The Relationship between Allergic Rhinitis and Asthma: One-Airway Disease

Rha, Yeong Ho; Choi, Sun Hee

Abstract

Allergic rhinitis (AR) and asthma are common throughout the world, with a high burden of morbidity and cost. Research and clinical experience over the years has demonstrated that AR and asthma are linked and may therefore be manifestations of the same airway disease, rather than two distinct diseases of the nose and the lung. Similarly, some studies have demonstrated that treatment of either condition in comorbid disease may result in improvement of the other. Epidemiological study suggests that asthma and allergic rhinitis frequently occur as co-morbid conditions in the same patients, with about 80-90% of asthma patients having rhinitis symptoms and about 20-50% of patients with allergic rhinitis having asthma. Furthermore, rhinitis often precedes the onset of clinical asthma and independently increases the risk for developing asthma by up to 3-fold. Allergen provocation indicates that inflammation of the nasal and bronchial mucosa is important, because it is triggered by factors common to both mucosae and plays a pivotal role in the pathogenesis of both AR and asthma. The nasal and bronchial mucosa present similarities, and most patients with asthma also have rhinitis, suggesting the concept of "one airway disease." Although several mechanisms have been proposed to explain the pathophysiological link between the upper and the lower airways, the precise mechanisms underlying the link between AR and asthma are not clearly understood. The patterns of inflammation, when stable or in response to experimental allergen challenge, are similar in the upper and lower airways. Moreover, both asthma and AR may be associated with evidence of systemic inflammation. The progresses achieved in the cellular and molecular biology of airways diseases has documented that inflammation has a important role in the pathogenesis of asthma and rhinitis. The same inflammatory cells seem to be present in the nasal and bronchial mucosa. These findings highlight the potential for improving asthma outcomes by following a combined therapeutic approach to comorbid allergic rhinitis and asthma rather than targeting each condition separately.