Our previous study showed that the serum level of antigen-specific IgE antibodies in primary response was decreased by a traditional Chinese medicine, Bu-zhong-yi-qi-tang (Japanese name; Hochu-ekki-to, HOT). In this study, we examined inhibition of secondary IgE response and of eosinophil infiltration by HOT. BALB/c mice were intraperitoneally immunized with aluminum hydroxide adsorbed with DNP-KLH (DNP-KLH + alum) on day -14 and on day 0. In mice treated with HOT daily from day -14, the serum level of antigen-specific IgE antibodies after the secondary immunization was significantly decreased compared to that in mice not treated with HOT. Eosinophils increased in number after 6 and 24 hr, and CD4+ T cells in the peritoneal cavity increased in number 24 hr after the secondary immunization. HOT suppressed accumulation of eosinophils and CD4+ T cells in the peritoneal cavity. Furthermore, HOT suppressed the numbers of IL-4- and IL-5-producing cells 24 hr after the secondary immunization, but did not inhibit the number of IFN-gamma-producing cells. HOT also suppressed IL-5 mRNA expression. Furthermore, HOT also inhibited antigen-induced late-phase reaction (LPR) in the skin. These results suggested that HOT exhibited anti-allergic effects mainly by inhibiting Th2 cell responses.