Darkening of the face may be caused by physiological factors such as excessive sun exposure, and may also be related to diseases such as melanosis and hepatitis. 1. Physiological factors: If the face is exposed to the sun for a long time, and the face is not well protected when traveling, the stimulation of ultraviolet rays will lead to the secretion of melanin in the face, which will lead to the appearance of darkening of the face. 2. Melanosis: the cause of the disease is not clear, may be related to malnutrition, endocrine disorders and other factors. The damaged skin of patients will appear gray-purple hyperpigmentation patches, mostly in the face. 3. Hepatitis: the cause may be related to infection, alcohol, autoimmune and other factors. Patients will appear liver disease face, cheeks will appear brown pigmentation, the skin will appear dark and lusterless phenomenon. There are more reasons for the darkening of the face, and after excluding physiological factors, it is recommended to go to a regular hospital for consultation and examination to clarify the cause of the disease, so as not to delay the condition.