What butterbur is and how it may work in the body
Butterbur is a plant native to Europe and Asia whose root and leaf extracts have been studied for effects on inflammation and allergic reactions. The plant contains compounds called petasins and isopetasins, which appear to reduce the activity of inflammatory molecules in the body — specifically, they may lower levels of leukotriene and histamine, two chemical messengers involved in allergic responses and inflammation.
The extracts used in research are usually standardized to contain a specific amount of petasin, often around 15% by weight. This matters because the whole plant or unstandardized powders may contain different amounts of active compounds, and some parts of butterbur contain pyrrolizidine alkaloids — compounds that can damage the liver if consumed in large quantities. Most commercial supplements sold in the United States have had these alkaloids removed, though you should check the label.
Butterbur has been used in traditional medicine for centuries, but the modern research interest began in the 1990s when European researchers started testing standardized extracts in controlled trials. The mechanism is plausible — the compounds do appear to affect inflammatory pathways in laboratory and animal studies — but the human evidence is limited to a small number of trials, mostly conducted in Europe.
Key Takeaways
- Butterbur root extract has shown effects on allergic rhinitis (seasonal and year-round nasal allergies) in several human trials, with some studies finding it comparable to cetirizine (Zyrtec) for symptom relief.
- The evidence for migraine prevention is weaker; one moderate-quality trial found benefit, but larger or more recent trials are lacking.
- Most research used standardized extracts with pyrrolizidine alkaloids removed, so whole-plant powders or unstandardized products may carry different risks and benefits.
- Common side effects in trials were mild and included gastrointestinal upset and headache, though serious liver injury is theoretically possible with high doses of alkaloid-containing products.
Butterbur and allergic rhinitis: what the trials show
The strongest evidence for butterbur involves seasonal and year-round nasal allergies. A 2002 trial published in Clinical & Experimental Allergy compared a standardized butterbur extract (Ze 339, containing 15% petasin) to cetirizine in 186 people with seasonal allergic rhinitis. Both groups showed similar reductions in sneezing, nasal congestion, and itching over a four-week period, with butterbur performing roughly as well as the antihistamine.
A smaller 2005 trial in the same journal tested butterbur against placebo in 40 people with year-round allergic rhinitis and found statistically significant improvements in nasal symptoms and quality-of-life measures. However, the trial was brief (two weeks) and the sample was small. A 2007 Cochrane review of butterbur for allergies concluded that the evidence suggested benefit but noted that most trials were short, used different doses and extracts, and were conducted by researchers with financial ties to the supplement manufacturer.
These trials used doses of 50 to 75 mg of standardized extract per day, taken in divided doses. The effect size was modest — butterbur reduced symptoms but did not eliminate them, and it took one to two weeks to see results. No trial has directly compared butterbur to newer antihistamines like fexofenadine or to intranasal corticosteroids, which are considered first-line treatment for moderate to severe allergic rhinitis.
Butterbur for migraine prevention: limited and mixed evidence
One moderate-sized trial has examined butterbur for migraine prevention. A 2004 study in Neurology randomized 245 people with episodic migraines to receive either butterbur extract (75 mg twice daily) or placebo for four months. The butterbur group experienced a 48% reduction in migraine frequency, compared to 36% in placebo — a difference that was statistically significant but modest in absolute terms.
This trial is often cited as evidence that butterbur works for migraines, but it has limitations. The placebo response was unusually large (36% reduction), which suggests either a strong placebo effect or that the population was prone to natural improvement. The trial was funded by the manufacturer of the butterbur product tested. No large, independent trial has replicated the finding, and no trial has compared butterbur to established migraine preventives like propranolol or topiramate.
A 2015 systematic review found only this one trial of adequate quality for migraine prevention and concluded that evidence was insufficient to recommend butterbur over standard treatments. The American Academy of Neurology does not list butterbur as a recommended preventive for migraines, though it does not rule out potential benefit from future research.
Other proposed uses with weaker evidence
Butterbur has been studied for asthma, urinary tract symptoms, and general inflammation, but the evidence is sparse or of low quality. A small trial suggested it might reduce asthma symptoms, but the sample was tiny and the study design was weak. No rigorous trials have tested butterbur for urinary symptoms or for general inflammatory conditions like rheumatoid arthritis.
