An herbal extract has been shown in a clinical study to be as effective at treating hay fever as the antihistamine fexo-fenadine (Allegra or Telfast). The finding could boost the fledgling phytopharmaceutical industry, which scrutinizes natural remedies for efficacy and safety and hopes to develop them at lower cost than traditional pharmaceuticals. In the study, led by Andreas Schapowal at the Allergy Clinic in Landquart, Switzerland, patients took a placebo, Telfast, or Tesalin, a prescription drug prepared from an extract of the butterbur plant (Petasites hybridus) by the Swiss company Zeller AG (Phytotherapy Res. 2005, 19, 530). Butterbur roots have been used in herbal remedies for centuries. Zeller has patented a special cultivar and uses CO2 to extract active ingredients from the leaves. The most prevalent compound, petasine (shown), and its isomers are thought to inhibit synthesis of leukotrienes, which along with histamine and other compounds are synthesized as part of the immune response to an allergen.