Melasma or Cholasma or mask of pregnancy is the occurrence of brown patches on the face. Most commonly both sides of the face are affected with involvement of the cheeks, bridge of nose, forehead, and upper lip.

Melasma mostly occurs in adult women and rarely in men. Dark-skinned races, particularly people from the Middle East, and Northern Africa, tend to have Melasma more than others. Up till now, the precise cause of Melasma is unknown.

However family history, skin type, and hormonal changes may be related. It is commonly associated with pregnancy. Birth control pills may also cause Melasma. Sun exposure contributes to Melasma.
Ultraviolet light from the sun, and even very strong light from light bulbs, can stimulate pigment-producing cells or Melanocytes in the skin. Incidental exposure to the sun is mainly the reason for recurrences of Melasma. Any irritation of the skin may cause an increase in pigmentation in dark-skinned individuals, which may also worsen Melasma. Melasma is not associated with any internal diseases or organ malfunction.
Treatment is usually challenging.