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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, so ONLY certified PA-free extracts should ever be used.
What the evidence says
Most Butterbur studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from high-quality meta-analyses and randomised trials published 2002–2024 with a typical study size of 131 participants.
Based on 7 studies · 1 meta-analysis · 3 RCTs · 437 total participants
Confidence
ModerateBy outcome
Butterbur has an evidence score of 6/10 — moderate evidence based on 7 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, so ONLY certified PA-free extracts should ever be used. 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. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
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Last reviewed June 2026 · evidence from 7 studies · how we score
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.
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 randomized trials show it works for allergic rhinitis comparably to antihistamines without sedation. 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.
50-75mg PA-free standardized extract twice daily for migraine prophylaxis (≈100-150mg/day); allergic rhinitis similar
Take with food
| Form | Type |
|---|---|
| 💊Certified PA-free standardized extract | Recommended |
| 💊Petadolex | Alternative |
| 💊Ze339 | Alternative |
Only PA-free certified products — raw butterbur is hepatotoxic.
Minimum: 8 weeks
Optimal: 16 weeks
Cycling: Trials often run 3-4 months; periodic liver-function monitoring is prudent. Reassess need rather than using indefinitely.
Note: Twice daily with food.
Dose-response data unavailable. The current published research for Butterbur does not provide sufficient dose-specific outcome data to generate reliable dose-response curves.
Refer to the Dosage & Timing section above for recommended dose ranges based on available evidence.
Reduces migraine attack frequency at 75mg twice daily.
Relieves allergic-rhinitis symptoms comparably to antihistamines.
Non-PA-free products carry hepatotoxicity risk.
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 use only PA-free extracts.
Tip: Take with food; most common reported effect
Tip: Use only certified PA-free extracts; stop and seek care if jaundice/dark urine/abdominal pain
Tip: Avoid if allergic to ragweed/daisies
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. The most commonly reported side effects are burping/GI upset, liver injury (with PA-containing products), allergic reaction (Asteraceae). Use caution if any of these apply to you: Liver disease; Pregnancy and breastfeeding; Allergy to ragweed/daisy family (Asteraceae).
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