Melanin is the pigment that produces the various shades and colors of human skin, hair, and eyes. Coloration (pigmentation) is determined by the amount of melanin in the skin. Without melanin, the skin would be pale white with shades of pink caused by blood flow through the skin. Fair-skinned people produce very little melanin, darker-skinned people produce moderate amounts, and very dark-skinned people produce the most. People with albinism Albinism Albinism is a rare hereditary disorder in which little or none of the skin pigment melanin is formed. The skin, hair, and eyes, or sometimes just the eyes, are affected. Typically, the hair... read more have little or no melanin and thus their skin appears white or pale pink. Usually, melanin is fairly evenly distributed in the skin, but sometimes people have spots or patches of skin with more melanin. Examples of such spots include freckles, age spots (lentigines Lentigines Hyperpigmentation is darkening of skin, most often caused by an abnormally high amount of the skin pigment melanin. When exposed to sunlight, specialized skin cells called melanocytes (see Overview... read more ), and melasma Melasma Melasma is dark brown patches of pigmentation that appear on sun-exposed areas of the skin, usually the face. Patchy areas of dark color appear on the skin. Doctors usually base the diagnosis... read more .
Melanin is produced by specialized cells (melanocytes) that are scattered among the other cells in the deepest layer of the outer layer of the skin called the basal layer. After melanin is produced, it spreads into other nearby skin cells.
Pigment disorders can be widespread and affect many areas of skin, or they can be localized and affect only certain areas of the skin. The pigmentation changes they cause are called
Depigmentation is complete loss of pigment. The skin is white. Widespread depigmentation occurs in vitiligo Vitiligo Vitiligo is a loss of melanocytes that causes patches of skin to turn white. Patches of whitened skin are present on various parts of the body. Doctors usually base the diagnosis on the appearance... read more .
Hypopigmentation is an abnormally low amount of melanin. The skin is lighter in color than normal. Widespread hypopigmentation of the skin occurs in albinism Albinism Albinism is a rare hereditary disorder in which little or none of the skin pigment melanin is formed. The skin, hair, and eyes, or sometimes just the eyes, are affected. Typically, the hair... read more .
Hypopigmentation can be caused by
Previous injury to the skin, such as a blister, ulcer, burn, exposure to a chemical, or skin infection
Inflammatory conditions of the skin that have healed (such as atopic dermatitis Atopic Dermatitis (Eczema) Atopic dermatitis (commonly referred to as eczema) is chronic, itchy inflammation of the upper layers of the skin that often develops in people who have hay fever or asthma and in people who... read more or psoriasis Psoriasis Psoriasis is a chronic, recurring disease that causes one or more raised, red patches that have silvery scales and a distinct border between the patch and normal skin. A problem with the immune... read more )
Rare hereditary conditions
Hyperpigmentation Hyperpigmentation Hyperpigmentation is darkening of skin, most often caused by an abnormally high amount of the skin pigment melanin. When exposed to sunlight, specialized skin cells called melanocytes (see Overview... read more is usually caused by an abnormally high amount of melanin, but sometimes it is caused by deposition of other pigmented substances that are not normally present in the skin. The skin is darker in color and sometimes is a different color than normal. Hyperpigmentation can be caused by
Disorders that cause inflammation
Exposure to sunlight