It is also well known that UVB radiation can induce keratinocytes to synthesize cytokines such as interleukin-1, tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-alpha (TGF-alpha) and nerve growth factor, and also arachidonic acid and its metabolites and all the stimulating factors and cofactors of fibroblast proliferation that are possibly related to melanocyte metabolic turnov