What is Butterbur?

Butterbur (Petasites hybridus) is a flowering marsh plant that grows across Europe and northern Asia. Its large, umbrella-like leaves historically sheltered butter from summer heat, earning it its common name. The root extract has been used in European folk medicine since at least the Middle Ages to treat fever, plague symptoms, and pain.

How does Butterbur work?

The active compounds — petasin and isopetasin — appear to block certain inflammatory signaling molecules (leukotrienes and prostaglandins) that drive migraine pain and allergic reactions. They also seem to relax smooth muscle in blood vessels and airways, which may help reduce the intensity of migraine attacks and ease breathing in allergy sufferers.

What forms does Butterbur come in?

Only use standardized, PA-free root extract products — the most studied form is a CO2-extracted product standardized to 7.5–15% petasin. Raw butterbur root, teas made from unprocessed plant material, and any product without a PA-free guarantee should be strictly avoided due to liver toxicity risk.

Where it comes from:

Medieval European herbalists used butterbur to treat plague, fever, and urinary spasms. By the 17th century, it was a recognized remedy for coughs and asthma in Germany and England. Modern clinical interest accelerated in the 1990s when Swiss researchers began isolating and studying its anti-inflammatory petasin compounds.

What does Butterbur help with?

Butterbur is a marsh plant from Europe and parts of Asia. Healers there used the root for headaches, allergies and cramps for hundreds of years. Most modern study has looked at extracts made from the root.

• Getting fewer migraine attacks
  Strong evidence — repeated randomised trials in people, as held on file. Butterbur root extract is one of the most studied herbal options for migraine. In trials, daily use over several weeks cut how often attacks came and how bad they felt. It was used as a daily preventive, not as a painkiller during an attack.
  Evidence grade A · Traditional tier T2
• Hay fever and other seasonal allergies
  Strong evidence — clinical trials that compared it head to head with antihistamine drugs. Trials put butterbur extract up against the antihistamines cetirizine and fexofenadine. Symptom relief was similar, and people felt less drowsy on butterbur. Sneezing, runny nose and eye irritation all eased.
  Evidence grade A · Traditional tier T2
• A stuffy nose and sneezing from allergies
  Good evidence — symptom scores measured inside the allergy trials. In those allergy trials, stuffiness, sneezing and post-nasal drip went down. The effect showed up most when symptoms were allergy-driven. In lab studies, butterbur blocked the release of leukotrienes, molecules that drive swelling in the nose.
  Evidence grade B · Traditional tier T2
• Nose allergies that last all year
  Early evidence — early human work, weaker than the seasonal hay fever trials. Some human work points to help with nasal allergy symptoms outside pollen season. In lab studies, butterbur damped the chemical chain behind swelling and congestion. People in these studies did not report the sleepiness some antihistamines bring.
  Evidence grade C · Traditional tier T2
• Itchy, watery eyes from allergies
  Early evidence — eye symptoms tracked as a side measure in rhinitis trials. Several allergy trials also wrote down how people's eyes felt. Itchy and watery eyes improved along with the nose symptoms.
  Evidence grade C · Traditional tier T2
• Asthma set off by allergies or exercise
  Early evidence — early, small human trials only. Early human trials suggested butterbur relaxed the airways somewhat. Breathing felt easier for some people whose asthma was triggered by allergies. It was studied for day-to-day comfort, not as a rescue treatment.
  Evidence grade C · Traditional tier T2
• Frequent tension or vascular headaches
  Long traditional use · not yet tested in trials — lab work on smooth muscle plus the migraine data; no human trial on this use is on file. In lab studies, butterbur relaxed smooth muscle and calmed swelling. Some suggest this could help people with frequent non-migraine headaches. No human trial on file has tested that idea.
  Evidence grade insufficient · Traditional tier T2
• Belly and bladder cramps
  Long traditional use · not yet tested in trials — European tradition and lab work on smooth muscle only. Old European practice used butterbur for painful gut and urinary cramps. Lab work on smooth muscle gives a plausible reason why. Modern human evidence for these uses is thin next to the migraine and allergy data.
  Evidence grade insufficient · Traditional tier T2

What Butterbur has not been shown to do

• It has not been shown to stop a migraine once the pain has begun; trials used it daily, ahead of time.
• It has not been shown to give fast headache relief; in trials any benefit built up over weeks.
• It has not been shown to work as a rescue treatment in an asthma attack, so it does not stand in for an inhaler.
• It has not been shown in modern trials to ease belly or bladder cramps; that use rests on tradition.

How to read this:

A grade of A means steady results across randomised human trials. B means at least one good human trial. C means small or early human work. D means the human evidence is weak or clashes. Insufficient means no human study at all, just lab, animal or traditional use. Our file does not list the size or the dose used in each butterbur trial, so we do not state them here. This page shares options and study findings, not advice, and it is not a promise of results. Talk with your own clinician before you start, since butterbur products differ a lot.

What can Butterbur help prevent?

• Migraine attack frequency (well-supported by clinical trials: daily use shown to reduce attack frequency by roughly 50% in some studies)
• Allergy-season symptom flare-ups (consistent daily use before and during allergy season may reduce peak symptom severity)

Which foods are rich in Butterbur?

Butterbur's active compounds (petasin and isopetasin) are not meaningfully present in any common food — only in the butterbur plant itself. However, an anti-inflammatory diet supports the same pathways butterbur targets. Prioritize oily fish (salmon, mackerel, sardines) for omega-3s that reduce prostaglandins; colorful vegetables rich in quercetin (onions, apples, kale) that naturally calm histamine and leukotriene release; and turmeric and ginger which inhibit similar inflammatory enzymes. Limiting processed vegetable oils (sunflower, corn oil) and sugar can also reduce the underlying inflammatory load that drives both migraines and allergic reactions. If you take butterbur for migraines, reducing caffeine, alcohol, and aged cheeses is also worthwhile as these are common dietary migraine triggers.

What are the side effects of Butterbur?

• Burping or belching (most commonly reported side effect in trials, usually mild and transient)
• Nausea or stomach upset (especially on an empty stomach)
• Headache or fatigue in early days of use
• Allergic skin reaction (more likely in people with ragweed or daisy family allergies)
• Liver injury risk with non-PA-free or raw preparations: this is serious and not a minor effect

Good to know:

PA-free, standardized butterbur extract is considered safe for most adults when used as directed and for appropriate durations. The critical safety rule: only use certified PA-free products. Raw or unpurified butterbur can cause serious liver damage and is not safe under any circumstances.

How much Butterbur should you take?

• Recommended daily: 50–75 mg of standardized PA-free extract (standardized to 7.5–15% petasin), taken twice daily (100–150 mg total per day). The most-studied dose in migraine trials is 75 mg twice daily.
• Best time of day: Morning and evening, splitting the daily dose into two equal portions
• With or without food: Always take with food — this meaningfully reduces the likelihood of nausea and burping
• Time to effect: Allergy symptoms: 1–2 weeks; Migraine prevention: 4–12 weeks of consistent daily use
• How long to take it: Clinical trials have studied butterbur for up to 16 weeks continuously. Long-term safety beyond this window is not well established — take breaks of 4–8 weeks every 3–4 months and reassess with a healthcare provider. Do not use continuously for more than 4–6 months without professional guidance.