With the increase of age and pigmentation on the face, chloasma occurs in many people, especially women. There are very many reasons, including pregnancy factor, drug factor, other factors, etc. The details are as follows: First, pregnancy factor: for example, the increase of androgen and progesterone, after pregnancy, the placenta will secrete the increase of androgen and progesterone, so the pregnant women’s cheeks often appear symmetrical distribution of chloasma, and after the production of the body’s secretion of androgen and progesterone returns to normal, most of the spots can be alleviated or disappeared. Secondly, drug factors: 9%-20% of women who have been taking oral contraceptives for a long time are prone to chloasma, and some of them even have facial spots after taking oral contraceptives for one month. In addition, taking drugs for high blood pressure and diabetes, as well as eating more photosensitive food, etc., can cause chloasma. Thirdly, other factors: for example, chronic diseases, hepatitis and tuberculosis will lead to increased tyrosinase activity and increased melanin production. Therefore, the causes of chloasma are very complicated, and the treatment should start multi-faceted and all-round treatment.