Canadian Health&Care; Mall

Patients Thirty-five subjects were studied, of whom 12 were nonatopic, healthy subjects, 10 were atopic nonasthmatics and 13 were atopic asthmatics. All patients gave signed consent before the study. The study was approved by the Ethics Committee of the McMaster University Health Sciences Centre, Hamilton, Ontario. The asthmatic group consisted of nine male and four female patients with a median age of 35 years (range 22 to 50 years). All of the patients had mild asthma as detailed by the American Thoracic Society criteria and had airway hyperresponsiveness to inhaled methacholine, with a geometric mean provocation concentration of methacholine causing a fall in forced expiratory volume in 1 s of 20% of 3.70 mg/mL (geometric standard error of the mean 1.43 mg/mL). No subject was treated with regular asthma therapy, and all subjects used only an inhaled beta2-agonist as needed, less than daily. Medication was withheld for at least 8 h before the investigation. The atopic nonasthmatic group consisted of eight male and two female subjects (median age 36 years, range 28 to 43 years) who had a history of allergic rhinitis and/or conjunctivitis but who had never had asthmatic symptoms. Atopy was identified by positive skin prick test responses to one or more of the following allergens: house dust mite, mixed grass pollens, mixed tree pollens, mixed feathers, cat fur and dog hair. They did not take any medications. No asthmatic or atopic nonasthmatic subject suffered from any comorbid condition.