Dark skin has higher amounts of pigment than lighter skin. Sunlight triggers the body to make more melanin to help protect the skin from the burning rays. This causes the development of a suntan. Birthmarks, freckles, and liver spots are examples of other dark skin marks that are related to melanin levels.
Many factors increase the amount of pigment that can darken skin.
A toxic reaction to the sun can change the skin's color. This may also occur after eating certain foods, using perfume oils, or taking certain drugs such as tetracycline. Seek medical evaluation if you notice changes in your skin such as bleeding, changes in color, new growths, or changes in the shape of moles. Use sunscreen and cover up when in the sun. Stay out of tanning booths, as well, to avoid possible skin damage.