Background: the link between allergic rhinitis (AR) and asthma has been confirmed. AR is a risk factor for the onset of asthma. Spirometry is a noninvasive method to evaluate the lower respiratory system function in AR patients. The aim of the study: to evaluate spirometric lung functions and response to the post-bronchodilatation test in patients with allergic rhinitis.………………………………………... Patients and Methods:This prospective cross-sectional study carried out on 100 patients with persistent AR. Spirometry, post-bronchodilatation test, serum total IgE and estimation of eosinophils in blood and sputum were performed for all patients.…………………………………… Results: Our results reconfirming the concept of "a single airway with a single disease". In our study, patients with persistent AR had impaired spirometric parameters. Conclusion: Our study confirming the predictive value of forced expiratory flow at 25% and 75% (FEF 25-75) as a marker of early bronchial involvement of small airway disease (SAD) in AR and also confirm the link between upper and lower respiratory system.