In this report, we investigated the effect of aqueous extract of vinegar treated small black soybean (Glycine max Merr.) (Leguminosae) (VSBS) on mast cell-mediated allergic reaction and pro-inflammatory cytokine secretion. VSBS inhibited compound 48/80-induced systemic reactions. VSBS attenuated immunoglobulin (Ig) E-mediated passive cutaneous anaphylaxis. In addition, VSBS decreased the phorbol 12-myristate 13-acetate plus calcium ionophore A23187-stimulated secretion of tumor necrosis factor (TNF)-${alpha}$, interleukin (IL)-6 and interleukin (IL)-8 in human mast cells. Our findings provide evidence that VSBS inhibits mast cell-derived allergic reactions.