Cough is a common respiratory symptom caused by inflammation, foreign bodies, physical or chemical irritation of the trachea, bronchial mucosa or pleura, and it has a protective effect of removing foreign bodies and secretions from the respiratory tract. Babies often have a cough that is light during the day and heavy at night, for the following reasons: 1. During the day, due to activity, active breathing, and constant position changes, secretions in the respiratory tract do not easily gather and are easily discharged, and there is relatively little respiratory stimulation, so the cough may be lighter or not cough during the day. At night, with less activity and lower respiratory rate, secretions tend to gather and stimulate the respiratory tract, causing coughing. 2. The temperature difference between day and night. Since the temperature at night is lower than during the day, the cold air stimulates the respiratory tract and causes coughing. 3. After lying down at night, the trachea and bronchi are compressed by the chest wall and the degree of respiratory patency is relatively reduced, which, together with dryness or edema of the respiratory tract caused by infection and other factors, further stimulates the respiratory tract and causes coughing to worsen. The vast majority of coughs are caused by respiratory diseases, so preventing respiratory diseases is the key to cough prevention. Babies need to strengthen their lifestyle regimen, eat appropriately and get enough sleep. Take your child to less crowded public places and open windows frequently to circulate fresh air.