Efficacy of Levocetirizine and Cetirizine in Reducing Symptoms of Seasonal Allergic Rhinitis in Ragweed Sensitive Subjects

Inclusion Criteria: * Male/Female, aged \>= 16 years * seasonal allergic rhinitis that required pharmacologic therapy each year during the last 2 ragweed pollen seasons * documented seasonal allergy to ragweed pollen * total symptom score of at least 18 points. Exclusion Criteria: * nasal anatomic deformities ? 50% obstruction * acute sinusitis within 30 days of Period 2 * initiated or advanced an immunotherapy regimen * immunotherapy injections within 48 hours of pollen exposure * impaired hepatic function * history of malignancy * intolerance to histamines * asthma requiring medication more than occasionally