Vitamin D levels and allergic diseases. An italian cross-sectional multicenter survey

Background. During the two last decades, the interest in the role of Vitamin D (VD) in allergic disease has increased. Apart from the well-known actions of VD in bone metabolism, recent studies suggested its possible role as an immune-modulator in allergy. Objective. This study, conducted over the Italian territory, evaluated the possible correlations between VD serum level and diagnosed allergic diseases (rhinitis / asthma, food allergy, atopic dermatitis). Thus, VD was assessed in patients with physician-diagnosed allergic diseases. Methods. The study was carried out in hospital- and private practice-based setting between October 2012 and March 2013, and 18 Centers participated. Only adult patients, with at least one positive skin prick test were included. The diagnostic procedures and the data collection were standardized among the centers. VD levels were assayed by the same laboratory test. Results. Three hundred and nine patients were enrolled (132 male, mean age 37.5 ± 17 years). Of them, 40% reported a positive family history for allergies (asthma / rhinitis). Rhinitis plus asthma was present in 47% of patients, atopic dermatitis in 15%, and a consistent clinical history of food allergy associated with positive skin tests was present in 25% of subjects. There was no significant association between VD level and age, sex, family history, rhinitis, or food allergy. VD levels were overall lower in patients with asthma and rhinitis, but without statistical significance. A significant difference in VD levels was detected between patient with or without atopic dermatitis. VD was not related to seasonal allergens, whereas a significant negative correlation was seen for house dust mite and dog dander. Conclusion. Our data, derived from a cross-sectional study involving only allergic patients, agree partially with the current literature. Nonetheless, the association between VD levels and allergies appeared weak. Studies involving larger samples would be required to better define the association between VD and allergies.