The purpose of this study is to compare urticaria lesions (size, kinetics) by thermography, volumetry and digital time lapse photography in CU patients treated with desloratadine 5 mg or desloratadine 20 mg. Hypothesis: Updosing of desloratadine (20mg) is more efficient in the treatment of urticarial lesions as compared to standard dosing (5 mg desloratadine).