The sudden appearance of dark spots on the face may be caused by external stimulation, or it may be the symptomatic manifestation of some diseases, such as chloasma, melanosis, endocrine disorders, etc., and one should consult the doctor in time to find out the cause. 1. External stimulation: Black dark spots may appear due to prolonged exposure of the skin on the face to the external environment, irradiation by ultraviolet rays or stimulation by cosmetics. 2. Melasma: mostly seen in young and middle-aged women, it refers to yellowish-brown or dark-brown pigmentation spots on the face, which are related to certain drugs, hormone levels, neuropsychiatric factors and so on. 3. Melanosis: Melanosis is a kind of pigmentation disease caused by many factors, and it is more common in people who have been exposed to asphalt and petroleum products for a long time. 4. Endocrine disorders: due to long-term late night, insomnia, nervousness, etc., some endocrine glands or cells in the body can not normally secrete hormones, female patients can appear dark, yellow and black patches on the face, usually accompanied by mood changes, obesity, menstrual irregularities, dysmenorrhea, and even infertility and other symptoms. In addition, age spots and other dark spots can also appear on the face, should be timely consultation, improve the relevant examination, by the doctor for appropriate treatment. At the same time, good habits of work and rest and a good state of mind, to ensure adequate sleep, go out and pay attention to sun protection, etc., can promote the recovery of the disease. There are other reasons for the sudden appearance of dark spots on the face, it is recommended to consult a doctor in time to clarify the cause of the disease and treat the symptoms.