What Is Butterbur?
Butterbur (any of the plants of the Petasites genus), also known as coltsfoot, is a flowering plant native to Asia, Europe, and North America. It has been used in traditional medicine for thousands of years to treat a wide range of ailments from high blood pressure (hypertension) and asthma to tumors. It was even used to treat plague and fever during the Middle Ages [1, 2].
There are several types of butterbur, though the most well studied are Petasites japonicus, also called giant butterbur and Petasites hybridus. Though related, the two are distinct species and may have different properties.
Petasites japonicus is eaten as a vegetable in Eastern Asia and also used in traditional medicine. Petasites hybridus is native to Europe, where it is not considered a culinary plant but is still consumed medicinally [3, 4, 5].
Petasites plants have to be processed in the laboratory to ensure they are safe to consume. One of these extracts is referred to as Butterbur Ze339 or Ze339 .
It is most commonly used for migraine and allergy relief and has been the subject of multiple clinical trials suggesting that it is an effective treatment for both conditions, in addition to containing beneficial chemicals that reduce inflammation, oxidation, and pain [7, 8, 9, 10].
This plant contains:
- Petasins, which reduce inflammation 
- S-isopetasin, petatwalide B, and bakkenolide B, which widen blood vessels and decrease inflammation [4, 11, 12]
- Flavonoids, which are antioxidants that decrease inflammation and fight bacterial infections and cancer 
- Pyrrolizidine alkaloids, which are toxic to the liver and may cause cancer. These can be removed in the laboratory [13, 5]
Mechanism of Action
The anti-inflammatory properties of butterbur are conferred mainly by molecules called petasins, which act to limit the body’s production of inflammatory molecules as:
- Leukotrienes [9, 14]
- Eosinophil cationic protein (ECP) and TNF-α [15, 16, 16]
- Interleukins IL-2, IL-4, IL-5, IL-6, IL-8 IL-13, and RANTES [17, 18, 19]
- Active STAT molecules [19, 20].
Butterbur may also relieve pain by decreasing the sensitivity of neurons. Isopetasin decreased the activity of the protein TRPA1, which is found on the surface of sensory neurons, decreasing neuron sensitivity and, thereby, pain [21, 22, 23].
Flavonoids from the leaves of Petasites japonicus activate :
- Nrf2, which controls the production levels of many genes affecting the body’s response to free radical damage. After activation by the flavonoids in butterbur, Nrf2 activated the HO-1 pathway that produces several chemicals including biliverdin, which is a powerful antioxidant [24, 10, 25].
- Heat-shock response transcriptional elements (HSE), that help coordinate the body’s response to stressors including sun damage. UV radiation can cause proteins to unfold and become nonfunctional. HSE activated by butterbur switches on the HSP70 pathway, which ensures proteins maintain their proper shapes [26, 10, 26].
Potential Health Benefits of Butterbur
1) Butterbur Relieves Migraines
The most common use of butterbur is for the relief and prevention of migraines and headaches.
In a study of 33 adults, butterbur extract decreased the average number of migraine attacks per month after 3 months of treatment. Overall, 45% of individuals treated with butterbur showed improvement compared to placebo .
Another study compared 245 adults over 4 months. There was a 48% decrease in migraine frequency in the group given butterbur extract, compared to 26% for the placebo group. In total, 68% of patients who received 75-mg reported improvement .
In a survey of 108 children aged 6 to 17, the rate of reported migraine attacks decreased by at least 50% in 77% of children. The study found that after 4 months of treatment with butterbur, 91% of patients felt “substantially” or “at least slightly improved” .
Butterbur root extract is currently recommended for short-term use by both the Canadian Headache Society and the American Headache Society for short-term prevention and treatment of migraine headaches [30, 31].
2) Helps with Hay Fever and Seasonal Allergies
Multiple studies have shown that butterbur can help relieve seasonal allergy symptoms.
In a survey of 580 people who took the extract for two weeks, 90% reported a reduction in seasonal allergy symptoms .
A study involving 186 patients with allergic rhinitis (hay fever) showed that butterbur extract (Ze339) decreased symptoms after just one week of treatment .
Another study involving 20 individuals reported that after two weeks of treatment with butterbur extract, patients had improved recovery time upon allergen exposure .
Two further studies, with a combined total of 346 patients, showed that butterbur (Ze339) was as effective as fexofenadine (Allegra) and cetirizine (Zyrtec) in reducing seasonal allergy symptoms. Both are antihistaminic drugs used to treat allergies [34, 35, 36].
Animal models showed that these effects are caused by a reduction in eosinophils (types of white blood cells) and leukotrienes in nasal tissue as well as a reduction in histamine, which contributes to the development of allergy symptoms [37, 38].
Though the majority of studies have used the Petasites hybridus variety of butterbur, one study suggests that Petasites japonicus is also effective in treating seasonal allergies .
Despite a large amount of promising research, there is some conflicting evidence. In a study of 35 patients, butterbur failed to improve hay fever symptoms, conflicting with other reports .
3) May Help with Asthma
Multiple studies have confirmed that butterbur can reduce asthma symptoms.
