Mouth ulcers in 3-year-old children can be treated with mouth ulcer dispersions, etc. At the same time, irritants in the mouth such as dental caries need to be removed. 1. 3-year-old children with mouth ulcers can use ice boron powder, oral ulcer dispersions, etc., which can adsorb the exudate on the surface of the ulcer, reduce external irritation, and promote wound healing, etc. 2. If there are irritating factors, such as the gap of dental caries, etc., may be friction damage to the internal surface of the mouth, triggering ulcers, so you need to carry out caries repair in time. Normally, it is necessary to pay attention to the diet of light, pay attention to maintain oral hygiene. If the symptoms of mouth ulcers are serious, you should go to the hospital in time for examination, and use the above medicines in accordance with the doctor’s instructions.