Recurrent mouth ulcers may be related to lowered body immunity or to local mechanical irritation. Recurrent mouth ulcers, also known as aphthous ulcers, are a kind of ulcer-like disease that occurs repeatedly in the oral mucosa, with redness, swelling and pain in the mucosal area, which seriously affects normal work and life. The common causes of recurrent mouth ulcers are low immunity of the body, bacteria or viruses take advantage of the situation to cause mouth ulcers, or lack of vitamins or trace elements in the body, commonly caused by vitamin B and vitamin C deficiency. Micronutrient iron deficiency can lead to increased brittleness of the mucous membrane, and accidental biting may lead to mouth ulcers. Recurrent mouth ulcers are also thought to be related to genetic factors. Children of parents who have a high incidence of mouth ulcers are also prone to attacks. Recurrent mouth ulcers may also be related to local irritants. The presence of a crown stump or a sharp tooth tip in the mouth can lead to traumatic ulcers in the oral mucosa. It can be seen that ulcers in the mucosal area coincide with local irritants. This condition needs to be removed from the irritants, otherwise it may cause cancer. Recurrent mouth ulcers are related to immune deficiency, as well as to genetic factors and local irritants.