Sairei-to, a traditional Japanese herbal medicine, inhibits UVB-induced skin inflammation

[Introduction] Ultraviolet (UV) radiation, especially UVB (280-320 nm) from sunlight, is one of major environmental hazard to induce skin damage. A single high dose UVB exposure on the skin causes the acute inflammatory reaction which is characterized by erythema, increasing vascular permeability and edema formation. The single UVB-induced damage could be accumulated by chronic UVB irradiation. The accumulated skin damage could lead to skin aging and raise the risk of skin cancer. Therefore, the inhibition of single UVB-induced acute inflammation is important target for protecting skin from UVB exposure. Sairei-to (SRT), a traditional Japanese herbal medicine, has been used for inflammation treatment. Recently, it has been clinically evidenced to inhibit edema formation caused by radiotherapy. However, the effect of SRT on UVB-induced skin inflammation is poorly understood. In this study, we investigated the protective effect of SRT against the acute UVB-induced skin damage in hairless mice.