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 a few 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.