Skin cancer almost never occurs on the buttocks, under the arms or on the inner thighs. The skin has several defense systems to help protect it from ultraviolet rays. The most important of these is the pigment or color of the skin. The skin is made of building blocks called cells. One type of skin cell, the melanocyte, produces a chemical called melanin.
Melanin is a chemical or pigment which determines the color of the skin.
Both blacks and whites have the same number of melanocytes, but in blacks, the melanocytes produce larger globules of pigment which causes their skin to be darker. The skin color or melanin protects the skin from the harmful effects of ultraviolet light. The extra melanin or color in an African-American's skin is equivalent to a white person wearing a sunscreen with an SPF of 45. Most black people look ten years younger than their white counterparts because of this increased protection. When the skin is exposed to ultraviolet light, it is injured and responds by making more color or melanin.