Laboratory and animal studies show that butterbur compounds do suppress inflammatory markers, which is why researchers continue to propose new uses. However, effects in cells or in mice do not reliably predict effects in humans, and without human trials, claims about benefit for other conditions remain speculative.
Safety, side effects, and who should avoid butterbur
In the trials reviewed above, butterbur was generally well tolerated. The most common side effects were mild gastrointestinal upset (nausea, diarrhea, constipation) and headache, each occurring in roughly 5 to 10% of participants — rates similar to placebo. Allergic reactions were rare but documented.
The main safety concern involves pyrrolizidine alkaloids, compounds found naturally in butterbur that can cause liver damage and are potentially carcinogenic at high doses. Most commercial butterbur supplements sold in the United States have been processed to remove these alkaloids, but not all. Check the label for language like "PA-free" or "pyrrolizidine alkaloid-free." Whole butterbur plant material, teas made from the raw plant, or products from outside the United States may contain significant amounts.
Butterbur should be avoided by people with liver disease, by pregnant or breastfeeding women (insufficient safety data), and by anyone with a known allergy to plants in the Asteraceae family (ragweed, chrysanthemums, daisies). People taking anticoagulants or antiplatelet drugs should discuss butterbur with their doctor, as some evidence suggests it may have mild anticoagulant properties, though this is not well established.
How butterbur compares to other allergy and migraine options
For allergic rhinitis, butterbur has been tested against cetirizine and performed similarly in one trial, but it has not been compared to intranasal corticosteroids (fluticasone, mometasone), which are more effective for moderate to severe symptoms and are considered first-line by allergists. Butterbur may be an option for people who prefer to avoid antihistamines or steroids, or who have not responded to them, but the evidence does not support it as a first choice.
For migraine prevention, butterbur has far less evidence than established options like propranolol, topiramate, or amitriptyline. The single positive trial was small and had a large placebo response. If you are considering butterbur for migraines, discuss it with a neurologist or headache specialist who can weigh it against treatments with stronger evidence and help you monitor for benefit.
What questions remain unanswered
The research on butterbur leaves several gaps. Most trials were small, short, and conducted in Europe by researchers with financial ties to supplement makers. No large, independent trial has tested butterbur against placebo or against standard treatments in the United States. The optimal dose is unclear — trials used 50 to 75 mg daily, but whether lower or higher doses work better is unknown.
Long-term safety data are sparse. Most trials lasted four weeks to four months; no trial has followed people taking butterbur for a year or longer. The effect of butterbur on people taking other medications is not well studied. And for most proposed uses beyond allergies — asthma, migraines, general inflammation — human evidence straightforward does not exist.
Frequently Asked Questions
Is butterbur safe to take long-term?
Short-term use (up to four months) appears safe in trials, with mild side effects. Long-term safety is unknown because no trial has followed people for more than a few months. If you take butterbur regularly, choose a product labeled PA-free and discuss duration with your doctor, especially if you have liver disease or take other medications.
Can I take butterbur with antihistamines or other allergy medications?
No trials have tested butterbur combined with antihistamines or corticosteroids, so the interaction is unknown. Talk to your doctor or pharmacist before combining butterbur with any allergy or migraine medication to check for potential interactions.
How long does it take butterbur to work?
In trials for allergic rhinitis, people began to notice symptom improvement after one to two weeks of daily use. For migraines, the one trial took four months to measure benefit. If you try butterbur, allow at least two to four weeks before deciding whether it is helping.
Is butterbur better than antihistamines for allergies?
One trial found butterbur comparable to cetirizine, but it has not been tested against newer antihistamines or against intranasal steroids, which are more effective for moderate to severe allergies. Butterbur may be an option if you prefer herbal products or have not responded to standard treatments, but the evidence does not show it is superior.
What does "PA-free" mean on a butterbur label?
PA stands for pyrrolizidine alkaloid, a naturally occurring compound in butterbur that can damage the liver at high doses. PA-free means the product has been processed to remove these alkaloids. Always choose PA-free butterbur supplements to reduce the risk of liver injury.