Sleeping with the mouth open can occur at any age, mostly due to nasal breathing or pharyngeal narrowing and other structural abnormalities caused by common diseases such as rhinitis, adenoid hypertrophy, obstructive sleep apnea syndrome, etc. Sleeping with the mouth open often affects the development of the teeth, facial development, sleep, and sleep, and if sleep apnea hypopnea syndrome, it can lead to multi-systemic damage, and is prone to sudden death during the night. 1. Impact on dental development: long-term open-mouth breathing can easily lead to front teeth protruding outward, and there will be uneven alignment of the teeth, or even misalignment of the teeth, but also easy to inhale a large number of bacteria, which can lead to oral diseases, such as gingivitis; 2. affecting facial development: pediatric patients are prone to jawbone development deformities, thus affecting facial development, and even the formation of adenoid face; 3. affect the mucous membrane of the throat: sleeping with the mouth open will lead to inhalation of air, directly into the throat area, the air is not warmed and humidified, it will lead to dry mucous membrane of the throat, and over time it is easy to form chronic pharyngitis. 4. In case of sleep apnea hypoventilation syndrome, drowsiness and other symptoms may occur. Gradual development of the disease can appear hypertension, arrhythmia, cerebrovascular accident and other serious complications. If you sleep with your mouth open for a long time, you must go to the hospital in time, do a detailed examination, clarify the cause, and then take treatment for the cause to avoid the harm from getting worse.