Sunburn is damage to the skin resulting from excessive exposure to the sun’s ultraviolet rays. Depending on the strength of these rays and the degree of skin pigmentation, sunburn to unprotected skin can occur with as little as a few minutes or as long as several hours of exposure. Unlike other types of burn, sunburn is not fully apparent until hours after exposure. Severe sunburn should be evaluated and treated by a doctor. Frequent sunburn contributes to wrinkling and aging of the skin and increases the risk of skin cancer.