ABSTRACT
Asthma is a disease that continues to defy specific definition and for which there is no specific diagnostic test. In spite of uncertainty as to specifics, scientific experimentation and careful observation have improved our knowledge of the disease. Asthma is now understood to be an inflammatory disorder of unknown cause. Three distinct components are recognized: the asthma exacerbation (i.e., an episode of airway obstruction that resolves spontaneously or as a result of treatment); hyperresponsiveness of the airways to a variety of provocative stimuli; and persistent "inflammation" of the airways. There is good reason to believe that the airway inflammation of asthma is linked to the biology of airway obstruction and hyperresponsiveness, but the nature of these links remains elusive.
