When exposed to sunlight, specialized skin cells called melanocytes (see Overview of Skin Pigment Overview of Skin Pigment 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... read more ) produce increased amounts of the pigment melanin, causing the skin to darken, or tan. In some fair-skinned people, certain melanocytes produce more melanin than others in response to sunlight. This uneven melanin production results in spots of pigmentation known as freckles. A tendency to freckle runs in families. Other factors besides sunlight can cause increased melanin in spots or patches (localized) or in widespread areas of skin. Rarely, other substances besides melanin cause darkening of the skin.
Localized hyperpigmentation can be caused by
Reactions to sunlight
Abnormal skin growths
Hyperpigmentation can develop after injuries such as cuts and burns or inflammation caused by disorders such as acne Acne Acne is a common skin condition causing pimples and other abnormalities on the face and upper torso. Acne is caused by a buildup of dead skin cells, bacteria, and dried sebum that blocks the... read more and lupus Systemic Lupus Erythematosus (SLE) Systemic lupus erythematosus is a chronic autoimmune inflammatory connective tissue disorder that can involve joints, kidneys, skin, mucous membranes, and blood vessel walls. Problems in the... read more .
Some people develop hyperpigmentation in areas of skin that have been exposed to sunlight. Some plants (including limes, celery, and parsley) contain compounds called furocoumarins that make some people's skin more sensitive to the effects of ultraviolet light. This reaction is called phytophotodermatitis (see Chemical photosensitivity Chemical photosensitivity Photosensitivity, sometimes referred to as a sun allergy, is an immune system reaction that is triggered by sunlight. Sunlight can trigger immune system reactions. People develop itchy eruptions... read more ).
Hyperpigmentation can also occur in 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 , freckles 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 , 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 café-au-lait spots (flat, brown spots), as well as in abnormal skin growths such as melanoma Melanoma Melanoma is a skin cancer that begins in the pigment-producing cells of the skin (melanocytes). Melanomas can begin on normal skin or in existing moles. They may be irregular, flat or raised... read more .
People who have a disorder called acanthosis nigricans develop darkened and thickened skin in the underarms, on the nape of the neck, and in skinfolds. Acanthosis nigricans can be a symptom of diabetes.
Lentigines (commonly called age spots or liver spots [but are not related to liver problems]) are flat, tan to brown, oval spots on the skin. A single spot is called a lentigo. They are a type of localized hyperpigmentation.
There are two types:
Solar lentigines are caused by sun exposure and are the most common type of lentigo. They occur most frequently on areas that are exposed to the sun, such as the face and back of the hands. They typically first appear during middle age and increase in number as people age. Lentigines are noncancerous (benign), but people who have them may be at higher risk of melanoma.
Nonsolar lentigines are not caused by sun exposure. Nonsolar lentigines sometimes occur in people with certain rare hereditary disorders, such as Peutz-Jeghers syndrome Hereditary conditions that cause intestinal polyps (characterized by many lentigines on the lips and polyps in the stomach and intestine), xeroderma pigmentosum, and multiple lentigines syndrome (LEOPARD syndrome).
If people do not have too many lentigines, doctors can remove them with freezing treatments (cryotherapy) or laser therapy. Bleaching agents such as hydroquinone are not effective.
Widespread hyperpigmentation can be caused by
Changes in hormones
Drugs and heavy metals
Hormonal changes may increase melanin production and darken the skin in Addison disease Adrenal Insufficiency In adrenal insufficiency, the adrenal glands do not produce enough adrenal hormones. Adrenal insufficiency may be caused by a disorder of the adrenal glands, a disorder of the pituitary gland... read more , in pregnancy, or with hormonal contraceptive use. A liver disorder called primary biliary cholangitis Primary Biliary Cholangitis (PBC) Primary biliary cholangitis (PBC) is inflammation with progressive scarring of the bile ducts in the liver. Eventually, the ducts are blocked, the liver becomes scarred, and cirrhosis and liver... read more (previously called primary biliary cirrhosis) may also cause increased melanin production.
Some cases of hyperpigmentation are caused not by melanin but by other pigmented substances that are not normally present in the skin. Diseases such as hemochromatosis Hemochromatosis Hemochromatosis is a hereditary disorder that causes the body to absorb too much iron, causing iron to build up in the body and damage organs. In the United States, over 1 million people have... read more or hemosiderosis Hemosiderosis Hemosiderosis is a term used for excessive accumulation of iron deposits called hemosiderin in the tissues. (See also Overview of Iron Overload.) The lungs and kidneys are often sites of hemosiderosis... read more , which are caused by too much iron in the body, can cause hyperpigmentation. Some drugs and metals that are applied to the skin, swallowed, or injected can cause hyperpigmentation.
Hyperpigmentation caused by drugs and heavy metals
Drugs and heavy metals that can cause hyperpigmentation include the following:
Some cancer chemotherapy drugs
Some tricyclic antidepressants
Some heavy metals (such as silver, gold, and mercury, which can be poisonous)
The areas of hyperpigmentation are usually widespread, but some drugs can specifically affect certain areas. For example, some people develop fixed drug reactions, in which certain drugs (for example, certain antibiotics, nonsteroidal anti-inflammatory drugs [NSAIDs], and barbiturates) cause red patches or blisters to form in the same place on the skin every time the drug is taken. These reactions eventually lead to hyperpigmentation of the affected skin.
Depending on the drug or metal and where it is concentrated in the skin, hyperpigmentation may be violet, bluish black, yellow-brown, or shades of blue, silver, and gray (see also Color Changes in the Skin Color Changes in the Skin Doctors use specific terms to describe various types of marks and growths on the skin. Some skin disorders and infections can cause color changes in the skin. (See also Structure and Function... read more ). In addition to the skin, the teeth, nails, white of the eyes (sclera), and lining of the mouth (mucosa) may be discolored. With many of these drugs, the hyperpigmentation often fades after the drug is stopped, but it can take longer to fade in people who have darker skin. Sometimes the hyperpigmentation is permanent regardless of skin color.
Because many drugs that cause skin pigmentation also cause photosensitivity reactions Photosensitivity Reactions Photosensitivity, sometimes referred to as a sun allergy, is an immune system reaction that is triggered by sunlight. Sunlight can trigger immune system reactions. People develop itchy eruptions... read more , people should avoid the sun Avoidance Sunburn results from a brief (acute) overexposure to ultraviolet (UV) light. Overexposure to ultraviolet light causes sunburn. Sunburn causes painful reddened skin and sometimes blisters, fever... read more .