Ultraviolet (UV) radiation from the sun is the main cause of skin cancer. (Two types of ultraviolet radiation--UVA and UVB--are explained in the ultraviolet (UV) radiation definition in the Dictionary.) Artificial sources of UV radiation, such as sunlamps and tanning booths, can also cause skin cancer.

The risk of developing skin cancer is affected by where a person lives. People who live in areas that get high levels of UV radiation from the sun are more likely to get skin cancer. In the United States, for example, skin cancer is more common in Texas than it is in Minnesota, where the sun is not as strong. Worldwide, the highest rates of skin cancer are found in South Africa and Australia, areas that receive high amounts of UV radiation.

In addition, skin cancer is related to lifetime exposure to UV radiation. Most skin cancers appear after age 50, but the sun's damaging effects begin at an early age. Therefore, protection should start in childhood to prevent skin cancer later in life.