The Effect of Desloratadine and Levocetirizine on Nasal Obstruction (Study P03609)

Inclusion Criteria: * 18 to 45 years of age * Were free of any clinically significant disease that would interfere with study evaluations. * Demonstrated hypersensitivity to the grass allergen used in the chamber unless confirmed previously within 12 months. * Hypersensitivity to the allergen was documented by a positive response to the skin prick test with a wheal diameter at least 3 mm larger than the diluent control and by a radioallergosorbent test (RAST) class of \>=2 (rating scale 0 -6). * Had a history of SAR for at least 2 years, as diagnosed by the investigator, another physician, or subject-provided history. * Reported having shown therapeutic efficacy with previous use of an antihistamine (without a decongestant). * At the screening allergen provocation, the subject had a nasal obstruction symptom severity score of at least moderate (\>=2) and a decrease from baseline in nasal airflow (mL/sec) measured by rhinomanometry of \>=30% within 2 hours of allergen exposure. Also, the subject had a nasal obstruction symptom severity score of none or mild (\<=1) prior to exposure to allergen. Exclusion Criteria: * Women who were pregnant or nursing. * Had a body mass index (BMI) \>=30 kg/m\^2. * Had asthma; were being treated with inhaled or oral corticosteroids, chromones, theophylline, leukotriene inhibitors, or short-acting inhaled β2-agonists (except during or immediately after the allergen exposures); and could not go through the washout periods and the entire study without needing these medications. * Developed wheezing or dyspnea during the screening allergen exposure. * Had a respiratory infection during the 4 weeks prior to pre-dose evaluations. * Had any clinically significant deviation from normal in the physical examination that, in the investigator's judgment, could interfere with the study evaluation or affect subject safety. * Had any history of or laboratory evidence of hepatic failure or renal failure with a glomerular filtration rate (GFR) known to be \<30 mL/min. * Had a known potential for hypersensitivity, allergic, or idiosyncratic reaction to the study drug or excipients. * Had nasal structural abnormalities, including large nasal polyps and marked septum deviation, that significantly interfered with nasal airflow.