The human skin acts as a physical and immunological barrier to outside toxicants, microorganisms and harmful irradiations. Utraviolet radiation (UV) from the sun might potentially play an active role in regulating several biological events. It has become clear that UV exposure (especially 280-320 nm) can also affect spesific and nonspesific immun responses. Langerhans cells, regulatory T cells, active B cells, mast cells, NKT cells and some mediators, including cis-urocanic acid, serotonin, platelet activating factor (PAF), and nitric oxide (NO) seem to play a crucial role in the induction of UVB-induced immunsupression. IL-10 from keratinocytes, mast cells and supressor B cells is noteworthy as a most important cytokine in the development of immunsupression. UV-induced immunsupression may block antigenic stimulus on the skin, and allow of a balanced apoptosis and DNA repair.