirizine group were drowsiness or fatigue. Sneezing, itch and congestion were not reported separately (Schapowal 2002). A 2025 review of the same extract was written mostly by staff of its manufacturer (Merk 2025).
Tolerability. The most common side effects in the trials were belching and mild stomach upset (Lipton 2004; Pothmann 2005).

What to buy and avoid

Choose a PA-free, CO₂-extracted butterbur extract from a brand that publishes a batch certificate of analysis (COA) showing pyrrolizidine alkaloids as not detected. See the glossary entry on a COA.
Avoid teas, tinctures and powders, and anything that does not state PA-free.

Doses used in the trials

Migraine prevention (adults): 75 mg twice daily was the dose that beat placebo over four months. 50 mg twice daily did not.
Hay fever: the trial used one tablet of ZE 339 four times a day for 2 weeks. Check the label of any product against that; do not guess a dose from petasin content.
The trials did not test maintenance or once-daily dosing, so there is no sourced dose for either.

Safety and who should avoid it

The liver is the main target of PAs, which are known to be hepatotoxic in humans. Liver disease is a reason to avoid butterbur; ask a clinician first.
A 2025 review links dietary PA exposure to pulmonary arterial hypertension. A lung effect of butterbur itself is not established (Zhang 2025).
The trials above did not study pregnancy or breastfeeding, so they give no safety data for either. Talk to a clinician before use.
Butterbur belongs to the Asteraceae (daisy) family, the same plant family as ragweed.
A 2019 review calls butterbur effective for migraine "with potential risks of hepatotoxicity related to preparation" (Rajapakse 2019).

Sources

Lipton RB et al. Petasites hybridus root (butterbur) is an effective preventive treatment for migraine. Neurology 2004. PubMed 15623680
Schapowal A. Randomised controlled trial of butterbur and cetirizine for treating seasonal allergic rhinitis. BMJ 2002. PubMed 11799030
Pothmann R, Danesch U. Migraine prevention in children and adolescents: an open study with a special butterbur root extract. Headache 2005. PubMed 15836592
Oelkers-Ax R et al. Butterbur root extract and music therapy in the prevention of childhood migraine. Eur J Pain 2008. PubMed 17659990
Benemei S et al. The anti-migraine component of butterbur extracts, isopetasin, desensitizes peptidergic nociceptors by acting on TRPA1. Br J Pharmacol 2017. PubMed 28622417
Medsafe (New Zealand). Butterbur and liver toxicity, June 2012.
Rajapakse T, Davenport WJ. Phytomedicines in the Treatment of Migraine. CNS Drugs 2019. PubMed 30627973
Zhang C et al. The underexplored pulmonary toxicity of pyrrolizidine alkaloids. Chem Biol Interact 2025. PubMed 40848869
Merk VM et al. Efficacy and Safety of P. hybridus Leaf Extract Ze 339 for Allergic Rhinitis. Adv Respir Med 2025. PubMed 40558112

This article is general information, not medical advice. Talk to a clinician before using butterbur, especially if you have liver disease or take other medicines.