The main reasons for long spots on both sides of cheeks are as follows: a. Genetic factors. Some patients have family history. Second, pregnancy. Chloasma can be caused after pregnancy, which may be related to the increase of estrogen level after pregnancy. Third, caused by diseases. Diseases such as menstrual disorders, uterine fibroids, ovarian cysts and liver and kidney insufficiency can easily cause chloasma. Sun exposure. Frequent exposure to the sun will easily cause chloasma. External use of corticosteroids. Frequent use of hormone ointment on the face will easily cause dark spots. Sixth, other factors. For example, oral contraceptives, external cosmetics, frequent staying up late, alcoholism, etc.