Allergic rhinitis: epidemiology and natural history.

Establishing a reliable estimate of the prevalence of allergic rhinitis is difficult; prevalence estimates range from as low as 4% to more than 40%. Epidemiology studies suggest the prevalence of allergic rhinitis in the United States and around the world is increasing. The cause of this increase is unknown; however, contributing factors may include higher concentrations of airborne pollution, rising dust mite populations, less ventilation in homes and offices, dietary factors, and the trend toward more sedentary lifestyles. Allergic rhinitis symptoms typically begin in childhood and adolescence and continue into adulthood. In general, allergic rhinitis symptoms slowly improve and skin-test reactivity tends to wane with increasing age. There is a significant trend for symptom improvement with younger age of onset of allergic rhinitis. As the complicated etiology of allergic rhinitis becomes better understood, it may be possible to reverse the trend for increased prevalence.