Mouth breathing refers to the phenomenon that children cannot shut up and breathe through their mouths when they sleep, which can affect the beauty of their faces in the long run. The main causes of mouth breathing are as follows: 1. nasal diseases: such as rhinitis, turbinate hypertrophy, deviated nasal septum; 2. tonsillar hypertrophy: regular tonsillar inflammation leads to tonsillar hyperplasia; 3. adenoid hyperplasia: blocking the upper respiratory tract. Mouth breathing can lead to high arch of the upper jaw and anterior protrusion of the dental arch to form a sharp round shape, which eventually makes the muscles around the lips loose and affects facial beauty.