Target Population

Individuals with stable, mild, allergic asthma and using only intermittent shortacting bronchodilators for the treatment of their asthma are suitable subjects for inhaled allergen challenges. Those requiring regular medications for the treatment of their asthma are not an appropriate population to test, because most classes of asthma drugs interfere with the allergen-induced responses.

Safety Considerations

Allergen challenges are conducted safely in laboratories with highly trained and experienced staff. Results from skin tests and airway responsiveness to

Percent change in forced expiratory volume in 1 s

FIGURE 10.7 Percent change in forced expiratory volume in 1 s (FEVj) after allergen inhalation challenge in subjects with mild allergic asthma with placebo treatment (lower curve) and following treatment with an effective antiasthma therapy (upper hatched curve). The magnitude of the early asthmatic response occurring acutely postchallenge and the late asthmatic response beginning at 3 h postchallenge are compared between active treatment and placebo control.

methacholine/histamine can be used to accurately predict the allergen PC20 (Cockcroft et al. 2005), and a stepwise approach to administering allergens will prevent overdose. Administering allergen can lead to loss of asthma control in those with more severe disease; thus, these challenges are not recommended for patients with moderate-to-severe asthma.

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