What Is the Relationship between Airway Hyperresponsiveness and Atopy?

The nature of the relationship between airway hyperresponsiveness (AHR) and atopy (specific IgE to aeroallergens) is unknown and one of the most important questions about asthma. Is AHR a consequence of airway inflammation caused by allergic or other responses or is it a separately inherited state? It is clear from epidemiological studies that these two abnormalities are linked. However, not all allergic (atopic) people have AHR and not all airway-hyperresponsive people are allergic. Furthermore, there is some suggestion that the risk factors for the two abnormalities are different. In Australian children, there has been little increase in the prevalence of atopy but AHR and symptoms have increased so that more of the atopic group now have asthma (1). The data suggest that over the years between 1982 and 1992 in atopic children, the risk factors for AHR have increased or that protective factors have been lost. There have been almost no other studies of atopic status and AHR in randomly selected populations over a period of time to determine if this is happening elsewhere. This article outlines what is known, what is partially known, and the important questions that need to be answered.