Petasites is a genus of flowering plants in the sunflower family, Asteraceae, that are commonly referred to as butterburs and coltsfoots. They are perennial plants with thick, creeping underground rhizomes and large rhubarb-like leaves during the growing season.


Petasites is a shrub with incredibly huge leaves, up to 3 feet in diameter, usually found in low-lying wet areas and marshes. The plant is sometimes called butterbur, perhaps because the large, soft leaves were used to wrap butter when trying to keep it cool. Other colorful names for the plant include butterfly dock, butter-dock, bog rhubarb, flapperdock, and umbrella leaves. By whatever name, the plant is quite toxic. Butterbur was used in the Middle Ages to try to treat the plague. More recently, there has been some evidence suggesting that it might help in the treatment or prevention of migraines, asthma, ulcers, and now hay fever.

I’ve seen several headlines promoting the use of butterbur tablets (also called petasites tablets) as a gentle, natural remedy for those who want to treat hay fever without antihistamines. There are two important questions: Do they work? And are they safe? I’m excited that people have been looking into butterbur. I’m always glad to see alternative remedies evaluated. These results are particularly important.


One study, conducted by the Petasites Study Group in Switzerland, took 125 adults with hay fever and randomly assigned then to take petasites (butterbur) 8 mg four times a day or cetrizine (Zyrtec) 10 mg once a day. The pills were disguised and dummy pills were included so that participants (and doctors) did not know at the time which treatment they were receiving. The results were published in the January 19th issue of the British Medical Journal. I was very hopeful as I began to read the study.

After 2 weeks, investigators found no difference in symptoms between the two groups – both treatments were reported to have improved hay fever allergies equally. However, I am quite skeptical of these industry-funded results. The purpose of ‘blinding’ a study is to eliminate bias. But they designed this study to show that these two treatments were the same – so interviewers would be tempted to score patients similarly, and the blinding does nothing to eliminate bias with this study design. Also – when scoring results, they did not look at patients’ reports of any allergy symptoms improved (sneezing, watery eyes, runny nose – anything!), just overall quality of life. Not a very sensitive way to find a difference. At best, this study had only 80% statistical power (a 20% chance that butterbur did not help at all), but the built-in bias and the insensitive tests used take away even that measure of confidence. I’m sad to say that this study did nothing to convince me that butterbur actually helps allergies (though it certainly may) – much less that it is as effective as cetrizine. But it is the side effect story that is of the gravest concern to me.

The total number of side effects observed in those two weeks was similar (16.4% of the petasites group and 17.2% of the cetrizine group). Those taking cetrizine most commonly reported drowsiness (even though it is supposed to be a non-sedating antihistamine). This side effect was considered significant by the investigators. Those taking petasites reported a broader range of side effects, including itching skin, itchy eyes, wheezing, diarrhea, GI upset, headache, and fatigue. The authors dismissed all of these because no single side effect occurred in more than two people. To me they suggest a pattern of potential allergic reactions, which makes sense in that butterbur is a relative of ragweed. One patient had elevated liver enzymes in the blood (enzymes that indicate the destruction of healthy liver cells). This was also dismissed. I wonder how many patients would have had elevated liver enzymes if the test went on for 4 weeks?


Natural petasites (butterbur) contains highly toxic alkaloids that are known to seriously damage the liver and to cause cancer. They have also been associated with potentially fatal blood clots and with chronic scarring of the lung. Even small traces of these alkaloids are considered quite dangerous. Some commercial preparations are available where these alkaloids have been removed. They may work as well as the natural product, but we do not know. Nevertheless, butterbur in any form should not be used by women who are pregnant or who are nursing – all the more so in countries like the United States where herbs and supplements are not well-regulated.

Of greater concern to me: does the very ingredient supposedly responsible for improving many of the symptoms cause long-term problems? The active ingredient S-petasin would be expected to have a possible impact on the reproductive system. The one study looking at this carefully, published in the September 30, 2000 Clinical Journal of Physiology, found that s-petasin caused a dramatic impairment of testicular function when given to rats at tiny trace doses. Baseline testosterone production fell.

