Breathing through the mouth mainly refers to breathing with the mouth open while sleeping at night, and its hazards mainly include affecting appearance, affecting intellectual development, causing diseases and increasing the risk of sudden death. 1. Affecting appearance: breathing with the mouth can lead to the sinking of the tongue, and in the long run, the growth of the chin will be restricted, appearing the phenomenon of retraction, showing the adenoid face. In addition, it can also lead to misalignment of teeth and poor bite. 2. Impact on intellectual development: breathing through the mouth can easily lead to insufficient oxygen intake, especially in the growth and development stage of the child, because of the lack of oxygen will cause mental depression, slow reaction, slow intellectual development and other phenomena. 3. Trigger diseases: when breathing with the mouth open, the air is not filtered and humidified directly into the throat and airway, increasing the chance of infection, which can cause bronchitis, pharyngitis and other diseases. 4. Increase the risk of sudden death: open-mouth breathing is likely to be accompanied by the phenomenon of apnea, which can easily lead to cardiovascular disease, and in severe cases, sudden death can occur. If there is the phenomenon of long-term breathing with the mouth, pay attention to the hospital in a timely manner, under the guidance of the doctor for treatment.