Breathing through the mouth, may be the nasal cavity obstruction, the mouth for compensatory breathing, seen in nasal polyps, adenoid hypertrophy, tonsil hypertrophy and other diseases. 1. Nasal polyps: Nasal polyps are swellings produced by the thickening and extreme edema of the nasal mucosa. These diseases can lead to the ventilation and drainage function of the nasal cavity, thus affecting breathing. The condition can be clarified by nasal endoscopy and CT scanning of the nose. 2. Adenoid hypertrophy is a common cause of mouth breathing in children, which can lead to dysfunction of the ventilation and drainage of the nasopharynx and lead to dyspnea, and the condition can be clarified through nasopharyngeal X-ray or nasopharyngoscopy. 3. Tonsillar hypertrophy will lead to narrowing of the oropharynx and affect the ventilation of the upper airway, thus expanding the pharyngeal cavity by opening the mouth, which is manifested as breathing through the mouth, and tonsillar hypertrophy in the oropharynx will be obvious during the examination. If you have any of the above conditions, you need to consult an ENT doctor to clarify the cause of the disease and follow the doctor’s instructions for treatment.