Patients often drooling should be judged by combining age and basic medical history. Some common causes are: 1, wrong posture: generally sleep on the table, sleep in the side position may appear drooling. 2, open mouth breathing: open mouth breathing can also lead to drooling while sleeping. 3, oral diseases: the temperature and humidity in the human mouth is very suitable for bacterial reproduction, and the teeth are very easy to accumulate food residues. If you do not pay attention to oral hygiene, you may have tooth decay or periodontal disease. These oral diseases may cause drooling when sleeping. Of course, if ulcers occur in the mouth, the pain will also stimulate the secretion of saliva. 4, facial neuritis: our face in the cold or wind, the facial nerve may become inflamed, and then appear to sleep drooling. 5, stroke: if the middle-aged and elderly people appear drooling, crooked corners of the mouth must be taken seriously, it is recommended to go to the hospital to perform head nuclear magnetic examination, to exclude the possibility of cerebral infarction.