Vitamin D deficiency is associated with diagnosis and severity of childhood atopic dermatitis

Background Recent studies implicated the importance of vitamin D in innate immune defense and pathogenesis of allergic diseases. However, the impact of vitamin D deficiency on atopic dermatitis ( AD ) diagnosis and severity remains unclear. This case–control study investigated such relationship in H ong K ong C hinese children. Methods Serum 25‐hydroxyvitamin D [25( OH )D] levels of 498 AD children and 328 non‐allergic controls were measured by immunoassay. Subjects were categorized into deficient (<25 n m ), insufficient (25–49.9 n m ), and sufficient (≥50 n m ) groups. Short‐term and long‐term AD severity was evaluated by physician‐diagnosed SCOR ing A topic D ermatitis ( SCORAD ) and N ottingham E czema S everity S core ( NESS ), respectively. Atopy biomarkers were also measured for analysis. Results The mean (s.d.) serum 25( OH ) D levels in AD patients and controls were 28.9 (15.3) and 34.2 (14.5) n m, respectively (p <   0.001). More patients had serum 25( OH )D levels <25 n m than controls (47.8% vs. 26.6%). AD severity as indicated by both SCORAD and NESS showed inverse associations with serum 25( OH )D levels (respective p =   3.6 × 10 −4 and 0.004 when adjusted for age, sex, month of assessment, and immunoassay batch as covariates). Vitamin D ‐deficient patients (3.08 ± 0.76) had higher logarithm‐transformed total IgE than those with insufficient (2.74 ± 0.69) and sufficient (2.72 ± 0.72) serum 25( OH ) D levels (p <   0.001). The proportion of subjects with elevated I g E was higher in vitamin D ‐deficient (43.2%) than vitamin D ‐sufficient (20.0%) groups. Conclusions Vitamin D deficiency and insufficiency are prevalent in H ong K ong C hinese children. Vitamin D deficiency is associated with childhood AD and high total I g E . Serum 25( OH ) D levels correlate inversely with both long‐ and short‐term AD severity.