There are two reasons why babies have drooling. First, is the physiological drooling. Generally speaking, when the baby grows to 3-4 months, the salivary glands gradually develop and mature, and the secretion of saliva increases, but the function of swallowing is not yet sound, and the function of lip closure and swallowing is not coordinated, so there is often drooling. When the baby grows to 6-7 months old, teething starts and the eruption of teeth will stimulate the nerves in the mouth. At this time, the baby’s salivary glands are also mature, will be a large number of saliva secretion, the drooling situation is more obvious. Generally speaking, the baby’s physiological drooling will disappear quickly with the baby’s growth and development, as long as good care is not necessary to worry about. Second, is pathological drooling, when the baby suffers from certain oral diseases, such as ulcers or herpes in the mouth, pharyngitis, stomatitis, oral and pharyngeal pain, even swallowing saliva will also feel pain, saliva will not be able to swallow normally and constantly flow out. If a baby who normally doesn’t drool a lot, suddenly appears drooling, and accompanied by crying and discomfort, you need to highly suspect pathological drooling, and need to go to the hospital for examination.