Background: Allergic disorders are characterized by type 2 helper T cell (Th2)-polarization, thus physiological type 1 helper T cell (Th1)-dependent mechanisms involved in fighting respiratory infections (RI) may be defective. It has previously been reported that allergic children have more numerous and severe RI than nonallergic ones.
Objective: The aim of the study was to evaluate the number and duration of RI in adult allergic and nonallergic subjects.
Methods: Six hundred and twenty-four subjects were studied; 202 of them were allergic (i.e. suffering from allergic rhinitis). The number of RI as well as the duration of the disease were recorded for 2 years.
Results: Allergic subjects showed a significantly higher rate of RI episodes [adjusted incidence rate ratio (IRR) = 2.16, 95% confidence interval (CI) 1.94–2.41, P < 0.001] than subjects without allergy. The number of mild RI episodes was slightly higher in allergic subjects (IRR = 1.68, 95% CI 1.50–1.89, P < 0.001), while the number of severe episodes was markedly higher (IRR = 15.71, 95% CI 10.35–23.84, P < 0.001) when compared with nonallergic subjects. Moreover, allergic patients showed a longer total duration of RI than nonallergic subjects, with a mean difference of 17.4 days (95% CI 15.5–19.4, P < 0.001).
Conclusions: This study provides evidence that adult allergic patients have more numerous and prolonged RI than nonallergic subjects.