Melasma is a common acquired increase of pigmentation that occurs exclusively in sun-exposed areas. Brownish in color, it is exacerbated by sun exposure, pregnancy, oral contraceptives, and certain anti-epilepsy drugs.

Melasma is reasonably common, especially in women of child-bearing age. However, up to 10% of cases have been reported in males. While all races are affected, there is a prominence among Latinos and Asians. Melasma is more apparent during and after periods of sun exposure and less obvoius in winter months, when sun exposure is lacking.

Melasma presents itself in one of the three usually symetrical facial patterns. The most common is a centrofacial pattern involving the cheeks, forehead, upper lip, nose, and chin. Less common are the malar pattern, involving the cheeks and nose, and the mandibular pattern, involvong the ramus of the mandible (the side of the cheeks and jawline). Melasma also occurs on the forearms, but this is rare.