The redness, soreness, itching, and sometimes blistering that occurs with sunburn results from too much exposure to the ultraviolet, or UV, rays of the sun or a sunlamp. To prevent sunburn, use sunscreen with a sun protection factor, or SPF, of 15 or greater. Sunscreens differ, so use one that protects against both UVA and UVB rays. Sunburn has many harmful effects including long-term skin damage and increased risk of skin cancer. Even without sunburn, too much sun leads to faster skin aging with wrinkles, sagging, and brown sunspots.