Correlation of serum 25-Hydroxyvitamin D levels with total IgE and peripheral blood eosinophil counts in patients with atopic dermatitis

Background: This study was conducted to investigate the correlations and independent associations between serum 25-hydroxyvitamin D (25[OH]D) levels and total immunoglobulin E (IgE) values as well as peripheral blood eosinophil (EOS) counts in adults with atopic dermatitis (AD). Methods: This single-center cross-sectional study included 148 adults with AD. Data on age, sex, body mass index, disease duration, season, sensitization status, and allergic comorbidities were collected. Serum 25(OH)D values, total IgE levels, and EOS counts were measured, and the Dermatology Life Quality Index (DLQI), Eczema Area and Severity Index (EASI), and SCORing Atopic Dermatitis (SCORAD) scores were assessed. EOS counts and total IgE levels were designated as coprimary end points, and Bonferroni-adjusted p-values were calculated to control for multiple testing. Results: The median serum 25(OH)D level was 19 ng/mL, and vitamin D deficiency or insufficiency was common. Serum 25(OH)D was inversely correlated with EOS counts (r = −0.502, raw p < 0.001; p < 0.002, Bonferroni adjusted) and total IgE levels (r = −0.492, raw p < 0.001; p < 0.002, Bonferroni-adjusted). Both associations remained statistically significant in the fully adjusted regression models after Bonferroni adjustment. Higher vitamin D categories showed decreasing trends in EOS counts and total IgE levels (both raw p-values for trend < 0.001; both Bonferroni-adjusted p-values for trend < 0.002). However, no statistically significant differences in EASI and SCORAD scores were detected among vitamin D categories (p = 0.160 and p = 0.080, respectively). Conclusion: In adults with AD, serum 25(OH)D was inversely associated with peripheral blood EOS counts and total IgE levels, whereas no statistically significant differences in the clinical severity scores were detected across vitamin D categories. Analysis of these findings suggests an association with systemic inflammatory markers rather than established clinical utility.