Sleep spitting is still in the normal physiological state, salivary glands secrete saliva into the mouth, and in the awake state, saliva reaches the gastrointestinal tract with swallowing, or when a person is talking, saliva reaches the gastrointestinal tract with swallowing action. During sleep, the swallowing activity is reduced and more saliva is present in the mouth, and many people open their mouths during sleep, so saliva flows out of the mouth. There is also a pathological state, the pylorus is relaxed, the pylorus is relaxed gastric juice refluxed into the mouth, and then spit out, relatively rare. In addition, facial palsy can also cause this symptom.