It is usually due to the development of salivary glands and the shallow floor of the mouth in infants and young children.
In adults, if the corners of the mouth are moist and drooling, it is important to be alert for other symptoms, such as facial palsy if there is incomplete closure of one side of the eyes and cheek puffing; cerebrovascular disease for hemiplegia and slurred speech; and tooth decay for tooth pain. If drooling is associated with other systemic symptoms, prompt medical attention should be sought.