Samsoeum (SSE) is used in traditional oriental medicine for various medicinal purposes. However, the exact mechanism that accounts for the anti-allergy and anti-inflammatory effects of the SSE is still not fully understood. The aim of the present study is to elucidate whether and how SSE modulates the allergic reactions in vivo, and inflammatory reaction in vitro. In this study, we showed that SSE significantly decreased compound 48/80-induced systemic anaphylaxis, ear-swelling response, histamine release from preparation of rat peritoneal mast cells and anti-dinitropheny IgE-induced passive cutaneous reaction. Also, SSE inhibited the expression of inflammatory cytokine and cyclooxygenase-2 in PMA plus A23187-stimulated human mast cells (HMC-1). In addition, we showed that anti-inflammatory mechanism of SSE is through suppression of nuclear factor-${kappa}B$ activation and $I{kappa}B-{alpha}$ phosphorylation/degradation in HMC-1. These results provided new insight into the pharmacological actions of SSE as a potential molecule for therapy of inflammatory allergic diseases.