The specific causes of oral ulcers are still unclear, and are generally believed to be related to genetic factors, immune factors, mental factors, dietary factors, traumatic factors and other factors. 1. Genetic factors: some studies show that about 40% of patients have a family history of mouth ulcers. 2. Immune factors: decreased immunity makes the body susceptible to pathogens, which can cause the occurrence of oral ulcers. 3. Mental factors: mental stress or often irritable, anxious and nervous, etc., the body’s immune function decline, easy to trigger oral ulcers. 4. Dietary factors: vitamins in the body. Such as iron, zinc, folic acid and vitamin B and other nutrients lack, easy to cause mouth ulcers. 5. Traumatic factors: mostly seen in sharp food, such as fish bones, shell seafood, or orthodontic braces can be caused by the physical damage to the oral mucosa, resulting in the occurrence of mouth ulcers.