Drooling while sleeping is mainly related to improper sleeping position, malocclusion and facial nerve injury. As each person’s individual situation is different, it is recommended to go to the hospital for further examination to clarify the cause of the disease, and then treat the cause. 1. Improper sleeping position: As a result of sleeping on the side for a long time, excessive accumulation of secretion in the mouth and drooling. 2. Malocclusion: When the upper and lower teeth are not in the same occlusal plane, or when they are too protruding, the upper lip and the lower lip can not be merged together, causing the discomfort of drooling. It is recommended to have orthodontic treatment in a regular hospital. 3. Facial nerves: Some brain diseases (such as cerebrovascular hemorrhage, tumors, etc.) cause neuritis or nerve compression, resulting in drooling in sleep, facial paralysis and other uncomfortable symptoms.