A common pathway: asthma and allergic rhinitis.

Historically, the structural and functional differences within the respiratory tract have been the basis for separating the airway into upper and lower entities. For centuries, researchers suggested similar mechanisms in asthma and rhinitis. The implications of such a connection are significant in that asthma and allergic rhinitis (AR) are associated with a high prevalence in adults and children, substantial health care costs, and, often, serious negative effects on quality of life. The importance of the unified airway hypothesis lies in the rational approach to treatment. Management approaches that consider the association between asthma and AR may improve overall outcomes in patients with both diseases. Because the treatment of AR may affect concomitant asthma, significant improvements in health status may occur in some patients. The following review discusses the epidemiology of asthma and AR, provides evidence for common pathophysiological mechanisms, and discusses a therapeutic approach that has positive effects on both diseases, and thereby may maximize benefits and outcomes for patients with concomitant asthma and AR.