The asthma and allergic rhinitis link.

During the past 10 years, our understanding of asthma and allergic rhinitis (AR) has evolved. The historic perspective of these allergen-induced disorders as distinct and separate entities is being displaced by current thinking that they are described better as a continuum of inflammation involving one common airway. Therefore, traditional therapies originally indicated for AR and asthma are being reassessed to explore their potential value in both upper- and lower-airway diseases. Recently, there has been a renewed interest in the role that histamines play in lower-airway disease, and interest is increasing in the leukotrienes (LTs), which are far more potent inflammatory mediators than histamines, and the role they play in upper-airway disease. Given the pivotal role that LTs play as potent inflammatory mediators in the pathophysiological state of inflammation of both airways, LT receptor antagonists recently have emerged as important therapeutic advances that have potential clinical value in both asthma and allergic rhinitis. The prevalence of asthma and AR is increasing in the general population, and a high proportion of new patients have coexisting upper- and lower-airway disease. Estimates show that 60-78% of patients who have asthma have coexisting AR. 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 may maximize benefits and outcomes for patients with concomitant asthma and AR.