There are several reasons for drooling: 1st, may be physiological reasons, the child salivary gland secretion is more vigorous, while the mouth volume is small, swallowing function can not keep up, resulting in the secretion of saliva can not swallow in time, flow out of the mouth, in addition some children in teething, because of the stimulation of the local nerve, can make saliva secretion increased, resulting in children appear drooling phenomenon. No. 2, may be oral infections, such as gingivitis, herpes stomatitis, herpes pharyngitis, hand, foot and mouth disease, etc., can cause local ulcers in the mouth, often because of oral pain, the affected child is reluctant to swallow, causing increased salivation. The third is some neurological diseases, such as encephalitis, hydrocephalus, bilirubin encephalopathy, etc., which can lead to the phenomenon of drooling in children with backward intellectual development.