Melasma is a brown pigmentary disorder that primarily appears symmetrically on both cheeks and the forehead; it is caused by pigment cells producing excessive amounts of melanin. Factors contributing to melasma include genetic predisposition, exposure to ultraviolet (UV) and visible light, pregnancy, oral contraceptives, hormonal changes, certain medications and cosmetics, and thyroid disorders. It is most common in women in their 20s to 40s with darker skin tones. Treatment options include a combination of hydroquinone, tretinoin, and topical steroids, or topical agents such as azelaic acid, tranexamic acid, and kojic acid; in some cases, oral tranexamic acid may be considered. Chemical peels and lasers are also used, but caution is advised as they may actually worsen the condition or cause post-inflammatory hyperpigmentation. Above all, melasma can reappear with summer sun exposure, so thorough sun protection—including SPF 50+ sunscreen (such as products containing iron oxide) and a wide-brimmed hat—year-round is key to managing the condition. Since treatment methods and prognosis vary depending on the depth and cause of the pigmentation, a consultation is necessary to determine the appropriate course of action. This information is for reference only and does not constitute a diagnosis. Please consult a specialist regarding actual procedures.
[Source] https://dermnetnz.org/topics/melasma