Herbal medicines for asthma: a systematic review.

BACKGROUND Asthma is one of the most common chronic diseases in modern society and there is increasing evidence to suggest that its incidence and severity are increasing. There is a high prevalence of usage of complementary medicine for asthma. Herbal preparations have been cited as the third most popular complementary treatment modality by British asthma sufferers. This study was undertaken to determine if there is any evidence for the clinical efficacy of herbal preparations for the treatment of asthma symptoms. METHODS Four independent literature searches were performed on Medline, Pubmed, Cochrane Library, and Embase. Only randomised clinical trials were included. There were no restrictions on the language of publication. The data were extracted in a standardised, predefined manner and assessed critically. RESULTS Seventeen randomised clinical trials were found, six of which concerned the use of traditional Chinese herbal medicine and eight described traditional Indian medicine, of which five investigated Tylophora indica. Three other randomised trials tested a Japanese Kampo medicine, marihuana, and dried ivy leaf extract. Nine of the 17 trials reported a clinically relevant improvement in lung function and/or symptom scores. CONCLUSIONS No definitive evidence for any of the herbal preparations emerged. Considering the popularity of herbal medicine with asthma patients, there is urgent need for stringently designed clinically relevant randomised clinical trials for herbal preparations in the treatment of asthma.