Melasma is an acquired pigmentary disorder characterized by symmetrical hyperpigmentation spots on the face. Its pathogenesis is complex, with genetic susceptibility, ultraviolet radiation, hormones, thyroid disorders, pregnancy, medications and other factors associated. It occurs in women of reproductive age with Fitzpatrick skin type IV-VI, and the incidence of melasma ranges from 1.5-33.3%. It is also seen in men. 1.Changes in hormone level The incidence rate of pregnant women is around 50-70%. The study of hormone levels in melasma patients found that the patients had significantly higher luteinizing hormone and lower serum estradiol levels, indicating subclinical mild ovarian hypofunction. Thyroid autoimmunity and melasma are significantly associated with each other, especially in women who are pregnant or taking OCPs. 2. Drugs 10% of patients using phenytoin sodium may develop hyperpigmentation similar to melasma. The drug plays a direct role in inducing melanocytes to secrete melanin granules, in addition, it also induces an increase in pigmentation in the basal layer of the epidermis, which can disappear after several months of discontinuing the drug. 3, the role of visible light Studies have found that both UVA and visible light can increase hyperpigmentation, especially for patients with darker skin tones (skin type IV-VI). In addition, visible light is more intense and stable for patients with hyperpigmentation compared to UVA. Studies have shown that visible light can also induce skin hyperpigmentation, suggesting the need for physical sunscreens to prevent the recurrence of melasma.