Home > Dermatology > Sun Exposure Get the Flash Player to see this player. Rate: (Click the stars to rate) Published on Aug 10, 2008 by StephenKatz, Views: 2507 Ultraviolet B or UV B causes the most damage to the skin over time. Sun exposure causes skin cancer more commonly in fair skinned people. Basal cell carcinoma is the most common cancer and appears as a small crusty bump which can bleed. Melanoma is less common, but more deadly. It appears as a mole that is irregular, and has multiple colors, and can bleed. Sunscreen, and avoidance of sun will decrease risk of cancer.