Skin cancers develop due to sunlight exposure induced by

Ultraviolet radiation is of 3 types; UV-A, UV-B and UV-C. • UVA causes melanin oxidation with transient immediate darkening. Repeated exposure to UV radiation cause degenerative changes in elastin and collagen leading to wrinkling increased laxity and a leathery appearance. It is however used therapeutically in PUVA therapy for the management of vitiligo, psoriasis and cutaneous T cell lymphomaQ. • UVB can cause skin damage by formation of reactive oxygen species and formation of pyrimidine dimmers between adjacent pyrimidines on the same DNA strand. The latter can cause double base substitutions in the p53 resulting in the development of skin cancers. So, it is the most dangerous for humans. Exposure to UV rays also induces DNA repair, apoptosis or cell cycle arrest. The absence of this protective mechanism is seen in patients of Xeroderma pigmentosum causing high incidence of skin cancers. • UVC is not reaching earth because it gets filtered by the protective ozone layer.