We examined the effect of 59 strains of heat-killed Lactobacillus brevis on interleukin (IL)-12 and interferon (IFN)-gamma production from mouse Peyer's patch (PP) cells. L. brevis has a great variety of strains that induce the production of these cytokines. Some L. brevis strains, which were selected for their ability to induce a strong Th1 immune response, inhibited both total immunoglobulin E (IgE) and antigen specific IgE production, and improved the Th1/Th2 balance by enhancing IL-12 and IFN-gamma and inhibiting IL-4 production from ovalbumin (OVA)-sensitized mouse splenocytes. Based on the results of this screening, we selected L. brevis SBC8803 as a potent inhibitor of IgE production, and investigated the effect of oral administration of heat-killed SBC8803 on IgE production in OVA-sensitized mice. OVA-sensitized mice were fed SBC8803 0% (control), 0.05%, or 0.5% added diet for 4 weeks during the period of the experiment. Total and OVA-specific IgE in the serum of mice, which were fed the 0.5% added diet, was significantly lower than that of the control diet fed mice. The IFN-gamma/IL-4 value, which represents the Th1/Th2 balance, from the 0.5% added diet fed mice splenocytes was also significantly higher than that of the control diet fed mouse splenocytes. Histamine release from OVA-sensitized mice into sera that were induced by the intraperitoneal antigen challenge decreased following the oral administration of SBC8803. The inhibition of IgE production and histamine secretion by the oral administration of heat-killed SBC8803 was probably due to the improvement of the Th1/Th2 balance toward Th1 dominance.