This was a randomized, double-blind, parallel-group, multicenter study that used both an active control (cetirizine) and a placebo control to evaluate desloratadine 5 mg once daily during a 28-day treatment period. The active treatments and placebo were allocated in a 2:2:1 ratio.

Inclusion Criteria:

• Have demonstrated their willingness to participate in the study and comply with its procedures by signing a written informed consent. For pediatric patients, the parent or legal guardian was to have signed a written informed consent.
• Be between 12 and 70 years of age, of either sex and any race.
• Had signs and symptoms of CIU for at least 6 weeks prior to the Screening Visit.
• Have been experiencing a current flare of their CIU of at least 3 weeks prior to the Baseline Visit. Hives were to have been present for at least 3 days per week during the current flare prior to the Baseline Visit.
• Have an overall condition of CIU that was at least of "moderate" severity (minimum score of 2) at both Screening and Baseline Visits.
• Have at least a moderately severe pruritus score (minimum score of 2) and hives (minimum score of 1) present at Screening.
• Have, at Baseline, a total pruritus score of >= 14 for the sum of AM and PM (reflective) diary scores for the 3 days prior to Baseline and the AM diary score on Day 1.
• Understand and be able to adhere to the dosing and visit schedules, and agree to assess and record their symptom severity scores, medication times, concomitant medications, and adverse events accurately and consistently in a daily diary.
• Be in general good health and free of any clinically significant disease (other than CIU) that would have interfered with study evaluations.
• If female and of childbearing potential, have had a negative urine (hCG) pregnancy test at the time of Baseline (Visit 2).
• Female subjects of childbearing potential were to be counseled in the appropriate use of birth control while in the study. They were to be using a medically accepted method of birth control

Exclusion Criteria:

• Had asthma requiring chronic use of inhaled or systemic corticosteroids.
• Had been unresponsive to antihistamine treatment in the past.
• Had a history of allergies to more than two classes of medication or who were allergic to or unable to tolerate antihistamines.
• Had used any investigational drug in the last 30 days prior to Baseline.
• Had food or drug allergies manifested as skin reactions. Subjects with urticaria that was primarily due to physical urticaria or other known etiology.
• If female, were pregnant or nursing.
• Had a history of hypersensitivity to the study drug or its excipients.
• Were family members of the investigational study staff involved with this study.
• Had previously been randomized into the study.
• Had current evidence of clinically significant hematopoietic, cardiovascular, hepatic, renal, neurologic, psychiatric, autoimmune disease, or other disease that precluded the subject's participation in the study. Particular attention was to be given to subjects with conditions that would interfere with the absorption, distribution, metabolism, or excretion of the study medication or with the subject's ability to reliably complete the diary card.
• Were morbidly obese (BMI >= 35, as described in Appendix 6 of the protocol)
• Had a compromised ability to provide informed consent.
• Had a history of non-compliance with medications or treatment protocols.