Atopic dermatitis (AD) is characterized as a multi-factorial inflammatory skin disease that has been increasing worldwide. Previously, we demonstrated that FPG, which is Platycodon grandiflorum (PG) fermented by Lactobacillus plantarum (LP), increases the level of interferon (IFN)-gamma in mouse splenocytes in vitro. In this study, we investigated the effects of FPG in an animal model of AD, with a particular emphasis on its effects on T helper (Th)1 and Th2 immune responses. To assess the potential use of FPG for the inhibition of AD, we established a model of AD-like skin lesions in NC/Nga mice. Immunoglobulin isotypes (Igs) and Th1/Th2 cytokines in the sera and spleens of AD-like mice were examined. In addition, histological examination was also performed. AD symptoms in skin lesions improved following oral administration of FPG. IgE secretion was significantly down-regulated, and this was accompanied by decreased levels of interleukin (IL)-4 and IgG1 and increased serum levels of IL-12p40 and IgG2a in FPG-treated animals. In splenocytes, the production of the Th1 cytokines IL-12p40 and IFN-gamma was up-regulated, while the levels of the Th2 cytokines IL-4 and 5 were down-regulated by FPG treatment. These results suggest that FPG inhibits the development of AD-like skin lesions in NC/Nga mice by suppressing the Th2 cell response and increasing the Th1 cell responses. Our results indicate that FPG is safe and effective for the prevention of AD-like skin lesions.