DOES IT WORK? BUTTERBUR, ALSO called bog rhubarb, is found in Ireland and throughout Europe, North America and Asia. The plant grows in wet lowlands, especially along river banks. As its name suggests, its leaves look like those of rhubarb. Around this time of the year, before the leaves appear, distinctive lilac flowers emerge from the ground and extend several inches off the ground on the ends of sturdy stalks. Other species are called butterbur, but the one of medicinal interest is Petasites hybridus.

The plant has a long history of being used for many ailments, particularly gastrointestinal problems, asthma and coughs. Its popularity has been increasing recently, especially as a treatment for allergic rhinitis. This condition includes hay fever and similar allergic reactions to various pollens or dust. It affects people at various times of the year depending on which plants or trees are pollinating. The nasal and throat symptoms can affect some people throughout the year.

A number of commercial butterbur products are available. Each is made using a particular method of extracting the plant material. Each product is then standardised to contain a specific amount of active ingredient.

EVIDENCE FROM STUDIES

Extensive laboratory research has led to the isolation of several active ingredients. Several have been found to have anti-histamine effects. However, a number of pyrrolizidine alkaloids have also been isolated, especially from the rhizome (underground parts). These are toxic and will be discussed below.

In the past several years, a number of high-quality clinical trials have been published examining butterbur for allergic rhinitis. Most of these have involved either a German or Swiss product in trials sponsored by the manufacturer. About half of these studies compared butterbur to a placebo and found butterbur to be significantly better. The other studies compared butterbur with pharmaceutical anti-histamines and found the two treatments to be similarly effective. However, none of these studies lasted longer than two weeks, which is an important limitation given that these symptoms typically last much longer.

PROBLEMATIC ASPECTS

Most people do not have adverse reactions to butterbur. A Swiss manufacturing company surveyed those using their butterbur product and found that about 4 per cent of people had adverse effects. Most of these were stomach and intestinal problems.

However, as mentioned above, the underground rhizomes of butterbur contain pyrrolizidine alkaloids. These occur in a number of plants and are known liver toxins. The extraction process used by manufacturers should ensure that no pyrrolizidine alkaloids end up in commercial products. However, the Swiss company that developed one product, called ZE 339 or Tesalin, stated that it could not guarantee that liver problems might not occur. In 2004, butterbur products were removed from the market in Switzerland after reports of severe liver damage. Similar actions have not occurred elsewhere.

RECOMMENDATIONS

Allergic rhinitis can be highly irritating and disruptive. A number of pharmaceutical products are available, but they can have side effects. The evidence from a growing number of studies supports the use of butterbur products for the short-term relief of these symptoms. Long-term studies do not appear to be available.

Given the presence of pyrrolizidine alkaloids in butterbur, the plant material itself should not be consumed. Complex extraction processes allow manufacturers to make products which contain none of these compounds. However, only products that specifically state that they are free of pyrrolizidine alkaloids should be used. Once pyrrolizidine- free products are used, butterbur is normally safe and may provide welcome relief from hay fever symptoms.

Dónal O’Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University