It is especially common in pregnant women, those on oral contraceptives, and hormone replacement
therapy during menopause. It can sometimes occur in males as well. Other medications, such as anti-seizure medications, may also cause melasma. The rash is usually symmetrical and present on the cheeks, lips (including upper lips), nose or the forehead. Sun exposure is strongly associated with melasma.
The best treatment for melasma is prevention. It is good that you are using regular sunscreen.