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 isstill not fully understood. The aim of the present study is to elucidate whether and how SSEmodulates the allergic reactions in vivo, and inflammatory reaction in vitro. In this study, weshowed 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 ofinflammatory 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 throughsuppression of nuclear factor-κB activation and IκB-α phosphorylation/degradation in HMC-1.These results provided new insight into the pharmacological actions of SSE as a potentialmolecule for therapy of inflammatory allergic diseases.