Mouth breathing, generally referred to as open-mouth breathing, is the need to breathe through the mouth due to the insufficient amount of air entering through the nose. Open mouth breathing may cause abnormal bone development, snoring, affecting sleep quality and other hazards. 1. Abnormal bone development: When breathing with the mouth open, the airflow will impact the hard palate, which will deform and arch the hard palate, causing the upper lip to curl up and the face to change. Long-term open-mouth breathing can also lead to underdevelopment of the lower jaw, which is characterized by a retracted chin. 2. Cause snoring: open mouth breathing may cause snoring. Snoring will lead to lack of oxygen to the brain. 3. Affecting the quality of sleep: daytime dozing, lack of concentration, and even serious intellectual ability will be slightly affected. In addition to the above, open-mouth breathing can also lead to teeth misalignment, bad bite and other reasons. When prolonged open-mouth breathing is accompanied by other discomforts, it is recommended to consult a doctor for further examination and clarification of the causes, such as nasal obstruction, adenoid hypertrophy, sleep apnea syndrome, etc., with the help of the doctor, and to carry out targeted treatment.