The causes of adult drooling in sleep include physiological factors (improper sleeping position, etc.) and pathological factors (oral diseases, etc.). As each person’s individual situation is different, it is recommended to go to the hospital for examination to clarify the cause of the disease, and then treat the cause of the disease under the guidance of the doctor. 1. Physiological factors: when people sleep in the same position for a long time, especially when lying on the side, the lower part of the mouth will store excessive secretion, which leads to drooling during sleep. 2. Pathological factors: people suffering from oral diseases (such as periodontitis, oral ulcers, etc.), cerebrovascular diseases (such as cerebral vascular obstruction, brain tumors, etc.) caused by nerve damage, malocclusion and other diseases, will also be drooling during sleep. It is recommended that people change their position appropriately while sleeping, pay attention to oral hygiene, change bad habits, and if necessary, under the guidance of a doctor.