Vitamin D supplementation does not reduce the risk for asthma exacerbation in children overall but does reduce the risk in those with low serum 25-hydroxyvitamin D (25[OH]D) concentrations, according to a study published in Nutrients. Researchers conducted a systematic review and meta-analysis to examine the effects of vitamin D supplementation in children with allergic diseases. Data were included from 32 randomized controlled trials (RCTs) comparing vitamin D supplementation with placebo among 2,347 children. Compared with placebo, vitamin D supplementation did not reduce the risk for asthma exacerbations overall (risk ratio [RR], 0.84; 95% CI, 0.65-1.08; P=0.18), but a reduction was observed in the risk for asthma exacerbation for children with baseline serum 25(OH)D less than 10 ng/mL (RR, 0.48; 95% CI, 0.28-0.83; P=0.009). A significant reduction was seen in the Scoring Atopic Dermatitis or the Eczema Area and Severity Index scores in children with atopic dermatitis with vitamin D versus placebo (standardized mean difference, −0.5; 95% CI, −0.87 to −0.12; P=0.009).