The possible reasons why your face has suddenly become darker lately include excessive sun exposure, facial skin diseases, and internal diseases. 1. Excessive sun exposure: when the facial skin is exposed to excessive ultraviolet radiation, melanocytes in the basal layer of the skin in order to protect the skin from further damage, will synthesize more melanin to help protect the skin, which leads to localized melanin pigmentation of the facial skin, appearing in the face of the phenomenon of a sudden darkening. 2. Facial skin disease: a variety of facial skin diseases such as the existence of irregular treatment, care, excessive scratching, repeated delayed and so on, may lead to facial skin localized pigmentation, thus appearing skin suddenly dark phenomenon. Such as: acne, rosacea, chloasma, eczema and other facial skin problems, long-term delayed, repeated episodes may cause facial hyperpigmentation, so that the face becomes dark. 3. Internal diseases: Chronic liver disease, adrenal-related diseases (such as Addison’s disease), chronic kidney disease and other internal diseases will cause metabolic disorders in the body, thus interfering with the metabolism of melanin cells, leading to skin pigmentation, dark color and other symptoms, showing a sudden darkening of the face. In addition, cancer patients may also cause darkening of the face due to malnutrition, chronic consumption, paraneoplastic syndrome, radiotherapy and other reasons. To sum up, it is recommended that patients with sudden darkening of face, especially with other uncomfortable symptoms, should go to the hospital in time to clarify the cause of the disease and standardize the treatment, so as to avoid further aggravation of the disease.