Cough variant asthma (CVA): CVA is one of the common causes of chronic cough in children, especially in preschool and school-age children. The clinical features and diagnostic clues of CVA are: (1) persistent cough >4 weeks, often at night and/or early in the morning, aggravated by exercise and cold air, without clinical signs of infection or after prolonged antibiotic treatment; (2) diagnostic treatment with bronchodilators results in significant relief of cough symptoms; (3) normal pulmonary ventilation and bronchial excitation tests suggest airway hyperresponsiveness; (4) A history of allergic disease including drug allergy, and a positive family history of allergic disease. (4) History of allergic diseases including drug allergy and positive family history of allergic diseases. A positive allergen test may assist in the diagnosis; (5) Chronic cough caused by other diseases are excluded.