We investigated 29 Lactobacillus strains isolated from Japanese traditional fermented food products made from rice grain or bran in order to select strains that potently suppress IgE production. First, in vitro screening was carried out to select candidates with strong induction activity for IL-12 and INF-γ production and suppression activity for IL-4 production in mouse splenocytes. Based on the screening data, 3 strains were selected and orally administrated to ovalbumin (OVA)-immunized mice. Among these 3 strains, Lactobacillus paracasei K71 (L. paracasei K71) isolated from sakekasu (sake lees) was shown to be the most potent for decreasing total and OVA-specific IgE levels in serum. L. paracasei K71 may downregulate IgE production via the induction of Th1 responses and suppression of Th2 responses in vivo.