Upper and lower respiratory diseases, including asthma, sinusitis, and otitis media with effusion, frequently complicate allergic rhinitis. The close association of nasal allergies with these conditions has been supported by extensive epidemiologic evidence. Similar models have been proposed to explain the pathophysiologic links between allergic rhinitis and both sinusitis and otitis media with effusion. In these models, inflammation caused by nasal allergy and/or viral infection leads to obstruction, fluid accumulation, bacterial infection, and acute disease. If these diseases are unsuccessfully treated, a chronic state of inflammation, obstruction, and infection develops that can cause mucosal damage and, ultimately, chronic disease. A number of studies have investigated the roles and interactions of viruses and allergens in the development of otitis media with effusion. Diagnosing and prophylactically treating nasal allergies in patients with this condition may help prevent recurrent episodes and improve the response to therapy.