Effects of the aqueous extract of Cryptotympana atrata Fabricius (CAF) on the allergic reactions were investigated. In the present study, we examined the effect of CAF on compound 48/80-induced anaphylaxis in vivo and histamine release from rat peritoneal mast cells in vitro. CAF dose-dependently inhibited systemic anaphylaxis induced by compound 48/80 in mice. CAF significantly inhibited serum histamine levels induced by compound 48/80. CAF also inhibited histamine release from the rat peritoneal mast cells activated by compound 48/80. These results suggest that CAF may be useful for the prevention and treatment of allergy related disease.