Must have been on an approved dose of an H1 antihistamine for CIU such as loratadine 10 mg once a day or equivalent, for at least 7 days prior to the screening visit. Approved agents include loratadine 10 qd, desloratadine 5 mg qd, fexofenadine 180 mg qd, cetirizine 10 mg qd or levocetirizine 5 mg qd as once daily medications at the current FDA-approved dose.