Rotten corners of the mouth mainly imply the following diseases: keratitis, artificial lipitis, photochemical lipitis, herpes gingivostomatitis and other diseases. 1. Keratitis: it is an inflammation that occurs in the corners of the mouth of the upper and lower lips, manifested by flushing and blistering of the corners of the mouth. There are three main categories: dystrophic, which often occurs in patients with malnutrition and lack of B vitamins; coccidioidomycotic, which is mainly caused by streptococcal and staphylococcal infections; and fungal, which is an inflammation of the corners of the mouth caused by fungal infections, and is often accompanied by clinically associated with labial inflammation and lip erosion. 2. Artificial labiitis: often occurs in young women with anxiety symptoms, caused by bad habits such as lip biting and sucking or self-injurious behavior. 3. Photochemical labiitis: a disease triggered by long-term exposure to ultraviolet light, often causing localized skin ulcers and white plaque formation around the mouth. 4. Herpetic gingivostomatitis: is caused by a variety of factors, with limited oral mucosal ulceration, pain as the main feature of inflammation, can be involved in the corners of the mouth, causing “rotting corners of the mouth” symptoms. Rotten corners of the mouth may also be caused by other reasons, when the patient has symptoms, to go to the hospital in time to avoid delaying treatment.