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): 18.0-45.0,  Asthma Allergic Asthma for all subjects Age between 18 and 45 years old Smoking history ≤2 packyears. Specific for the two groups Group 1. Patients with ongoing asthma Age of onset of asthmatic symptoms: 0 years Documented history of asthma diagnosed according to latest GINA guidelines, i.e. respiratory symptoms and either bronchodilator reversibility (improvement in FEV1 of more than 12% of baseline (and at least 200 mL) after inhalation of 800 µg salbutamol) Use of inhaled corticosteroids or either persistent symptoms of wheeze, cough, or dyspnea or regular use of β2 agonists at least once a week during the last 2 months PC20 methacholine < 8 mg/ml Group 2. Non-asthmatic controls  FEV1 <1.2 L Subjects must be able to adhere to the study visit schedule and other protocol requirements A subject is not eligible to enter and participate if he has not signed and dated a written informed consent form prior to participation in the study A subjects is not eligible to enter and participate if he does not agree that we inform his general practitioner Upper respiratory tract infection (e.g. colds), within 6 weeks Serious acute infections (such as hepatitis, pneumonia or pyelonephritis) in the previous 3 months Signs or symptoms of severe, progressive or uncontrolled renal, hepatic, hematologic, endocrine, pulmonary, cardiac, neurologic or cerebral disease Malignancy within the past 5 years (except for squamous or basal cell carcinoma of the skin that has been treated with no evidence of recurrence) Known recent substance abuse (drug or alcohol) Females of childbearing potential without an efficient contraception unless they meet the following definition of post-menopausal: 12 months of natural (spontaneous) amenorrhea or 6 months of spontaneous amenorrhea with serum FSH >40 mIU/mL or the use of one or more of the following acceptable methods of contraception: 1. Surgical sterilization (e.g. bilateral tubal ligation, hysterectomy). 2. Hormonal contraception (implantable, patch, oral, injectable). 3. Barrier methods of contraception: condom or occlusive cap (diaphragm or cervical/vault caps) with spermicidal foam/gel/cream/suppository. 4. Continuous abstinence