Mouth ulcers require vigilance. Recurrent mouth ulcers may be leucosis, recurrent aphthous ulcers, but those with fixed ulcer locations may be cancerous, tuberculous ulcers or oral syphilis. 1… Leukoaraiosis: oral ulcers are a common manifestation of leukoaraiosis, if the patient is not timely for the treatment, after which not only oral ulcers, with the aggravation of the disease will also appear a variety of inflammatory lesions in the eye, etc.. 2. Recurrent aphthous ulcers: the most common oral ulcer disease, with periodic recurrence of the characteristics of the ulcer surface with yellow pseudomembrane, surrounded by a red halo band, the central depression, pain is obvious. If the location of the ulcer is fixed, it may also be caused by other diseases, and patients need to be vigilant. These diseases include oral cancer, mucosal ulcers caused by tuberculosis, oral syphilis can also have a similar ulcer manifestation. When patients have frequent mouth ulcers, they should consult a doctor in a timely manner, under the guidance of a professional doctor, to clarify the cause of the disease and then treat it correctly.