['Acute urticaria is an immune-inflammatory disease, characterised by acute immune activation. There has been increasing evidence showing that vitamin D deficiency is associated with increased incidence and severity of immune-inflammatory disorders.', 'The aim of this study was to evaluate serum vitamin D levels in acute urticaria.', 'We enrolled 30 children with acute urticaria and 30 control subjects. Concentrations of 25-hydroxyvitamin D [25(OH)D], a biomarker of vitamin D status, were measured in serum of acute urticaria patients and compared with the control group.', 'There were no significant differences in baseline variables (age, gender, weight) between the groups. Vitamin D deficiency (<20ng/ml) was significantly higher in patients with acute urticaria than in control patients. Serum 25(OH)D levels were significantly lower in the study group compared to those in the control group (13.1±4.3 vs 28.2±7.4ng/mL, p<0.05). Moreover, we found negative correlation between mean duration of acute urticaria and serum vitamin D levels (p<0.01).'] Do serum vitamin D levels decrease in children with acute urticaria?