Direct infant ultraviolet light exposure is associated with eczema and immune development: a critical appraisal.

Abstract

Rueter etal. aimed to 'determine the effects of early postnatal vitamin D supplementation on infant eczema and immune development'. This was a double-blind randomized placebo-controlled trial with an additional nonrandomized exploratory analysis on the effects of ultraviolet (UV) exposure led from a hospital setting. Vitamin D (400 iU daily) drops or placebo drops (coconut and palm kernel oil) were allocated randomly to 195 infants born to families with a first-degree relative with atopic disease. Eighty-six of these infants were allocated personal UV dosimeters in a nonrandomized fashion to measure UV light (290-380 nm) exposure until 3 months of age. Eczema and wheeze were assessed at 3 and 6 months, and 25 immune function markers were assessed at 6 months of age. Infant vitamin D levels and immune functions were measured at 6 months of age. Although vitamin D levels were significantly greater in infants in the intervention group than in those in the placebo group at 3 and 6 months of age, there was no difference in eczema between groups at either time point (10·0% vs. 6·7% at 3 months and 21·8 vs. 19·3% at 6 months for the vitamin D and placebo groups, respectively). In the subset of infants given a dosimeter, those with eczema had less UV light exposure (median 555 J m-2 ) than infants who did not develop eczema (median 998 J m-2 ). Across the 25 immune functions, UV light exposure was inversely correlated with interleukin-2, granulocyte macrophage colony-stimulating factor and eotaxin production by Toll-like receptor ligands. Vitamin D supplementation in high-risk infants increased vitamin D levels but did not reduce eczema. Exploratory post-hoc analyses in a nonrandomized subset showed an association between greater direct UV light exposure and reduction of eczema. The authors claim that their 'findings indicate that UV light exposure appears more beneficial than vitamin D supplementation as an allergy prevention strategy in early life'.