Mouth ulcers are generally not contagious, and the etiology of mouth ulcer occurrence is unclear, with significant individual differences. Genetic factors, low immunity, and partiality to food can lead to susceptibility to mouth ulcers. The occurrence of mouth ulcers is also associated with psychoneurological factors, increased stress, poor sleep, anxiety, tension and depression. The occurrence of mouth ulcers is also associated with systemic systemic diseases, and the presence of digestive diseases such as ulcerative colitis predisposes to the development of mouth ulcers. There is no evidence that mouth ulcers are caused by any type of microbial infection, so they are generally not contagious. The symptoms of mouth ulcers should be clarified in time, and appropriate treatment should be taken to avoid delaying the condition.