ABSTRACT
Subjects with allergic asthma who inhale an aeroallergen to which they are sensitive become symptomatic with wheeze, cough, chest tightness, and sputum production. Common aeroallergens that evoke this response include cat skin allergen (Fel d 1) and house dust mite allergens (Der p 1 and Der p 2). When airway allergen challenge is performed under carefully controlled conditions in the clinical research laboratory, pulmonary function tests reveal airway obstruction and worsening of bronchial hyperreactivity to histamine or methacholine. Specifically, asthmatic subjects typically demonstrate two patterns of response to inhaled allergen in this setting. Nearly all subjects develop an early asthmatic response (EAR), i.e., symptoms and bronchoconstriction commencing within minutes of inhalation of allergen inhalation and resolving spontaneously within 1 or 2 hours. In addition, approximately 50–60% of asthmatic subjects also develop a late asthmatic response (LAR), i.e., recurrence of symptoms of wheeze and recurrence of bronchoconstriction 3–12 hours after allergen challenge. Exploring the mechanisms of the airway response to inhaled allergen has helped in the development of current theories about the pathophysiology of asthma, and the allergen challenge model has also helped in the development process for new drugs for asthma.