I would certainly not recommend giving butterbur to children before puberty, unless more evidence becomes available. The evidence in the BMJ article was crafted to sound convincing, but did not prove that butterbur is either safe or effective for treating allergies (methodological flaws have long plagued butterbur research). By conducting the study in a backwards way, the investigators took the power out of their randomized, placebo-controlled, double blind study. Designing a study to find the truth yields valuable information. Designing a study to promote a product can leave you with nothing but questions. Still, the butterbur story teaches us how possible it is to manipulate statistical evidence and to convince the popular press. It also illustrates that “herbal” and “natural” do not necessarily mean “safe” or “gentle”.

Should You Take Butterbur for Allergy Relief? Allergic rhinitis is a common allergy, affecting more than 35 million people in the United States. In allergic rhinitis, exposure to such allergens as pollen, mold spores, dust mites, or pet dander can lead to a runny nose, sneezing, and itching of the eyes and nose. This type of allergic reaction occurs because your body’s immune system releases histamine and leukotrienes, which can cause inflammation of the lining of the nose.

The active ingredient in butterbur, a member of the daisy family which is also known as Petasites hybridus, is called petasin. Petasin is thought to combat the leukotrienes and histamines that lead to an allergic reaction in people with allergic rhinitis. But the evidence supporting the benefits of butterbur is still preliminary, and more research is needed to determine butterbur’s effectiveness, as well as the optimal dosage and whether it is safe.

Safety is a serious concern, because butterbur “may contain a certain type of chemical, or an alkaloid, that has liver and kidney toxicity, may be cancer-causing, and may cause blood clots,” says Dr. Bowser, who works at Narberth Allergy & Asthma in Narberth, PA. Bowser cautions that you cannot be completely sure what you’re getting when purchasing a supplement. Unlike medications, the Food and Drug Administration does not ensure that a dietary supplement is safe before it is marketed. “Since it is not FDA-controlled, you can have varying amounts of the active ingredient in a supplement,” she says.

Bowser also notes that individuals who have a ragweed allergy should avoid butterbur, which is related to ragweed. “It may cause an allergic reaction in a ragweed-sensitive person,” she says.

Before taking butterbur or any other herbal remedy, it’s important to talk with your doctor, Bowser says. Some herbal supplements can react with other supplements or medications, so it is important to tell your doctor and pharmacist everything you are taking.

And remember, because the manufacturers of a supplement advertise their product as being natural does not necessarily mean that it is safe. “Natural does not mean safe or without side effects,” Bowser says.

For now, waiting for more research on butterbur’s possible effectiveness may be the safest policy.


How does butterbur work?

When your body comes into contact with an allergen, it releases the inflammatory chemical leukotriene. Leukotriene is what’s responsible for triggering an allergic reaction in your body.

Leukotriene (LT) inhibitors block leukotriene and prevent or relieve an allergic reaction. Butterbur seems to act as an LT receptor inhibitor, much like the drug Singulair (montelukast) used to treat nasal allergies.

However, researchers haven’t yet found that it is useful in treating asthma or skin allergies.

What are the risks of using butterbur?

Unprocessed butterbur contains chemicals called pyrrolizidine alkaloids (PAs). PAs can cause serious liver damage and other illnesses.

However, the National Institutes of Health (NIH) reports that PA-free butterbur products are safe, effective, and don’t cause side effects in most people. They should be taken by mouth in the recommended doses for 12 to 16 weeks. However, it is not known if using butterbur for a long period of time could cause problems.

Most people tolerate butterbur well, but it may cause side effects in some people. Side effects most often affect those who are allergic to plants. Because butterbur is part of the daisy family, you should avoid using it if you are allergic to plants in that family. Side effects may include:

  • allergic reactions
  • belching
  • headaches
  • itchy eyes
  • digestive problems
  • fatigue
  • sleepiness

You should always talk to your doctor before starting an alternative allergy treatment. Because butterbur could cause allergic reactions, it should only be given to children under a doctor’s supervision. It’s also important that if you use butterbur products you make sure that they are processed and labeled as PA-free.



Trials in migraine, allergic rhinitis, and asthma have used butterbur extracts in dosages ranging from 50 to 75 mg twice daily. Tesalin 16 to 32 mg in divided doses has been used in allergic rhinitis. Trials have included subjects 6 years of age and older.



Consider the use of butterbur-containing preparations in congestive heart failure a relative contraindication because of negative chronotropic effects demonstrated in animal experiments.


Contraindicated. Preparations may contain liver toxins with carcinogenic and mutagenic potential.


None well documented.

Adverse Reactions

GI symptoms comprise the majority of reported adverse reactions. Inhibition of testosterone production has been reported.


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