In this study, the effects of water extracts of fermented rice bran (FRBE) on immediate-type allergic reactions in vitro (RBL-2H3 cell line) and in vivo [ovalbumin (OVA) sensitized mice model] were investigated. FRBE inhibited ${eta}$-hexosaminidase release from RBL-2H3 cells activated by anti-dinitrophenyl (DNP) IgE while FRBE pretreatment profoundly inhibited the systemic allergic reaction induced by compound 48/80. Moreover, FRBE had a significant inhibitory effect on the mRNA expression of anti-DNP IgE-induced tumor necrosis factor (TNF)-${alpha}$, interferon (IFN)-${gamma}$, interleukin (IL)-4, IL-6, and IL-10, all of which mediate inflammatory reactions triggered by allergic reaction. To determine the mRNA levels of cytokines in an OVA-sensitized mice model after FRBE treatment, spleen cells were harvested with several concentrations of FRBE. The FRBE-treated group showed decreased levels of TNF-${alpha}$, IFN-${gamma}$, IL-6, and IL-10. These results suggest that FRBE suppressed allergic and inflammatory reactions through inhibition of degranulation, histamine release, and pro-inflammatory cytokine production from mast cells.