Mouth always long ulcers, for recurrent oral ulcers, medically known as recurrent aphthous ulcers, its specific etiology is not clear, there are large individual differences, related research that it is possible with immunity, genetics, the environment, mental factors, vitamin deficiency, and other factors related to the impact of a variety of factors. 1. Abnormalities in cellular immunity and humoral immunity can easily lead to the occurrence of this disease. 2. Studies on the single gene, multiple genes, genetic material and genetic markers of the disease have found that there is a genetic predisposition to its development. 3. Being influenced by social environment and living environment are also factors that induce the disease. 4. Studies have shown that the influence of mental factors such as anxiety, impatience, anger, and excessive mental stress are also important factors in triggering the disease. 5. The lack of certain vitamins in the body, such as folic acid, vitamin B12, etc., also has an impact on the occurrence of this disease. It should be noted that, always long mouth ulcers, it is recommended to go to the hospital for examination to see whether there is a sharp tooth tip or residual roots and crowns and other stimuli caused. Fixed and long-standing mouth ulcers should also be alerted to the occurrence of oral cancer. Therefore, it is necessary to identify the cause and receive standardized treatment.