Lonicerae Flos containing formulation, Geumeumyoungji-tang (GYT), is an herbal prescription prepared using 5 different herbal drugs, namely, Lonicerae Flos, Ganoderma, Lactucae Herba, Xanthii Fructus, and Smilacis Rhizoma. This study was focused on the investigation of the pharmacological effects of GYT on allergic reactions. As the first step of the study, GYT was administered BALB/c mice which were sensitized by 2,4-dinitrofluorobenzene (DNFB). As the result GYT ameliorated dermatitis provoked by DNFB. The serum IgE level of the DNFB sensitized-mouse was significantly decreased when GYT was administered. In order to confirm the moderating effect of this prescription on allergic reaction, GYT was pretreated to human mast cells (HMC-1) before they were stimulated by phorbol-12-myristate 13-acetate plus calcium ionophore A23187 (PMACI). GYT suppressed secretion of inflammatory cytokines, interleukin (IL)-6 and IL-8, from HMC-1. Additionally, pretreatment of GYT showed regulating effect on COX-2 expression. Collectively, these findings provide insights into the pharmacological actions of GYT as a potential agent for treatment of allergic dermatitis.