Recurrent mouth ulcers in children may be related to dietary factors, nutritional deficiencies, and immunologic factors. 1. Dietary factors: some recurrent mouth ulcers occur with the consumption of irritating foods, such as spicy or acidic foods, including chili peppers and peppercorns. Or allergic reaction of oral mucosa caused by food allergy. 2. Nutritional deficiencies: lack of zinc, iron, selenium and other elements in food. Or insufficient intake of B vitamins and folic acid can lead to recurrent mouth ulcers. 3. Immune factors: the occurrence of recurrent mouth ulcers is closely related to the body’s immune response. For example, suffering from celiac disease, leucosis, AIDS and other diseases, can cause the body’s allergies, inflammation, immunity decline, resulting in recurrent mouth ulcers. Repeated mouth ulcers in children can also be seen in other causes, it is recommended to consult a doctor in a timely manner, follow the doctor’s instructions to carry out relevant examinations, with the help of the doctor to clarify the cause, and to carry out targeted treatment or therapy.