Children breathing through their mouths may be caused by upper respiratory tract infections, may also be caused by allergic rhinitis, and may also be caused by adenoid hypertrophy, the causes are different, the treatment is different. 1. Upper respiratory tract infection: children with upper respiratory tract infection will have nasal congestion, runny nose, which is due to the nasal mucosa congestion and edema, secretion increase caused by this situation due to the nasal cavity is not open, so the children will appear to breathe through the mouth performance. Most viral infections can be self-cured, and bacterial infections can be treated with drugs such as amoxicillin. 2. Allergic rhinitis: Allergic rhinitis is a kind of disease due to the presence of allergens in the environment, which is inhaled by the child through the nasal cavity, and leads to the perverse reaction of the nasal mucosa, and the children with this disease will also have the symptom of breathing through the mouth. Generally away from the allergens can be improved, if the allergy symptoms are serious, the use of loratadine and other drugs for treatment. 3. Adenoid hypertrophy: Adenoid hypertrophy is a disease in which the pharyngeal tonsils become pathologically enlarged due to infection or repeated inflammatory stimulation. The enlarged adenoids can block the posterior nostrils, which can lead to the symptom of children breathing through their mouths. This can be treated surgically. If the symptom of mouth breathing persists in a child, please consult a doctor to identify the cause to avoid delay. The above medications should be used under medical supervision.