The association was affected by: (i) study design, with a stronger correlation between 25(OH)D and serum IgE in the cohort study and cross-sectional studies, than in the case-control study (Fig. 5A) and (ii) baseline vitamin D levels, with a stronger association in studies with mean baseline 25(OH)D ≥ 50 nmol/L or unknown, than in those with vitamin D insufficiency (Fig. 5B). Here, IGHE is linked to vitamin D deficiency.