Patient description: A 4 year old boy presents to the emergency room with wheezing. He has had a history of allergic rhinitis, but no history of wheezing. His mother reports that 5 hours ago patient was playing in the backyard sandbox when she heard him suddenly start coughing. The coughing lasted only moments, but he has been audibly wheezing since. Mother was concerned, because his breathing has not returned to normal, so she brought him to the ED. On exam, the child is playful and well appearing. Wheezing is heard in the mid-right chest area. O2 sats are 100% on room air.

Clinical trial eligibility criteria: eligible ages (years): 18.0-50.0,  Mild, Allergic Asthma Age 18-50 of both genders Negative pregnancy test for females who are not s/p hysterectomy with oopherectomy History of episodic wheezing, chest tightness, or shortness of breath consistent with asthma, or physician diagnosed asthma Positive methacholine test. A positive test is defined as a provocative concentration of methacholine of 10 mg/ml or less producing a 20% fall in FEV1 (PC20 methacholine) by the method used in a separate screening protocol FEV1 of at least 80% of predicted and FEV1/FVC ratio of at least .70 (without use of bronchodilating medications for 12 hours or long acting beta agonists for 24 hours), consistent with lung function of persons with no more than mild episodic or mild persistent asthma Allergic sensitization 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 Symptom Score (this will be submitted as an attachment) no greater than 16 (out of a possible 24) for total symptom score with a value no greater than 3 for any one score. No more than one score may be greater or equal than 3 subjects must be willing to avoid caffeine for 12 hours prior to all visits  Any chronic medical condition considered by the PI as a contraindication to the exposure study including significant cardiovascular disease, diabetes, chronic renal disease, chronic thyroid disease, history of chronic infections/immunodeficiency, history of tuberculosis Physician directed emergency treatment for an asthma exacerbation within the preceding 12 months Moderate or Severe 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) Viral upper respiratory tract infection within 2 weeks of challenge Any acute infection requiring antibiotics within 2 weeks of exposure or fever of unknown origin within 2 weeks of challenge Severe asthma Mental illness or history of drug or alcohol abuse that, in the opinion of the investigator, would interfere with the participant's ability to comply with study requirements Medications which may impact the results of the CCRE exposure, interfere with any other medications potentially used in the study (to steroids, beta antagonists, non-steroidal anti-inflammatory agents)