Patient description: A 63-year-old man presents with cough and shortness of breath. His past medical history is notable for heavy smoking, spinal stenosis, diabetes, hypothyroidism and mild psoriasis. He also has a family history of early onset dementia. His symptoms began about a week prior to his admission, with productive cough, purulent sputum and difficulty breathing, requiring him to use his home oxygen for the past 24 hours. He denies fever. On examination he is cyanotic, tachypneic, with a barrel shaped chest and diffuse rales over his lungs. A chest x-ray is notable for hyperinflation with no consolidation.

Clinical trial eligibility criteria: eligible ages (years): 18.0-50.0,  Rhinitis, Allergic, Perennial Rhinitis, Allergic, Seasonal Asthma Specific allergy to at least one of the following allergen preparations: (House Dust Mite f, House dust mite p, Cockroach, Tree mix, Grass Mix, Weed Mix, Mold Mix 1, Mold Mix 2, Rat, Mouse, Guinea Pig, Rabbit, Cat or Dog) confirmed by positive immediate skin test response FEV1 of at least 80% of predicted and FEV1/FVC ratio of at least .75 (without use of bronchodilating medications for 12 hours), consistent with lung function of persons with no more than mild episodic or mild persistent asthma History of nasal allergy, including episodic, perennial, or seasonal sneezing, nasal congestion or cough, or such symptoms associated with specific exposures (such as cat or dog) for classification as having asthma with allergic rhinitis vs. allergic rhinitis alone History of episodic wheezing, chest tightness, or shortness of breath consistent with asthma, or physician diagnosed asthma Provocative concentration of methacholine producing a 20% fall in FEV1 (PC20 methacholine) of less than 10 mg/ml by the method used (see below)  Any chronic medical condition considered by the PI as a contraindication to the exposure study including significant cardiovascular disease, diabetes requiring medication, chronic renal disease, or chronic thyroid disease Physician directed emergency treatment for an asthma exacerbation within the preceding 12 months Use of systemic steroid therapy within the preceding 12 months for an asthma exacerbation. All use of systemic steroids in the last year will be reviewed by a study physician Use of inhaled steroids, cromolyn or leukotriene inhibitors (Montelukast or zafirkulast) initiated within the past month (except for use of cromolyn exclusively prior to exercise). Patients must be on a stable regimen of therapy and shown to be stable Use of daily theophylline within the past month Pregnancy or nursing a baby Cigarette smoking > 1 pack per month Nighttime symptoms of cough or wheeze greater than 1x/week at baseline (not during a clearly recognized viral induced asthma exacerbation) which would be characteristic of a person of moderate or severe persistent asthma as outlined in the current NHLBI guidelines for diagnosis and management of asthma Exacerbation of asthma more than 2x/week which would be characteristic of a person of moderate or severe persistent asthma as outlined in the current NHLBI guidelines for diagnosis and management of asthma Daily requirement for albuterol due to asthma symptoms (cough, wheeze, chest tightness) which would be characteristic of a person of moderate or severe persistent asthma as outlined in the current NHLBI guidelines for diagnosis and management of asthma. (Not to prophylactic use of albuterol prior to exercise)