Is there a rationale for supplementing with vitamin D patients under treatment with allergen immunotherapy?

Vitamin D (VD) has been shown to exert immunomodulatory activities, especially in promoting immune tolerance. For these properties VD has been proposed in the therapy of immunological conditions in which the loss of tolerance is the key pathogenetic aspect of the disease, such as allergies. Despite these properties available literature suggests VD is not useful in treating or preventing allergic diseases and whether low serum VD levels favor allergic sensitization and severity is debated. The level of VD is one of the many conditions that can influence allergic sensitization and therefore only a multivariate analysis on a numerically adequate cohort of patients, that considers all the factors that can favor allergy, would be able to assign the weight of each variable and determine the extent to which VD inhibits allergic sensitization and march. On the contrary, VD is able to potentiate the antigen-specific tolerogenic response induced by Allergen Immunotherapy (AIT) as demonstrated by the large majority of studies. In our experience, the association of VD and Sublingual AIT (LAIS, Lofarma, Italy) gave an excellent clinical and immune response in particular enhancing the differentiation of memory T regulatory cells. While waiting for a more extensive literature, VD/AIT combination should be always performed in treating allergies. In any case, the assessment of the level of VD should become a routine in allergic patients with an indication to AIT as, in case of VD deficiency or insufficiency, VD seems a particularly active adjuvant to the immune treatment.