Oral blood blisters are common in mouth ulcers, in the clinical, often see some people appear recurrent oral blood blisters, season after season, deeply disturbed. In fact, this is not only oral problems, but the embodiment of systemic diseases, especially some immune system diseases, not only in the skin will also damage the mucous membrane, the following conditions are the cause of “recurrent oral ulcers”. 1, genetic factors: If both parents suffer from recurrent mouth ulcers, their children have about 80-90% of the disease, if one of the two parents suffer from this disease, their children have about 50-60% of the disease. 2, virus infection: mouth ulcers generally occur in the spring and autumn season exchange, the general immunity of people with low immunity due to seasonal changes, and the internal environment can not be adjusted in a timely manner, the immune deficiency, the virus will take advantage of this time, causing ulcers. 3, other factors: such as lack of trace elements zinc, iron, folic acid, vitamin B12, malnutrition, etc., can reduce immune function, increasing the likelihood of recurrent mouth ulcers.