ABSTRACT
The acute effects of ultraviolet radiation (UVR) on the skin comprise a range of responses, many of which are harmful in the short term or after cumulative exposure in the longer term, and others that are beneficial. Ultraviolet-A and -B reach the earth’s surface and both can cause acute effects on human skin. The shorter wavelength UVB is more potent in causing several acute effects of UVR, and the action spectrum for various acute effects of UVR varies from UVB alone, to UVA alone, to a combination of both wavebands. UVR activates cell membrane phospholipase A2, releasing arachidonic acid that is then used to synthesize mediators of the eicosanoid family. UVR-induced skin pigmentation occurs in three distinct phases; that is, immediate pigment darkening, persistent pigment darkening, and delayed tanning. Tanning occurs as a response to UVR-induced damage of the skin and may serve to limit the amount of subsequent damage caused by continued UVR exposure.
