If children often sleep with their mouths open, they will have some of the following hazards: 1. It will lead to a very dry mouth, because usually breathing through the nose is due to the role of the nasal cavity to moisten the air, while breathing through the mouth will cause local dryness in the mouth, causing excessive evaporation of water, which causes discomfort in children. 2. It will cause abnormal facial development, because some children sleep with their mouths open, mostly due to adenoid The reason why some children sleep with their mouths open is due to adenoidal hypertrophy, which often affects the development of the jaw after sleeping with their mouths open, resulting in an adenoidal face. If it is caused by adenoid hypertrophy, the child can undergo adenoids removal surgery in time.