Drooling in bed can be triggered mainly because of the sleeping position or the use of some medications. The body produces more than one liter of saliva every day, and saliva produced by salivary glands enters the digestive system mainly through swallowing. When saliva appears in the mouth without being swallowed, drooling occurs. Incorrect sleep posture can make the mouth is open, and when the mouth is open during sleep, saliva is not swallowed but flows out of the mouth. The biggest reason why the mouth is open at night is that it cannot breathe through the nose, and it happens that saliva flows out of the mouth during sleep, so snoring and sleep apnea may be strongly related to drooling, and in addition, excessive drooling may be caused by the use of some medications. This type of disorder may be secondary to brain injury, stroke or even Parkinson’s disease such as dysphagia. Most of such conditions manifest during the daytime. The main cause of drooling in bed is related to the opening of the mouth during sleep at night, so improving the sleep position may alleviate this problem. If it is related to other diseases, it is important to seek medical attention and the doctor will make the most suitable treatment plan according to the patient’s disease condition.