[Asthma and allergic rhinitis as symptoms of the same disease: a paradigm under construction].

OBJECTIVE To describe current ideas about the relation between upper and lower respiratory tract and to review the epidemiological, immunological, and pathological aspects that support the paradigm of united airways disease. SOURCES Literature review using the Medline, MD Consult, HighWire, Medscape and Lilacs databases. We used allergic rhinitis and asthma as keywords, and searched articles published in the past 20 years. SUMMARY OF THE FINDINGS Epidemiological evidence includes prevalence of allergic rhinitis in asthmatic patients and vice-versa, results of cross-sectional studies, bronchial hyperresponsiveness in patients with allergic rhinitis, importance of genetic and environmental factors, and the age of onset of atopic disease. Morphological and physiological aspects show structural differences between the nasal and bronchial mucosa, and the mechanisms that could explain the effect of rhinitis on asthma. Immunological aspects including the participation of bone marrow in the production of inflammatory cells and allergic reactions after allergen challenge are the same in allergic rhinitis and asthma. Finally, the results of the therapy for allergic rhinitis in bronchial hyperresponsiveness and in clinical and functional control of asthma are also reported. CONCLUSIONS Epidemiological evidence and immunological and pathological aspects suggest that there is a relation between allergic rhinitis and asthma. The paradigm of united airways disease suggests the implementation of an integrated therapeutic approach.