Researchers and dermatologists have varying ideas about the causes of melasma, but there is no clear consensus. However, there are risk factors that could make you more susceptible to this conditions, some of which include the following: sun (UV) exposure, genetics, hormones (e.g., such as during pregnancy), stress, irregular thyroid function, and certain cosmetics and skin care products. Ethnicity is thought to play a major role, as well. If you’re lighter-skinned, you’re less susceptible than individuals with darker skin. If you’re of the following ethnicities, you may be more susceptible to melasma: African/African-American, Middle Eastern, Mediterranean, Indian, Asian, Latin American, or Hispanic.