Melasma is a difficult-to-treat pigmented skin disease with complex etiology involving endocrine, sun exposure, heredity, chronic diseases, drugs, mental and improper skin care methods. Endocrine factors: elevated estrogen level is one of the main causes of chloasma, commonly found in pregnant women, unmarried women and those taking oral contraceptives. Sunlight exposure: UV, visible and infrared light can increase tyrosinase activity, leading to increased melanin synthesis. Genetic factors: Some scholars have found that the family incidence of melasma is more than 50%, suggesting that the disease has a certain genetic correlation, especially in male patients. Chronic diseases: Many patients suffer from liver diseases, autoimmune thyroid diseases, chronic ethanol poisoning, tuberculosis, female reproductive organ diseases, menstrual disorders, dysmenorrhea, uterine adnexitis, infertility, etc. Drug factors: birth control pills, chlorpromazine, phenytoin, and Antiseptic, etc. Mental factors: mental tension, mood swings, stress, long-term late night and irregular life are prone to chloasma. Improper skin care methods: over-cleaning the skin, using unqualified skin care products that directly damage or stimulate the skin, going to informal institutions to exfoliate, etc. In addition to the above-mentioned reasons, factors such as vascular proliferation and expansion, destruction of skin barrier function and aging of dermal collagen can also lead to the increase of tyrosinase activity, resulting in the appearance of chloasma.