Patient description: The patient is a 15-year-old boy with asthma diagnosed a year ago. He presents with shortness of breath, chest tightening and cough. According to his mother, he didn't respond to the usual corticosteroid inhaler. He was admitted to the emergency department with diagnosis of severe asthma exacerbation. He is a candidate for general corticosteroid therapy. Spirometry revealed a forced expiratory volume in the first second (FEV1) of 60% of the predicted. His past medical history is non-significant. His family history is significant for asthma in his mother and his uncle. He used to be treated with combination of inhaled corticosteroids and Zafirlukast.

Clinical trial eligibility criteria: eligible ages (years): 18.0-65.0,  Asthmatic Bronchitis The patients with classic asthma Asthmatic patient 1. Male or female patients aged ≥ 18 and ≤ 65, who have signed an Informed Consent form prior to initiation of any study-related procedure. 2. The patients with classic asthma had a history of episode dyspnea and wheezing with or without cough. 3. Clinical diagnosis of asthma confirmed by a chest physician according to international guidelines (GINA 2014); methacholine airway hyperresponsiveness (provocative concentration of methacholine causing a 20% fall in FEV1(forced expiratory volume at one second )【PD20】),>12% improvement in FEV1 10 min after inhaling 200ug of salbutamol. 4. None of the patients with classic asthma had used inhaled or oral corticosteroids, long-acting β2-agonists, leukotriene antagonists, sodium cromoglycate,or nedocromil sodium, anticholinergic agents, during four weeks prior to entry into the study. The patients with CVA 1. Male or female patients aged ≥ 18 and ≤ 65, who have signed an Informed Consent form prior to initiation of any study-related procedure. 2. The diagnosis of CVA is based on isolated cough lasting for ≥ 8 weeks without wheezing or dyspnea, airway hyperresponsiveness (AHR), and relief of cough with bronchodilators according to recommendations in the Chinese national guidelines on the diagnosis and management of cough. 3. None of the patients with CVA had used inhaled or oral corticosteroids, long-acting β2-agonists, leukotriene antagonists, sodium cromoglycate,or nedocromil sodium, anticholinergic agents, during four weeks prior to entry into the study. The patients with EB 1. Male or female patients aged ≥ 18 and ≤ 65, who have signed an Informed Consent form prior to initiation of any study-related procedure. 2. The diagnosis of EB is based on cough lasting for ≥ 8 weeks according to recommendations in the Chinese national guidelines on the diagnosis and management of cough. 3. None of the patients with EB had used inhaled or oral corticosteroids, long-acting β2-agonists, leukotriene antagonists, sodium cromoglycate,or nedocromil sodium, anticholinergic agents, during four weeks prior to entry into the study. Healthy subjects 1. Male or female patients aged ≥ 18 and ≤ 65, who have signed an Informed Consent form prior to initiation of any study-related procedure. 2. Normal spirometry: baseline FEV1 ≥ 80% of the predicted normal value, FEV1/FVC(forced vital capacity) > LLN (lower limit of normal). 3. Normal airways responsiveness. 4. Healthy subjects have no any disease or negative allergen skin prick test results  Patients with classic asthma, CVA and EB The presence of any of the following will a subject from study enrolment: Current smokers, ex-smokers. Individuals with respiratory infection during the previous one month. Clinical history of chronic obstructive pulmonary disease(COPD), bronchiectasis, pulmonary embolism. Clinical history of haematological, immunologic, renal, neurologic, hepatic, endocrinal or other disease, or any condition that might compromise the results or interpretation of the study. Asthma exacerbation and unstable asthma . Pregnant or lactating women