In a study involving 64 adults and 16 adolescents, who were given butterbur extract (Petasites hybridus) in addition to their normal asthma medication, 83% of patients showed an improvement in their symptoms .
In another study of 16 asthmatic patients, a combination of butterbur and inhaled corticosteroids showed reduced inflammation symptoms compared to treatment with corticosteroids alone .
These studies are supported by research on mice, which has shown that when given butterbur and then subjected to allergens, mice showed decreased inflammation in the lungs, reduced recruitment of immune cells to the inflamed areas, and reduced mucus secretion [17, 18].
Butterbur contains multiple compounds that contribute to the relief of asthma symptoms. S-iso-petasin may be acting as a bronchodilator, while petatewalide B and bakkenolide B reduce eosinophils, macrophages, and lymphocytes (all types of white blood cells) in the bronchial fluid [4, 11, 12].
4) May Be Neuroprotective
Butterbur extracts (Petasites japonicus) prevented the death of neurons in the brains of mice due to kainic acid, which mimics the effects of free radical damage to the brain. In addition to reducing neuron cell death, the mice also had fewer seizures [42, 43].
5) May Prevent Ulcers
Butterbur extract (Petasites hybridus) reduced the size of stomach ulcers in mice and protected against stomach damage caused by alcohol .
6) May Decrease Cholesterol Levels
7) May Combat Obesity
8) May Decrease Blood Pressure
S-petasin and iso-S-petasin, active compounds in butterbur, decrease blood pressure in rats. These compounds, decrease the activation of the smooth muscles surrounding the blood vessels, causing them to widen and, thereby, reduce blood pressure [49, 50, 51].
9) Is an Antioxidant
Although butterbur naturally contains molecules that cause liver damage, processed butterbur without these molecules actually increases the activity of antioxidant enzymes in the liver in mice.
Specifically, the enzymes which showed increased activity were glutathione reductase (GSR), glutathione peroxidase (GPx), glutathione S-transferase (GSTs), and quinone reductase (QR). These enzymes protect the liver from free radical damage [52, 48].
10) May Help Somatic Symptom Disorder
Somatic symptom (somatoform) disorders are a group of psychological disorders in which a patient experiences physical symptoms that can’t be explained by any underlying medical condition.
A study of 182 people with somatoform disorders reported that a combination of the herbs butterbur root, valerian root, passionflower herb, and lemon balm leaf significantly improved measures of anxiety and depression after two weeks of treatment. The same combination without butterbur was significantly less effective .
11) May Help in Male Fertility
In a mouse cell-based study, an extract of butterbur (Petasites japonicus) stimulated the growth of cells that produce sperm in test tubes .
However, it’s too early to tell if butterbur extract will have the same effect in humans.
12) May Prevent Blood Clots
Petasites japonicus contains a type of enzyme called a fibrolytic serine protease, which helps the proteins that form blood clots (fibrigins and fibrinogens) dissolve in the blood, preventing the blood clot from growing large. This enzyme has been shown to prevent blood clots (thrombosis) in mice and to promote the breakdown of human fibrins and fibrinogens [55, 56].
13) May Combat Cancer
An extract from the leaves of butterbur (Petasites japonicus) was shown to be toxic to stomach, colon, and uterus cancer cells .
This same extract also reduced the size of liver tumors in mice .
More research is needed to confirm if these effects are also seen when butterbur is taken as a supplement in humans.
Side Effects & Precautions
The most commonly reported side effects of butterbur supplements were gut-related, including belching, diarrhea, and nausea .
- Allergic conjunctivitis
- Allergic rhinitis
- Difficulty exhaling or difficulty breathing
- Dermal/allergic symptoms
- Itchy eyes
- Hair loss
- Reversible cholestatic hepatitis
- Severe nausea
- Severe depression
- Skin discoloration
- Stomach pain or flatulence
- Stool discoloration
Unprocessed Butterbur Is Toxic to the Liver
For this reason, it is important to choose butterbur supplements that have been produced by a reputable manufacturer. The products are typically labeled “PA-free.”
Little is known about the effects of butterbur on pregnancy. Due to the risk of accidental contamination with pyrrolizidine alkaloids, pregnant or breastfeeding women should avoid butterbur.
Potential for Allergies
People with allergies to Compositae plants (such as) may also be allergic to butterbur as butterbur belongs to the plant family (Asteraceae), which also contains ragweed, daisies, and chrysanthemums.
When taking butterbur products there is a risk of liver damage, so people with a compromised liver function should avoid them.
Several of the benefits have been studied in animals, but it is unknown whether butterbur would have the same effect on humans.
Also, the safety of the long-term use of butterbur has not been established.
There are a number of butterbur supplements on the market.
Recommended dosages for other uses have not been established.
- “The only nonprescription product, that has even touched my swollen sinuses.”
- “I have suffered from migraines and daily headaches for many years…I began to look for preventative measures that did not involve a prescription medication with many side effects and this is the answer!! Within the first week, I was noticing days with no headaches and fewer and less severe migraines. I highly recommend this to anyone suffering from chronic migraines.”
- “Taking as a migraine preventative. Did not notice any change. For me, it is not worth the risk of liver damage.”