Oral ulcers, also known as “mouth sores”, are superficial ulcers that occur on the oral mucosa and can range in size from rice to soybean, round or ovoid, with a concave ulcer surface and surrounding congestion. The ulcers are periodic, recurrent and self-limiting, and they occur on the lips, cheeks and tongue edges. The etiology and causative mechanisms remain unclear. Triggers may be local trauma, stress, food, drugs, altered hormone levels and vitamin or trace element deficiencies. Systemic diseases, genetics, immunity and microorganisms may play an important role in its occurrence and development. Treatment is mainly local and in severe cases systemic treatment is required. Although the exact cause of mouth ulcers is still not completely clear, experts believe that the occurrence of mouth ulcers is the result of a combination of factors. Immunity, genetics and environment may be the “triad of factors” for the development of oral ulcer, that is, genetic background and appropriate environmental factors (including psychoneurological constitution, psychological and behavioral state, life and work and social environment, etc.) can trigger abnormal immune response and the characteristic lesions of oral ulcer. The “dichotomous factor” theory has also been proposed, in which exogenous factors (viruses and bacteria) and endogenous triggers (hormonal changes, psychosomatic factors, nutritional deficiencies, systemic diseases and immune dysfunction) interact to cause the disease. Most doctors believe that mouth ulcers are related to the following factors: 1. Digestive system diseases and dysfunctions. Patients suffering from systemic diseases are prone to mouth ulcers, mainly by affecting the immune system and causing the disease. Oral ulcers are associated with gastric ulcers, duodenal ulcers, ulcerative colitis, restrictive enteritis, hepatitis, etc. Studies have shown that 30-48% of patients with mouth ulcers have digestive disorders such as bloating, diarrhea or constipation. More than 9% of them have peptic ulcers. 2. Endocrine changes. Some female patients tend to occur during menstruation, which may be related to a decrease in the amount of estrogen in the body. Some women have mouth ulcers every time they have their periods or around the time of menstruation, which can only be temporarily relieved by medication and still appear as usual in the next month when they have their periods, with unbearable pain, and at the same time, are often accompanied by annoying symptoms such as dry mouth, irritability, irritability and dry stools. Clinical research has found that the appearance of mouth ulcers during menstruation is mainly due to the increase in the level of progesterone and the decrease in the level of estrogen (progesterone, etc.) in the body. 3, mental factors. Some patients develop the disease under the condition of mental tension, emotional fluctuations, and poor sleep conditions, which may be related to the dysfunction of the vegetative nerves. 4, genetic factors. If both parents suffer from recurrent mouth ulcers, about 80-90% of their children will have the disease, and if one of the two parents has the disease, about 50-60% of their children will have the disease. 5, other factors. Such as lack of trace elements zinc, iron, folic acid, vitamin B12, malnutrition, etc., can reduce the immune function and increase the possibility of recurrent mouth ulcers. Viruses may be the initiating factor of oral ulcers, but no relevant antibodies have been detected in the serum of patients, and no reports of viruses isolated from the lesioned tissue of oral ulcers have been seen. The role of bacteria on oral ulcers has been proposed for many years, and bacteria closely related to oral ulcers include Streptococcus haematobium and Helicobacter pylori. An imbalance in the production and clearance of superoxide radicals in the body, an imbalance in the ratio of thromboxane B2 and 6-ketoprostane and an overall decrease in the level of thromboxane can trigger oral ulcers. Microcirculatory disorders lead to slow blood flow, low blood flow and dilated capillary venous end, resulting in local ischemia and hypoxia, causing mucosal membrane damage and ulcer formation. Zinc, iron and copper deficiencies in the serum are correlated with the occurrence of RAU. Smoking cessation has also been reported to induce mouth ulcers. Sodium 12-alkyl sulfate (SLS), a component of toothpaste, may stimulate the mucosa and induce oral ulcers. 6. Chinese medical etiological mechanism. Complications can be complicated by halitosis, gum redness, chronic pharyngitis, constipation, headache, dizziness, nausea, fatigue, irritability, fever, lymph node enlargement and other systemic symptoms.