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): 12.0-69.0,  Asthma Asthmatic participants Males or females greater than or equal to 12 and less than 70 years of age Physician-diagnosed and investigator-confirmed stable asthma (excluding exercise induced asthma) Current treatment for asthma by a healthcare provider within the preceding twelve months: current asthma treatment defined as regular use of asthma medications. Asthma medications short and long acting adrenergic bronchodilators, bronchodilator combinations, inhaled anticholinergics, inhaled corticosteroids, cromolyn sodium and nedocromil, leukotriene modifiers and methylxanthines Stable asthma defined by no asthma exacerbation (emergency room visit, hospitalization, course of increased systemic steroids, or urgent health care visit for asthma) during the prior four weeks Forced expiratory volume at one second (FEV1) >70% predicted pre-bronchodilator Ability to provide screening and baseline information Ability and willingness to provide informed consent For women of childbearing potential: not pregnant, non-lactating, and agree to practice an adequate birth control method (abstinence, combination barrier and spermicide, or hormonal) for the duration of the study  Chronic oral steroid therapy (daily) Oral corticosteroid use within past 4 weeks Respiratory tract infection within past 4 weeks Chronic diseases (other than asthma) that in the opinion of the investigator would prevent participation in the trial or put the participant at risk by participation, e.g. chronic diseases of the lung (other than asthma), heart, liver, kidney, or nervous system, or immunodeficiency Known allergy to methacholine (for example, a previous bad reaction to methacholine) or to any other parasympathomimetic agents Current use of beta adrenergic blocking agent (a heart medicine) or a cholinesterase inhibitor (medicine used to treat myasthenia gravis or Alzheimer's disease) History of epilepsy, cardiovascular disease with bradycardia (slow heart beat), vagotonia (increased activity of the vagus nerve causing slow heart rate or low blood pressure), peptic ulcer disease, thyroid disease, or urinary tract obstruction History of cigarette smoking within the past 5 years or >10 pack years total Use of investigative drugs or intervention trials in the 30 days prior to enrollment or during the duration of the study Any condition or compliance issue which in the opinion of the investigator might interfere with participation Nonasthmatic control