Probiotic strains have been reported to have the ability to control allergic and inflammatory diseases. In this study, we studied the inhibitory effect of Bacillus subtilis (natto) (BS) on atopic dermatitis. The effects of continuous oral administration of BS for 4 weeks on the development of atopic dermatitis induced by Dermatophagoides farinae body antigen (DF) in NC/Nga (NC) mice were evaluated using 4 groups of mice: group (Gp) DF, DF(+) with no administration of bacteria (n=3); Gp DF/BS, DF(+) and BS(+) (n=5); and Gp PBS, DF(-) with no administration of bacteria (n=3). The mice were gavaged with 1.2 × 10(17) CFU/head of BS 6 times a week for 4 weeks, and DF was applied twice a week for 4 weeks. Histopathological examination revealed significant differences in auricular thickness between Gp DF (664.4 µm, SD=78.0) and Gp DF/BS (278.7 µm, SD = 88.8; p<0.01). The dorsal skin of Gp DF/BS (316.7 µm, SD=187.4) was significantly thinner than that of Gp DF (503 µm, SD=116.3). These results suggest that continuous oral administration of fermented food-derived bacteria (BS) can be effective in alleviating the development of skin lesions induced by DF in NC mice.