Effect of solar irradiation on serum specific immunoglobulin E to house-dust mite

Background: The relationship between sensitization to Dermatophagoides species and solar irradiation, as reflected by vitamin D, remains elusive. Objective: We investigated the lag time and the cumulative and maximum effects of exposure to solar irradiation on sensitization to house-dust mites. Methods: A time series study design was applied to solar irradiation (MJ/m(2)) and relative humidity (%) for specific immunoglobulin E (IgE) levels against Dermatophagoides pteronyssinus (n = 20,451) and Dermatophagoides farinae (n = 22,824). We used the distributed lag nonlinear model to assess the difference of log IgE to house-dust mites in relation to climate variables. Results: Compared with specific IgE levels of those exposed to 18 MJ/m(2), the maximum increase in sensitization to D. pteronyssinus was observed at a solar irradiation of 10 MJ/m(2) at peak 0 week (difference of log IgE 0.368 [95% confidence interval (CI), 0.209-0.529], p < 0.001), and this increase continued for 3 weeks. The IgE level was significantly affected by the relative humidity of the 3rd- to 12th-lag week, and the effect reached its peak at 75% on the 8th week (difference of log IgE 0.394 [95% CI, 0.221-0.566], p < 0.001). The logistic regression analysis showed that solar irradiation was associated with a decreased risk to sensitization to D. pteronyssinus (odds ratio 0.988 per 1 MJ/m(2) [95% CI, 0.979-0.997], p < 0.013) on the testing week after controlling for humidity and temperature. Conclusion: This study demonstrated that low solar irradiation immediately increased the risk of sensitization to two house-dust mite species. Further research is warranted to delineate the underlying mechanism of the effect of solar irradiation on aeroallergen sensitization.