Methods: Of 1,436 parent-infant pairs, 981 (68.3%) infants over the first 6 months of life without vitamin supplement intake were enrolled in this cross-sectional study in 2009. We assessed postnatal infantile sunlight exposure, a parental family history of allergic diseases (FH) and physician-diagnosed AD by self-writing questionnaires. Sunlight exposure was separated into 3 timings; until the first 6 months of life, over the first 6 months of life and now. We performed statistical analyses by using STATA software.
Results: The recovery rate was 97.2% (1,436/1,476). The cumulative incidence of AD was significantly higher in the infants without sunlight exposure over the first 6 months of life compared with the unexposed infants (25.0% vs 5.68%; P = .030), also in the infants with FH (30.0% vs 5.95%; P = .021). The cumulative incidence of AD was significantly higher in males without sunlight exposure during each timing compared with unexposed males (28.6% vs 6.5%; P = .013: 60.0% vs 6.6%; P = .003: 40.0% vs 6.3%; P = .039), but not in females.
Conclusions: Gender- and genetic-dependently, sunlight exposure might affect the susceptibility to infections mediated by innate immunity in the skin, and then modulate the risk of AD in infants.