Darkening of the corners of the mouth may be related to stomatitis, fixed drug rash, liver disease, and can be removed by medication, laser treatment, or surgical treatment according to the cause of the disease. 1. Keratitis: patients may have long-term redness and swelling of the corners of the mouth, cracking, crusting and other symptoms, repeated episodes will lead to hyperpigmentation of the corners of the mouth, the corners of the mouth black. Erythromycin ointment and acyclovir cream should be used to improve the symptoms and remove the darkening of the corners of the mouth. In severe cases, laser treatment is also available. 2. Fixed drug rash: patients taking certain drugs, the corners of the mouth around the black, dark, you need to stop using the drug that causes the corners of the mouth black, the symptoms can be relieved by themselves. 3. Liver disease: patients with liver disease will impair liver function, the liver’s ability to process melanin decreases, resulting in melanin deposition causing darkening at the corners of the mouth. It is necessary to carry out liver preservation treatment, and in serious cases, surgery is needed. The darkening of the corners of the mouth may also be caused by other reasons, it is recommended that patients go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, and then under the guidance of the doctor for symptomatic treatment.