Melasma is most likely caused by an overproduction of the pigment melanin. Melanin is produced by specialized skin cells called melanocytes (see Overview of Skin Pigment).
Too much pigment in the skin is called hyperpigmentation. Melasma tends to appear during pregnancy (called the mask of pregnancy) and in women who take oral contraceptives, but it can occur in anyone. The disorder is most common among and lasts longer in people with dark skin. Ten percent of cases occur in women who are not pregnant and in dark-skinned men.
People who spend a lot of time in the sun are at increased risk of melasma. Other risk factors include autoimmune thyroid disorders and drugs that make some people's skin more sensitive to the effects of sunlight.
Irregular, patchy areas of dark color appear on the skin, usually on both sides of the face. The pigmentation most often occurs in the center of the face and on the cheeks, forehead, temples, upper lip, and nose. Sometimes people have the patches only on the sides of the face. Rarely, melasma appears on the forearms. The patches do not itch or hurt and are only of cosmetic concern.
Doctors base the diagnosis of melasma on an examination of the skin.
Doctors may do a Wood light examination to differentiate hyperpigmentation in the upper layers of the skin from other skin disorders.
Treatments applied to the skin are effective only if hyperpigmentation affects the upper layers of the skin. Skin-bleaching creams containing hydroquinone, tretinoin, or a corticosteroid can be used in combination to help lighten the dark patches. Hydroquinone should be used only under the guidance of a doctor, because long-term use can actually cause permanent hyperpigmentation. A cream containing azelaic acid can be used in place of or combined with hydroquinone, tretinoin, or both.
Doctors may try chemical peels with glycolic acid or trichloroacetic acid on people who do not respond to skin-bleaching creams.
Laser treatments and tranexamic acid, which is a drug taken by mouth, are also used.
During and after treatment, people must be strict about sun protection because treatments make the skin prone to sunburn. Also, even a few hours of sun exposure can cause hyperpigmentation to begin again in the treated areas, which would undo the results of months of treatment.
If the skin is protected from the sun, melasma often fades after pregnancy or after an oral contraceptive is stopped. In men, melasma rarely fades.