Anti-allergic effect of an aqueous extract of wu-hu-tang.

Wu-Hu-Tang (WHT), a Chinese formulation which consists of seven crude drugs, has been used for the treatment of asthma for hundreds of years. In this paper, an investigation on the anti-allergic activity of an aqueous extract of WHT was undertaken to find the pharmacological basis for the ethnomedical use of the formulation. WHT produced a significant inhibition on the homologous passive cutaneous anaphylaxis (PCA) in rats and the heterologous PCA in mice, decreased the degranulation of mast cells of calvarial periosteum in rats, inhibited the release of anaphylactic mediators from sensitized lung tissues of guinea pigs and the contraction of isolated guinea pigs ileum induced by histamine. These results indicated that the therapeutic activity of WHT for asthma may be related to its inhibitory effects on immediate hypersensitivity.