The main causes of drooling in sleep include improper sleeping position, inflammation and infection in the mouth, malocclusion and other reasons. It is recommended to go to the hospital for further examination to clarify the cause of the disease and treat the cause. 1. Improper sleeping position: When you sleep at night, it is easy to drool when you keep the same position for a long time and do not change it. 2. Oral inflammation factors: when the mouth is infected by bacteria, triggering gingivitis, periodontitis and other diseases, the secretion of fluid increases, and drooling will occur. 3. Dental malformation: When the front teeth cannot bite properly, the upper and lower lips cannot close and drooling will become more frequent. It is recommended to be corrected under the guidance of a professional dentist. Avoid delaying the best treatment time. Prolonged sleep drooling, should be timely medical treatment.