Butterbur is an herbal supplement used primarily to prevent migraines and relieve seasonal allergy symptoms. These two uses have the strongest clinical evidence behind them, though the plant has a long folk history of treating pain, fever, coughs, and stomach complaints. Before trying it, you should know that butterbur carries real safety concerns, and its regulatory status has shifted in recent years.
Migraine Prevention
The best-studied use of butterbur is reducing how often migraines occur. A randomized trial published in Neurology tested butterbur extract at two doses against a placebo in 245 migraine patients over four months. The higher dose (75 mg taken twice daily) reduced migraine frequency by 48%, compared to 26% in the placebo group. Among those taking the higher dose, 68% experienced at least a 50% drop in attacks. The lower dose (50 mg twice daily) reduced attacks by 36%, but this wasn’t statistically significant compared to placebo.
In other words, the dose matters. The clinical benefit showed up clearly at 75 mg twice daily, while 50 mg twice daily performed only marginally better than a sugar pill. The extract used in this research was standardized to contain 15% of butterbur’s active compounds and was certified free of toxic alkaloids (more on that below).
Seasonal Allergy Relief
Butterbur has also been tested head-to-head against cetirizine (the active ingredient in Zyrtec) for hay fever. A randomized trial published in The BMJ gave 125 patients either butterbur tablets four times daily or cetirizine once daily for two weeks. Both groups improved by the same amount on quality-of-life scores and clinical assessments rated by patients and doctors alike.
The side effect profiles were also similar: about 16% of butterbur users and 17% of cetirizine users reported adverse events. The key difference was the type of side effects. Two-thirds of the adverse events in the cetirizine group involved drowsiness or fatigue, despite cetirizine being marketed as a non-sedating antihistamine. Butterbur didn’t cause that sedation, which makes it a potentially useful option for people who need allergy relief without feeling sluggish.
How Butterbur Works in the Body
Butterbur’s active compounds reduce inflammation through two main pathways. First, they block the production of leukotrienes, which are chemical messengers your immune cells release during allergic reactions and inflammatory responses. They do this by lowering calcium levels inside immune cells like eosinophils and neutrophils, which dampens those cells’ ability to ramp up inflammation. Second, they appear to interfere with a signaling pathway (called STAT) that drives broader inflammatory responses.
This dual action helps explain why butterbur shows up in both migraine and allergy research. Migraines involve neurological inflammation, and allergies involve immune-driven inflammation. Butterbur’s compounds target the underlying inflammatory machinery common to both conditions.
Other Traditional Uses
Historically, butterbur has been used for pain, anxiety, coughs, fever, and urinary tract complaints. A few small studies have also suggested possible benefits for asthma. However, the evidence for these uses is thin. The NCCIH, part of the National Institutes of Health, states there is not enough evidence to show butterbur is effective or safe for asthma or allergic skin reactions. Migraine prevention and seasonal allergies remain the only uses with meaningful clinical trial data.
Safety Concerns and Liver Toxicity
Butterbur contains naturally occurring compounds called pyrrolizidine alkaloids, which are toxic to the liver. In preclinical studies, these alkaloids have also shown carcinogenic and mutagenic properties. Manufacturers can remove most of these compounds during processing, and products labeled “PA-free” are supposed to contain only trace amounts.
Here’s the problem: even extracts with pyrrolizidine alkaloids removed have been linked to liver damage. Cases of liver toxicity have been reported with supposedly PA-free products, which suggests that either the removal process isn’t always complete or other components of butterbur may contribute to liver harm. This is not a theoretical risk. It’s the reason the American Academy of Neurology stopped recommending butterbur for migraine prevention in 2015, reversing an earlier endorsement.
Common, less serious side effects include belching, headache, itchy eyes, digestive discomfort, fatigue, and drowsiness.
Choosing a Butterbur Product
If you decide to try butterbur, the extract should be labeled PA-free and standardized to contain at least 15% of its active compounds (petasin and isopetasin). For migraine prevention, the effective dose in clinical trials was 75 mg taken twice daily. For seasonal allergies, the dosing schedule in the cetirizine comparison trial was one tablet four times daily.
Because butterbur supplements are not regulated the way prescription drugs are, quality varies between brands. The specific extract used in most published research was a German product called Petadolex. Not all butterbur supplements on the market have undergone the same level of alkaloid removal or third-party testing, which makes the liver toxicity concern especially relevant when choosing a product. Periodic liver function monitoring is something to discuss with your healthcare provider if you plan to use butterbur regularly.