Darkening of the face may be caused by ultraviolet irradiation, or it may be caused by hepatitis, malnutrition and other diseases. 1. Ultraviolet radiation: If the patient is exposed to the sun for a long time in daily life or work, the ultraviolet rays in the sun will tan or burn the skin, so the patient will have a black and dark face. 2. Hepatitis: Hepatitis is mainly caused by viral, bacterial, parasitic and other pathogen infections, and patients will have symptoms such as itchy skin, darkness and hyperpigmentation. In addition, patients with hepatitis will also experience symptoms such as loss of appetite, diarrhea, nausea and indigestion. 3. Malnutrition: Malnutrition is mainly caused by insufficient intake of nutrients or imbalance in proportion. The main symptoms of patients are skin laxity, yellow hair, muscle atrophy, etc., which will lead to the phenomenon of darkening of the face. When the patient has the symptom of darkening of the face, it may be a normal physiological phenomenon caused by ultraviolet radiation and does not need to be treated. If it is caused by a disease, patients should consult a doctor in time and follow the doctor’s instructions for treatment.