Patient description: A 39-year-old man came to the clinic with cough and shortness of breath that was not relieved by his inhaler. He had these symptoms for 5 days during the past 2 weeks. He doubled his oral corticosteroids in the past week. He is a chef with a history of asthma for 3 years, suffering from frequent cough, wheezing, and shortness of breath and chest tightness. The symptoms become more bothersome within 1-2 hours of starting work every day and worsen throughout the work week. His symptoms improve within 1-2 hours outside the workplace. Spirometry was performed revealing a forced expiratory volume in the first second (FEV1) of 63% of the predicted. His past medical history is significant for seasonal allergic rhinitis in the summer. He doesn't smoke or use illicit drugs. His family history is significant for asthma in his father and sister. He currently uses inhaled corticosteroid (ICS) and fluticasone 500 mcg/salmeterol 50 mcg, one puff twice daily.

Clinical trial eligibility criteria: eligible ages (years): 6.0-18.0,  Asthma in Children Age: More than or equal to 6 years old 2. Fulfilling the diagnosis of asthma or cough variant asthma (CVA) based on the guideline of China. 3. The patients cooperated very well with the doctors to perform lung function test. Asthma is defined as fulfilling followings 1-4 or 4 and 5: 1. History of variable respiratory symptoms: wheezing, shortness of breath, chest tightness, and coughing. Symptoms are often worse at night or upon awakening, and often triggered by exercise, laughter, allergens, or cold air, viral infections. 2. At onset, scattered wheeze in the lungs is heard with prolonged expiratory time. 3. The above symptoms and signs were efficient for anti-asthma, or alleviates voluntarily. 4. Exclusive of other diseases with wheezing, shortness of breath, chest tightness, and coughing. 5. If the manifestation is non-typical, fulfilling one of the followings Documented airflow limitation： 1. Positive BD reversibility test: Increase in FEV1 of >12% from baseline, 15 minutes after inhalation of 200-400 μg albuterol; 2. Significantly increased in lung function after anti-inflammatory treatment; 3. Increase in FEV1 of >12%, after 4 to 8 weeks of treatment with inhaled corticosteroids and (or) anti-leukotrienes Positive bronchial challenge test Excessive variability in twice-daily PEF over 2 weeks: Average daily diurnal PEF variability >13%. Cough variant asthma (CVA) is defined as fulfilling following: 1. Cough at least 4 weeks without sputum and wheeze, worsening at night or upon awakening; 2. No symptoms of infection, or no effect on long term antibiotic treatment; 3. The symptoms and signs were efficient for anti-asthma treatment; 4. Exclusive of other diseases causing wheeze; 5. Positive exercise challenge test and (or) average daily diurnal PEF variability >13%; 6. Individual or primary, secondary relatives with allergic history, or positive allergen detection  Subject will be excluded if she or he has one of the following: 1. congenital heart disease; 2. heart failure; 3. liver failure or renal insufficiency; 4. kidney disease; 5. connective tissue disease; 6. immunodeficiency; 7. tumor; 8. a history of hypertension or diabetes mellitus