UVA rays are more harmful than UVB rays. They are 100 to 1,000 times more abundant, depending on the season. UVB light only reaches the outer layer of skin, but UVA goes through the inner layer, where it can damage blood vessels, cells that make up the skin's physical support system, and DNA. UVB rays are a major cause of skin cancer.

Although small amounts of UV-B help the body to produce vitamin-D as well as kill some skin diseases such as lupus vulgaris (tuberculosis of the skin) and erysipelas, 1 UV-B is generally damaging to the body. Basal cell carcinoma, the most common form of skin cancer, has recently been linked to a mutated gene that may be caused by excessive exposure to sunlight.2 Closely linked to melanoma skin cancer, UV-B accelerates the aging process of the skin and causes non-melanoma skin cancer most commonly in light-skinned people while suppressing...