Pigmentation is the coloring of a person's skin. In the case of illness or injury, the person's skin may change color, becoming darker (hyperpigmentation) or lighter (hypopigmentation).
Hyperpigmentation in the skin is caused by an increase in melanin, the substance in the body responsible for pigment. The darkened pigment can be diffuse or focal, affecting such areas as the face and the back of the hands. It may be caused by sun damage, inflammation, or other skin injuries, including those related to acne. In addition, certain conditions such as pregnancy or hormonal changes, illness, and some medications may cause hyperpigmentation.
Hypopigmentation in skin is the result of a reduction in melanin production. One example is vitiligo, an autoimmune disorder in which the pigment-producing cells are damaged. Another example is albinism, a rare inherited disorder caused by the absence of an enzyme that produces melanin and results in a complete lack of pigmentation in skin, hair, or eyes. Pigmentation loss may also occur as a result of skin damage from an infection, blisters, burns, or other trauma.