Children sleeping with their mouths open is not necessarily adenoid hypertrophy, but may also be due to allergic rhinitis, colds, physiological factors and other reasons. 1. Adenoid hypertrophy: Because the adenoids are located in the side wall of the respiratory tract, if hyperplastic lesions occur, they may cause respiratory tract blockage, and the child may experience respiratory effort and other symptoms, resulting in open-mouthed sleep. 2. Allergic rhinitis: If the patient suffers from allergic rhinitis, symptoms such as nasal congestion, sneezing, itching, etc. may occur, leading to the phenomenon of children sleeping with their mouths open. 3. Cold and flu: If the child has an upper respiratory tract infection due to viral or bacterial invasion of the body, symptoms such as nasal congestion, coughing, sneezing, and fatigue may occur, leading to sleeping with the mouth open. 4. Physiological factors: some children sleep with their mouths open due to habit. Children sleep with their mouths open, it is recommended to go to the hospital in time, clear cause and symptomatic treatment.