Newborns mouth always open may be a normal physiological phenomenon, but also may be related to nasal diseases, need to pay attention to avoid infection, keep the mucous membrane moist, clean up regularly. 1. Physiological phenomenon: newborns mouth is always open, may be a normal physiological situation, need to pay attention to avoid the oral mucosa or respiratory mucosa is too dry, pay attention to open the window to ventilate, maintain air circulation in the house, to reduce the infection of bacteria and so on. 2. Nasal disease: there may be nasal mucosal congestion, edema caused by poor breathing, such as nasal congestion, rhinitis, bronchitis and other diseases, need to open the mouth to assist breathing, attention should be paid to timely cleaning of the nasal cavity, to keep the nasal cavity clean and clear, if the symptoms are serious, it is recommended to seek medical treatment in a timely manner. Newborn baby’s mouth is always open, parents need to take the baby to the doctor in time to clarify the cause.