Children’s mouth ulcers may be caused by herpes virus infection, inadequate oral cleaning, lack of trace elements and other reasons. 1. Herpes virus infection: Herpes virus infection is mainly due to the decline in resistance and other factors can lead to herpes virus infection, triggering mouth ulcers herpes and other conditions. 2. Oral cleaning is not in place: children’s oral cleaning is not in place, the mouth will breed a lot of bacteria, so it will lead to mouth ulcers. 3. lack of trace elements: lack of iron, zinc and other trace elements can also lead to mouth ulcers. Children’s mouth ulcers may also have other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.