Asthma affects millions of people worldwide, and its reported incidence is increasing dramatically in many developed nations; the human and economic costs of this disorder, in morbidity, health care expenses, lost productivity, and, most tragically, even mortality, are staggering (1, 2).
It is now generally thought that asthma is a syndrome, typically characterized by the three cardinal features of intermittent and reversible airway obstruction, airway hyperresponsiveness, and airway inflammation, that may arise as a result of interactions between multiple genetic and environmental factors (1–4). Nevertheless, most cases of the disorder (the so-called “atopic” or “allergic” asthma) occur in subjects whom also exhibit immediate hypersensitivity responses to defined environmental allergens, and challenge of the airways of these subjects with such allergens can produce reversible airway obstruction (1–5). It is also known that the overall incidence of asthma in several...
