The role of vitamin D in allergic rhinitis.

Recent studies suggest that vitamin D is related to allergic rhinitis (AR). In this review, we first discuss the physiology and metabolism of vitamin D, then we review the function of vitamin D in the immune system, and above all, we highlight the current research regarding the role of vitamin D in AR. Finally, we find that there are both experimental and clinical studies showing that vitamin D is associated with AR, although the results are not consistent and even conflicting. Evidences from those clinical studies show a slightly tendency that serum vitamin D level might be inversely associated with the risk of AR. Meanwhile, it seems that gender and age may influence the relationship between vitamin D and AR. However, because of the heterogeneity in defining AR, differences in study design and so on, all these findings need to be confirmed by further studies. Additional clinical studies as well as experimental research are needed to better understand how vitamin D influences AR.