Mouth ulcers may be caused by dietary factors, mechanical injury, infection and other reasons. 1. Dietary factors: it may be due to eating too hot, irritating, spicy and other foods, which stimulate the oral mucosa, thus appearing the phenomenon of mouth ulcers. 2. Mechanical injury: such as food in the fish bone, toothbrush, dental surface deposits of dental calculus, bite and other phenomena, can be direct or chronic damage to the oral mucosa, thus appearing in the mouth with the phenomenon of ulcers. 3. Infection: may be due to infection with bacteria, viruses and other pathogenic bacteria. Cells can produce viral and bacterial antigens and thus the immune response, which can cause pathological changes in the host tissue and the formation of ulcers, and then the phenomenon of mouth ulcers. In addition, vitamin deficiencies and other causes can also cause mouth ulcers. General ulcers are not serious patients can be temporarily observed, most can be self-healing. If the ulcers are serious, it is recommended to go to the hospital in a timely manner, and follow the doctor’s instructions for treatment to avoid delaying the condition.