Skin tone depends on the amount of pigment or melanin that is present in the skin. 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. Some causes are:
* Skin irritation from acne, dermatitis, allergy, or infection.
* Skin damage from burning or freezing such as medical treatments with liquid nitrogen or chemical peels.
* Changes in hormone levels due to pregnancy, an over-active thyroid, or taking birth control pills.
* High levels of iron or beta-carotene in the body.
* Injections of metals that contain pigment, as in gold shots that are given for arthritis treatment.
* Diseases such as Addison's disease, diabetes, and anemia.

Exposure to ultraviolet light or sunlight can be harmful. A phototoxic reaction to the sun can change the skin's color. This may also occur after eating certain foods (citrus fruits and celery) , using perfume oils, or taking certain drugs such as tetracycline.

Seek medical evaluation if you notice changes in your skin such as changes in color, new growths, changes in the shape of moles, or bleeding. Use sunscreen and cover up when in the sun. Stay out of tanning booths as well to avoid possible skin damage.

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