Frequent mouth ulcers are related to immune factors, mental factors, endocrine factors, digestive system diseases and other reasons. 1. Immune factors: if the patient’s cellular immune function declines, T lymphocyte subpopulation imbalance, recurrent mouth ulcers may occur, such as leukemia. 2. Mental factors: some patients are prone to mental dysfunction due to mental tension and emotional excitement, leading to the emergence of oral ulcers. 3. Endocrine factors: bad habits such as staying up late and diabetes uremia, resulting in endocrine disorders can also appear mouth ulcers. 4. Digestive system diseases: such as gastric ulcers, duodenal ulcers and other diseases are easily complicated by oral ulcers. If the patient recurrent mouth ulcers, may also be other diseases of the oral cavity manifestations, it is recommended to the stomatology timely consultation, under the guidance of a professional doctor to clarify the cause of treatment.