The effects of orally administered lactic acid bacteria metabolites on the skin were studied using an atopic dermatitis-like murine model created by feeding mice with HR-AD. The lactic acid bacteria metabolites were obtained by inoculating 35 strains of 16 species of lactic acid bacteria into soy milk and culturing them. The atopic dermatitis-like murine model was created by feeding HR-1 mice HR-AD for 40 days. The skin condition of mice that were fed HR-AD worsened compared with normal mice, i.e., reduced water content in the stratum corneum, increased transepidermal water loss (TEWL), reduced ceramide AP content in the stratum corneum, and increased epidermis thickness. When mice that had been fed the HR-AD diet was administered a raw liquid of lactic acid bacteria metabolites orally, the measured values related to water content in the stratum corneum, TEWL, ceramide AP content in the stratum corneum, and epidermis thickness improved. To find out the active components for these effects, filtrate and residue from the raw liquid of lactic acid bacteria metabolites and lipid components extracted from the raw liquid were examined at the same time. Results showed that the water-soluble components or residue after filtration did not demonstrate effects but the raw liquid and the lipid fraction did. These findings suggest that lactic acid bacteria metabolites improve skin injury in an atopic dermatitis-like murine model.

Cosmetics have various characters, but there have been no studies which classified the properties of cosmetics based on their effects on skin-domesticated bacteria. In this study, we established an anaerobic culture and short-chain fatty acid measurement system using Staphylococcus epidermidis, a representative bacterium of indigenous skin bacteria. Furthermore, this system was used to extract and classify the characteristics of 9 cosmetics. Cosmetics containing ferments of rice and soy were clustered in the vicinity, although one cosmetic containing soy ferment was clustered distant from other similar cosmetics. Cosmetics from South Asia and those containing natural plant extracts were clustered in the vicinity. These results show that this method can be utilized as a cosmetics pattern map, and will provide a method to prevent growth of opportunistic bacteria.