Allergic contact dermatitis (ACD) is a type IV delayed hypersensitivity reaction that results from exposures and subsequent sensitization to an environmental chemical. Crataegus Pinnatifida (CP) is commonly used to improve spleen function, remove retention of food, and promote blood circulation. This study is designed to investigate the effects of CP on ACD induced by 2,4-dinitrochlorobenzene (DNCB) in mice. In this experiment, the effects of CP on changes in body weights, ear and dorsum skin thicknesses, ear weights, clinical aspects on the dorsum skin, histopathological changes, spleen weights, cytokines were investigated. In addition, the effects on the proliferation rates of splenocytes were also investigated in vivo and vitro study. In results, CP spread (CPS) group and CP spread and administered (CPS+Adm) group showed decrease in spleen weights. In CPS+Adm group, dorsum skin thicknesses were decreased significantly compared to control group. CP treatment diminished erythema, desquamation and keratosis which were induced by repeated painting of DNCB. In histopathological observation, spongiosis and edema were diminished in CPS and CPS+Adm group. CP led to decrease in the proliferation rates of splenocytes in vivo and vitro. In conclusion, these data suggest that CP can decrease symptoms of ACD, so CP is useful to treat patient with ACD.