(1) Recurrent episodes of wheezing, shortness of breath, chest tightness or cough, mostly associated with exposure to allergens, cold air, physical or chemical irritation, viral upper or lower respiratory tract infections, exercise, etc.; (2) Scattered or diffuse expiratory phase dominated croup with prolonged expiratory phase can be heard in both lungs during an attack; (3) Significant efficacy of bronchodilators; (4) Except for wheezing, shortness of breath, chest tightness or cough caused by other diseases (5) For children with atypical symptoms and croup in the lungs, any one of the following bronchodilator tests may be used to assist in the diagnosis if appropriate, and if positive, asthma may be diagnosed: ① rapid-acting β2 agonist nebulizer solution or aerosol inhalation; ② subcutaneous injection of 0.1% epinephrine 0.01 ml/kg (maximum 0.3 ml/time). In children over 5 years of age, if available, peak expiratory flow rate (PEF) or force expiratory volume in the first second (FEV1) can be measured before and after treatment, and a rise of ≥15% after treatment is considered positive. If no croup is heard in the lungs and FEV1 is >75%, a bronchial excitation test can be performed and a positive diagnosis of asthma can be made.