Method: 114 patients with CIU were recruited in the study. For each patient, complete medical history was taken and physical examination was done and a questionnaire regarding the characteristics of the disease and exacerbating factors was completed. Urticaria Activity Score (UAS), which is a clinical tool to assess disease severity based on patient-reported outcomes for symptoms, were calculated for patients. One hundred and eighty seven sex-matched and age-matched healthy volunteers from hospital visitors with no history of urticaria or using vitamin supplements were included in the study as the control group.
Vitamin D metabolic statue was measured in serum as 25 hydroxyvitamin D using enzyme immunoassay method. Values less than 20 ng/ml were considered as vitamin D deficiency and vitamin D insufficiency were defined as values of 25-hydroxyvitamin D of 20 to 30 ng/ml.
Results: Patients with chronic idiopathic urticaria significantly showed lower levels of vitamin D. Patients with CIU and particularly with true CIU significantly showed lower levels of 25 (OH)D in comparison with the control group (p=0.005). Vitamin D deficiency was significantly associated with increased susceptibility to CIU (p=0.001). Individuals with vitamin D deficiency showed a 2.4-fold (95%CI: 1.4-4) risk of having CIU. In addition, vitamin D deficiency significantly increased susceptibility to true CIU (p=0.001, OR=2.7, 95%CI: 1.4-5.1). There was a significant correlation between vitamin D levels and UAS (r=0.2, p=0.042). There was not any significant relationship between IgE levels and vitamin D levels..
Conclusion: This study showed that patients with chronic idiopathic urticaria had reduced levels of vitamin D, while vitamin D deficiency could increase susceptibility to chronic idiopathic urticaria.