ABSTRACT
In contrast to what has been observed in infants and preschool children, BHR is strongly associated with asthma and active wheezing in school-age children. In clinical studies, the presence and degree of BHR correlated well with prevalence of physician diagnosis and severity of the disease. Bronchial hyperresponsiveness has been defined as an increased responsiveness of airways to react with an obstruction to a variety of nonspecific factors such as viral infections, pharmacological agents, and physical stimuli. The underlying mechanisms are still not fully understood. Mter allergen exposure, an acute airway obstruction occurs within 15 min in almost all atopic asthmatics (69). In a significant proportion of these subjects-i.e., 70 to 90% of sensitized children with an early response ( 110,111 }-allergen inhalation initiates not only an immediate reaction but also the reappearance of airway obstruction 3 to 8 hr later: the late asthmatic reaction. This dual response is characterized by features typical of chronic asthma, such as decreased responsiveness to bronchodilator therapy, increased BHR, and the development of bronchial inflammation (112,113).
