Generally speaking, most mouth ulcers in children are caused by diet, climate and lack of attention to oral hygiene. If a child’s diet is too fine, he or she may become paranoid, which may lead to vitamin deficiencies, and the dry climate may also cause mouth ulcers. Therefore, it is recommended that children pay attention to B vitamin supplements during the growth and development process, pay attention to a balanced diet and help children to maintain good oral hygiene.