Nitric oxide (NO) is an important biological mediator and the exhaled form is mainly produced by the nose and paranasal sinuses. In the upper airways, NO has been suggested to involve in host defense, regulation of nasal airway flow and aerocrine messenger. It is now clear that many chronic sino-nasal diseases, including allergic rhinitis (AR), may alter the output of exhaled NO levels. AR is a chronic inflammatory disease of the nasal mucosa. Thus AR related symptoms, disease process and medication directly affect the NO production. In this review, it is aimed to reflect the importance of NO in the AR in the light of the current literature.