Coughing is an important defensive reflex of the airway, and the powerful airflow generated during coughing can remove airway mucus and foreign bodies. However, severe coughing can affect life, work, study and sleep and needs to be treated. Coughs are classified as acute coughs of less than 4 weeks and chronic coughs of more than 4 weeks. Dry cough and wet cough. Chronic cough in children is defined as a cough of greater than four weeks with a normal chest X-ray. Common causes of chronic cough in children include cough variant asthma, upper airway cough syndrome, post-infectious cough, gastroesophageal reflux cough, foreign body cough, and cardiac cough.