Melasma is a common skin condition that causes brown to gray-brown patches which usually appear on the face. The cheeks, bridge of nose, forehead, chin and upper lip are places where melasma is likely to form. It can also develop on the forearms and neck. Most melasma occurs in women. Only 10 percent of those affected are men. People with darker skin tones, including those of Latin, Asian, Indian, Middle Eastern and Mediterranean descent tend to have melasma more than others.

Pregnancy, birth control pills, cosmetics, hormone therapy, certain drugs (which make the skin more susceptible to light damage), anti-seizure medication and sun exposure often trigger melasma. Melasma is so common during pregnancy that it is often called chloasma, or the “mask of pregnancy”. Sun exposure can trigger melasma because the pigment-producing cells in the skin (melanocytes) are stimulated by ultraviolet (UV) light from the sun. People with skin of color have more active melanocytes than those with light skin so they produce more pigment. This production increases when stimulated by light exposure or rising hormone levels. It only takes a small amount of sun exposure for melasma to return after fading.