The hazards of sleeping with your mouth open at night include adenoid facial changes, dry mouth, and affecting sleep quality. 1. Adenoid face change: sleeping at night for a long time open mouth breathing, will lead to changes in lip muscle strength, causing adenoid face change. 2. Dry mouth: when breathing with the mouth open, the air is not moisturized and warmed by the nasal cavity, and it directly enters the mouth, which will lead to the loss of oral moisture and the symptoms of dry mouth. 3. Impact on sleep quality: Sleeping with your mouth open at night will reduce the oxygen content in the blood, and lead to insufficient ventilation in the nasal cavity, which is prone to hypoxia, leading to a decline in the quality of sleep. And it is also easy to have a lack of concentration and drowsiness during the day. If you continue to sleep with your mouth open at night, it is recommended that you seek professional medical intervention to avoid adverse consequences.