The causes of toothache in children are as follows: 1. If pulpitis is not treated in time and the infection continues to develop deeper along the root of the tooth, it will spread to the alveolar bone around the root, and then the child will not only have pain, but also severe jaw and facial swelling. These are some of the most common causes of toothache, and if this happens, parents should take their children to the hospital promptly for medical attention. In addition to these cases, there are several rare cases, one is that if the oral hygiene of the child is not good during the process of teething, there may be inflammation of the gums around the erupting teeth, and the child will also have pain at this time, but the symptoms of this pain are often not very obvious, and will be eliminated after brushing the teeth.