Breathing through the mouth is professionally called mouth breathing. For adults, because the facial shape has basically been developed, the effect of mouth breathing on the facial shape is relatively small, usually affecting dry mouth and loss of sense of smell. For children, however, because they are growing and developing, their facial shape is constantly changing, so if they keep using mouth breathing, it will indeed cause a certain change in their facial shape. Mouth breathing, because the mouth is not the main organ of breathing, but the auxiliary organ of breathing, we should normally use the nasal cavity to carry out the main gas exchange, not the mouth, if children use mouth breathing for a long time, then it will cause a series of problems. The main problems include malocclusion, such as high arch of the palatal lid, outward protrusion of the maxillary front teeth, narrowing of the maxillary arch, open lips and elongation of the lower third of the face, etc. If a child is found to have mouth breathing, first of all, it is recommended to go to the ENT department to check whether there is any obvious airway obstruction in the ear, nose and throat. After excluding the causes in the ear, nose and throat, the child can go to the dentistry department to apply orthodontic methods to correct the facial shape changes caused by mouth breathing.