Children with mouth ulcers are mostly caused by the lack of vitamin C and vitamin B₂, you can eat more food rich in vitamin C and vitamin B₂ food in life. 1. Foods rich in vitamin C: In life, you can let the children eat some fruits such as watermelon, bananas, kiwi, oranges, dragon fruit and other more digestible and easy to absorb fruits, you can also drink some apple juice, lemonade and so on. 2. Foods rich in vitamin B₂: Vitamin B₂, also known as riboflavin, is a water-soluble vitamin is also involved in the metabolic physiological process of cell growth, for mucous membranes, the skin has an important repair function, can be supplemented through the food, such as animal offal, eggs, soybeans and other foods for dietary supplements. At the same time, we should also pay attention to oral hygiene, brush your teeth after meals can effectively avoid the breeding of oral bacteria, avoid spicy food, mainly to light, mouth ulcers should be serious under the guidance of the doctor for medication.