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Butterbur (Petasites hybridus)
A botanical with solid RCT evidence for migraine prophylaxis (75mg twice daily) and allergic rhinitis, but raw butterbur contains liver-toxic pyrrolizidine alkaloids. Avoid PA-containing or inadequately verified products, and know that even a PA-free label does not guarantee safety.
What the evidence says
Butterbur doesn't have enough studies with structured effect-size data yet to pool a verdict. Browse the studies below for individual findings.
Most evidence is from high-quality meta-analyses and randomised trials published 2002–2025 with a typical study size of 186 participants.
Based on 21 studies · 1 meta-analysis · 13 RCTs · 556 total participants
Confidence
Moderate confidenceBy outcome
Placebo-controlled RCTs show efficacy for migraine prophylaxis at 75 mg twice daily and for allergic rhinitis, while reviews rate the evidence moderate or limited. The trial base is small, and hepatotoxic pyrrolizidine-alkaloid safety concerns cap confidence.
10 randomised trials
100% were about Butterbur in an audit of 10 of them
Every randomised or controlled trial of Butterbur indexed in PubMed, not a hand-picked subset. Meta-analyses and systematic reviews are deliberately excluded from this count: most of them cover many compounds at once, so counting them would inflate it.
PubMed · as of Sep 2026
Butterbur (Petasites hybridus) has some of the stronger botanical evidence in its categories: a 245-patient RCT showed 75mg twice daily cut migraine frequency by 48% (vs 26% placebo), and for hay fever one 125-patient, two-week trial found no difference from cetirizine in quality-of-life or global improvement scores, while two thirds of the adverse events reported on cetirizine were drowsiness or fatigue.
A 2024 meta-analysis found no clear difference between herbal remedies and antihistamines, but only two trials were pooled, and it concluded clear evidence of benefit is still lacking. Its actives are petasin and isopetasin.
The critical caveat is safety: the raw plant contains pyrrolizidine alkaloids (PAs) that are hepatotoxic and carcinogenic, and rare liver-injury cases have been reported.
Only certified PA-free standardized extracts (e.g., Petadolex, Ze339) should be used, and even then liver monitoring is prudent — which is why professional guidelines have grown cautious despite the efficacy data.
Petasin and isopetasin inhibit leukotriene and inflammatory pathways and have antispasmodic/vasoregulatory effects relevant to migraine.
Dampens the allergic/histamine response, easing allergic-rhinitis symptoms.
Affects cerebral vascular tone, a proposed migraine-prophylaxis mechanism.
How Butterbur works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
Avoid entirely.
Avoid.
Only under specialist supervision with PA-free extract.
Additive liver-injury risk, especially with non-PA-free products.
Theoretical additive effects.
Pyrrolizidine alkaloids are bioactivated by CYP enzymes, another reason to avoid PA-containing products.
Tip: Take with food; most common reported effect
Tip: Use only certified PA-free extracts, which removes the alkaloid risk but not the rare reported liver injury. Stop and seek care if jaundice, dark urine or abdominal pain appear
Tip: Avoid if allergic to ragweed/daisies
Butterbur has an evidence score of 6/10 — moderate evidence based on 21 indexed studies, including 1 meta-analysis. A botanical with solid RCT evidence for migraine prophylaxis (75mg twice daily) and allergic rhinitis, but raw butterbur contains liver-toxic pyrrolizidine alkaloids. Avoid PA-containing or inadequately verified products, and know that even a PA-free label does not guarantee safety. Representative study: PMID 38603736.
The commonly studied dose of Butterbur is 50-75mg PA-free standardized extract twice daily for migraine prophylaxis (≈100-150mg/day); allergic rhinitis similar (in the cited migraine trial, 50 mg twice daily did not beat placebo and 75 mg twice daily did). Individual needs vary, so check the right dose for you with a healthcare provider.
The best time to take Butterbur is with meals. Take it with food. Taken with food, split into two daily doses; the 75mg-twice-daily migraine dose outperformed 50mg twice daily.
Butterbur should be used with caution — talk to a healthcare provider before taking it. Reported side effects include liver injury (PA-containing products, and rare reports with a PA-free extract), allergic reaction (Asteraceae), burping/GI upset. How often they occur is not established for all of them. Use caution if any of these apply to you: Liver disease; Pregnancy and breastfeeding; Allergy to ragweed/daisy family (Asteraceae).
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Reviewed by Dr. Baher Al Hakim · Last reviewed June 2026 · evidence from 21 studies · how we score · editorial policy
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
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