This was a crossover study designed to see if patients with allergy symptoms preferred Clarinex® or Zyrtec®. Patients were randomized to take 7 days of Clarinex or Zyrtec treatment, followed by a 5 to 28-day washout period (days when no drug is given), followed by 7 days of the opposite treatment. At the end of each 7-day treatment, patients were asked questions to determine which drug, Clarinex or Zyrtec, the patient prefers more.

Inclusion Criteria:

• had at least a two-year history of seasonal allergic rhinitis and/or perennial allergic rhinitis;
• currently experiencing symptoms of AR, including nasal symptoms at Visits 2 and 4, prior to entering each treatment phase;
• had not taken Zyrtec® or Clarinex® within the previous year;
• were 18 years of age or older;
• had negative urine test (hCG) for females of childbearing potential;
• for women of childbearing potential, agreed to use a medically accepted method of birth control;
• were free of any clinically significant disease (other than AR) that would interfere with study evaluations.

Exclusion Criteria:

• were pregnant or nursing;
• had allergic or idiosyncratic reaction to antihistamines;
• had current or history of frequent, clinically significant sinusitis or chronic purulent nasal discharge;
• had rhinitis medicamentosa or nasal structural abnormalities (including large nasal polyps and marked septal deviation) that significantly interfered with nasal airflow;
• in the opinion of the Investigator, were dependent upon nasal, oral or ocular decongestants, nasal topical antihistamines, or nasal steroids (ie, subjects who could or would not observe the washout period for these prohibited medications);
• had an upper respiratory tract or sinus infection that required antibiotic therapy with the last dose within 14 days prior to Screening, or had a viral upper respiratory infection within 7 days prior to Screening;
• had asthma, unless their symptoms could be controlled by a short-acting inhaled Beta2-agonist used on an "as needed" basis;
• were on immunotherapy, unless they were on a stable maintenance schedule prior to screening. The dose of immunotherapy should remain constant and subjects could not receive immunotherapy within 24 hours prior to any visit;
• had a history of psychosis, antagonistic personality, poor motivation, hypochondriasis, or any other emotional or intellectual problems that were likely to limit the validity of consent to participate in the study;
• had a history of non-compliance with medications or treatment protocols;
• had any clinically significant deviation from normal in the physical examination that, in the Investigator's judgment, may have interfered with the study evaluations or affect subject safety;
• had any clinically significant metabolic, cardiovascular, immunologic, neurologic, hematologic, gastrointestinal, cerebrovascular, or respiratory disease, or any other disorder which, in the judgment of the Investigator, might interfere with the study evaluations or affect subject safety;
• had liver or renal impairment.