Some parents observe that other children breathe through their noses, while their own children breathe through their mouths. Whether it is day or night, the mouth is open and the upper and lower lips are not closed together. If you put a thin cotton thread in front of the child’s nostrils, there is almost no airflow in and out of the nasal cavity to blow it. Is this phenomenon normal? The normal passage for human breathing is through the nasal cavity and not through the mouth. In some physiological situations, people will partially use their mouth to breathe, such as when they need more air during exercise, and nasal breathing will be converted to mouth breathing. If, at normal times, breathing through the mouth is abnormal, you need to pay attention! Why does mouth breathing occur? Obstructive diseases of the upper nasal airway are its main cause. Chronic rhinitis, tonsillitis, sinusitis, turbinate hypertrophy, adenoid hypertrophy and nasal tumors can cause obstruction or partial obstruction of the upper nasal airway. Once the nasal airway is blocked, the patient is forced to breathe air through the mouth. What are the dangers of mouth breathing? Normal nasal respiratory function is a guarantee to guide the normal development of the teeth and jaws and the face. Long-term mouth breathing can lead to dental and facial deformities: narrowing of the dental arch, high arch of the palatal lid, protrusion of the upper teeth, recession of the lower jaw, long face, etc. When there is also tonsillar hypertrophy, jaw protrusion may also occur. What should parents do if their child is mouth breathing? At this time, it is necessary to see two doctors as soon as possible: one is an otorhinolaryngologist or a pentatologist to check for obstructive diseases of the upper nasal airway and to treat them thoroughly. The second is an orthodontist for early treatment of dental and facial deformities after removing the cause of the nasal airway obstruction.