Melasma is a common skin condition that causes brown to gray-brown patches on the skin. It commonly appears on the cheeks, nose bridge, forehead, chin, and above the upper lip. It can also appear on other parts of the body that get a lot of sun exposure, like the forearms and neck. Melasma is commonly caused by sun exposure but can be caused by hormonal changes during pregnancy. It is also a lot more common in women than it is in men.