Recurrent mouth ulcers may be a sign of low immunity or a manifestation of systemic diseases in the mouth. Mouth ulcers are autoimmune diseases that occur when staying up late for a long time, stressing, or eating irregularly, and can be improved by physical exercise or oral immunity-enhancing drugs. Mouth ulcers are not a single disease, they are the expression of systemic diseases in the mouth. Gastric ulcers, duodenal ulcers, liver and gallbladder diseases, leukemia, etc. can cause mouth ulcers. A systemic systemic examination and active treatment of the primary disease are needed. Therefore, recurrent mouth ulcers may be caused by decreased immunity, or they may be related to gastric ulcers, leukocele, etc. Further examination is needed, and you can go to the stomatology department or the gastroenterology department.