evidence: Everybody needs some sun exposure to produce vitamin D (which helps calcium absorption for stronger and healthier bones). But unprotected exposure to the sun's ultraviolet (UV) rays can cause damage to the skin, eyes, and immune system. It can also cause cancer. There are other contributing factors such as heredity and environment. But sunburn and excessive UV light exposure do damage the skin. This damage can lead to skin cancer or premature skin aging (photoaging). [...] UVB rays cause a much greater risk of skin cancer than UVA. [...] UVA also increases the damaging effects of UVB, including skin cancer and cataracts.