ABSTRACT
PURPOSE: To observe the alteration ultraviolet radiation (UVR) of skin's tolerance after its exposure to the small dose of UVR under the protection of sunscreen. METHODS: Eleven subjects who applied sunscreen were exposed to 0.75 dose minimal persistent pigment darkening (MPPD) and minimal erythema dose (MED) by the Phototherapy Unit for 4 weeks. Each week their MPPDs and MEDs were measured by solar simulator. Meanwhile, SPECTCOLOMETER® and VISIOSCAN VC98® were used to detect the test areas and control areas. RESULTS: The values of MPPD and MED increased significantly after the exposure to UVR. But there were no visible changes on the surface of skin's texture. CONCLUSION: With the protection of sunscreen, the UVR tolerance of skin was greatly increased after the skin's exposure to the small dose UV.