The role of allergy in the development of asthma

Recent studies have shown that initial sensitization to airborne environmen tal allergens occurs typically in early childhood, but subsequent progressi on to persistent atopic asthma, which may not manifest for several years, i s restricted to only a subset of atopics. The key to establishing the link between atopy and asthma lies in the development of persistent inflammation in the airway wall, resulting in structural and functional changes in loca l tissues which are responsible for the symptoms of the disease. This revie w summarizes recent findings on the nature of the cellular and molecular me chanisms underlying this process, and addresses the issue of why the intens ity and duration of these tissue-damaging responses in the airway wall appa rently exceeds the critical threshold required for development of persisten t asthma in only a minority of allergy sufferers.