Background Although the physiological conditions of vulvar skin in Caucasian populations have been characterized, little is known about these conditions in Japanese women.
Methods Skin of the labia, groin, mons pubis, and inner thigh was examined in 40 healthy Japanese women outwith their menstrual period. Skin moisture, skin pH, ceramide content and inflammatory cytokine proteins of the stratum corneum, and bacterial flora were assessed.
Results Skin moisture was found to be significantly lower in the labia than at the other three sites examined. No differences were found in skin pH. A significant difference in ceramide content was observed between the groin and inner thigh. The ratio of interleukin-1α (IL-1α) and interleukin-1α receptor antagonist (IL-1Ra) was significantly higher in the labia than in the other sites. Numbers of total bacteria, Staphylococcus epidermis, and Lactobacillus spp. were greater in the labia and mons pubis sites compared with the inner thigh. Prevotella spp. were found only in the labia.
Conclusions In Japanese women, the skin at the labia is drier and more inflammatory than the skin at the groin, mons pubis, and inner thigh; this cannot be explained by the ceramide content and/or pH of the stratum corneum. Prevotella spp. may perform a key role in the vulvar skin of Japanese women.