A suntan is a darkening of the skin in reaction to exposure to the
ultraviolet (UV) rays in sunlight. The skin pigment melanin becomes darker as
UV rays damage the skin.
Although skin gets darker to protect its deepest layers against
harm from UV rays, a tan is evidence of some degree of sun damage. This damage
is cumulative, which means the more time a person spends in the sun over many
years, the more long-term damage is done to the skin.
Tanning booths also can cause skin changes and damage.