Experimental protocols. a. Vitamin D evaluation and treatment regimen of Chronic Urticaria patients. Patients were stratified into 4 groups depending upon VitD levels. Group 1, 2, 3 and 4 consisted of patients with serum 25(OH)2D levels <10ng/ml, ≥ 10 ng/ml to < 20 ng/ml, ≥ 20 to 30 ng/ml and >30ng/ml respectively. All the groups were further randomized into 3 treatment protocol regimens, a, b and c. 48 Patients in Protocol a received Vitamin D (VD) for 4 weeks, 42 patients in group b received antihistamines and corticosteroids (H+S) for 6 weeks and 57 patients in group c received a combinatorial therapy of vitamin (4 weeks) + antihistamines+ corticosteroids (VD+H+S) for 6 weeks. 130 healthy controls (HC) in group d were followed as such without any intervention. Patients were tested for Vit D, VAS and 5D score at the baseline and after 6 weeks of treatment. b. Outline of experiment starting from recruitment to attaining the end point. Participants were screened for eligibility starting 4 weeks before the start of the experiment (Screening). The patients that do not fill the eligibility criteria and/or developed secondary disorders during the treatment were excluded from this study (E₭). Follow up visit for safety assessment was at 2,4,6,8 and 10 weeks after the start of the study (F₴). The treatment lasted for 6 weeks with follow up and safety assessment for another 4 weeks. The sample size calculations was chosen in a way that the test for the primary end point, the mean weekly VAS and 5-D score, would have 85% power by using a 2-sided 5% significance level of the treatment effect (i.e., the difference between the treatment groups) was at least as large as its SD (standardized effect size, >1).