Usually, drooling at night may be caused by physiological reasons, or gingivitis, facial nerve palsy and other reasons. 1. Physiological reasons: the patient may be related to the sleeping position, lying down to sleep is more prone to the phenomenon of drooling in bed at night. Generally belongs to the normal physiological phenomenon. 2. Gingivitis: the patient’s gums may be invaded by plaque and inflammatory reaction, under the stimulation and accumulation of inflammatory substances, the gingival sulcus fluid exudation increases, so the patient will be drooling in bed at night. 3. Facial nerve palsy: patients may be paralyzed due to facial nerve damage, resulting in facial muscle paralysis, which leads to crooked corners of the mouth and saliva retention, and therefore also leads to drooling in bed at night. Other causes may also lead to drooling in bed at night, it is recommended to exclude the physiological causes, consult a doctor in a timely manner, and under the guidance of a professional doctor for appropriate treatment.