Levocetirizine Effect on Nasal Nitric Oxide and Nasal Eosinophils in Subjects With Perennial Allergic Rhinitis

Inclusion Criteria: * ICF signed * Diagnosis of PAR for 6-12 months greater * 12 years and older * Decreased nasal NO values at baseline * Compliance and ability to perform maneuvers and responsibilities Exclusion Criteria: * Oral or systemic steroids for 60 days prior * Inhaled, nasal, nebulized steroids w/i 4 weeks * Hospitalization or life threatening asthma * Use of nasal or oral antihistamines w/i 4 weeks * Upper or lower airways infection * Direct cigarette smoke exposure