A sunburn is a kind of burn that happens when skin is exposed to sunlight for too long. This makes the skin become red. A sunburn can be painful. Sunburns stay for days or weeks. People with lighter skin have more sunburns than people with darker skin. This is because of a dark pigment called melanin that protects the skin. There is more of it in dark-skinned people than in light-skinned people. Eventually, if exposed to too much sunlight, skin cancer may develop.