Figure 2. Potential factors contributing to sensitization to foods.

Environmental factors may provide an increased or decreased risk for the development of allergic sensitization to foods. The gut microbiota has been shown to suppress allergy by decreasing IgE, decreasing allergic effector cells (basophils), and increasing Tregs in the intestine. Nutritional factors may either suppress or promote allergy. Data show that vitamin A and D may promote tolerance or suppress allergy, as do long chain fatty acids (FA) and aryl hydrocarbon receptor (AHR) ligands. In contrast, high fat diet and medium chain trigylcerides (TG) promote allergy. Exposure to food allergens through non-oral routes such as the skin may predispose to sensitization, particularly in the context of genetic barrier defects or inflamed skin. Inflamed skin produces cytokines that change the phenotype of the dendritic cell and promote Th2 polarization. Allergens themselves can activate innate immune responses in dendritic cells to promote Th2 polarization.