Allergic rhinitis and asthma: the link further unraveled.

Allergic asthma and rhinitis are manifestations of the atopic syndrome. Although the diseases commonly occur together, it is still unclear why some allergic patients develop only asthma and others only rhinitis. The reason for the variety in clinical expression of allergic airway disease is not known. Besides a genetic predisposition, environmental factors contribute to the development of the allergic phenotype. Local and systemic inflammatory processes also seem to be involved, however, their exact contribution to the clinical picture of airway allergy still remains to be elucidated. Although it is clear that the condition of the upper airways has an impact on lower airway physiology, the mechanisms underlying this relation are far from being resolved. To date, most data point towards a systemic link between upper and lower airways, involving bloodstream and bone marrow. In this article, the latest developments with regard to nasobronchial interaction in allergic airway disease will be reviewed. Epidemiologic, experimental and clinical data underline the importance of a global approach in allergic rhinitis and asthma.