Melasma is most common in women between the ages of 20 and 40. It usually affects the cheeks, bridge of the nose, forehead and upper lip. It is most often caused by the hormonal changes or fluctuations that occur during pregnancy, though it can happen at any time. These hormones mean that dark patches are more likely to develop when your skin is exposed to sunlight. Ultraviolet light and even strong light from light bulbs can also stimulate this dark pigmentation. Melasma is more prevalent in darker-skinned races, particularly Hispanic, Asian, Indian and people from the Middle East and Northern Africa. Only 10% of Melasma sufferers are men.