The main hazards of sleeping with your mouth open are fatigue, dry throat, adenoid face and so on. 1. Fatigue: sleep with mouth open nose breathing will be suspended, the body lack of oxygen, blood oxygen saturation decreased, the next day easy to fatigue, after a long time may make memory loss, affecting learning and life. 2. Dry throat: Breathing through the mouth, the dust and bacteria in the air can not be filtered through the nasal cavity, which will stimulate the mucous membrane of the pharynx, resulting in dry throat. 3. Adenoid face: sleeping with the mouth open for a long time may also cause teeth misalignment, upper incisor protrusion into buck teeth, tongue root will fall back, lack of expression, resulting in adenoid face. The harm of sleeping with the mouth open is more, if you can not use the nasal cavity to breathe, it is recommended to go to the hospital in time to do the relevant examination and treatment.