Brief overexposure causes sunburn.
Melanin, a naturally protective substance, absorbs the energy of ultraviolet rays and prevents the rays from penetrating deeper into the tissues. Sensitivity to sunlight varies according to race, previous exposure, and complexion, but everyone is vulnerable to some extent. Because dark-skinned people have more melanin, they have more resistance to the sun's harmful effects, which include sunburn, premature aging of the skin, and skin cancer. Albinos have no melanin in their skin, can't tan at all, and burn severely with even a little sun exposure. Unless albinos protect themselves from the sun, they develop skin cancers at an early age.