The corners of the mouth always rot is a symptom of xerostomia, and the main clinical causes are vitamin deficiency malnutrition, or secondary to diabetes mellitus or abnormalities in immune function, which may lead to recurrent xerostomia. This can be symptomatic treatment, you can apply antibiotics for local application, and then for systemic malnutrition, you can supplement vitamin B or treat diabetes, improve the immune function abnormality. This has an excellent therapeutic effect on xerostomia. There are also corns of the mouth may be due to infection or trauma, this situation is generally less recurrent after healing, so if the corners of the mouth are always ulcerated, or consider that there is a relationship with malnutrition, you can go to the hospital for examination, and then carry out the corresponding treatment.