Food allergy and gut microbiota

Food allergies (FAs) reflect a hypersensitivity state induced by food allergens. Approximately 10% of the world's children and 4% of adults experience FAs, therefore the condition is highly prevalent with the gut microbiota having distinct roles. Potentially emanating from different intestinal flora fermentation products, FAs are modulated by diets via intestinal flora and postbiotics. In this article, we systematically reviewed immunoglobulin E mechanisms in FAs, intestinal microorganism structures, microbiota mechanisms alleviating FAs, and summarized putative mechanisms alleviating FA dietary components. Imbalanced helper T cell (Th)1/Th2 and regulatory T cells/Th17 cause FAs, while Enterotypes, Firmicutes/Bacteroidetes, and Enterobacteriaceae/Bacteroidaceae ratios, and other genera are altered after FAs. Moreover, the microbiota alleviate FAs three ways via direct access, bile acid (BA) pool maintenance, and postbiotic generation. (1) FAs are alleviated by functional carbohydrates that are metabolized as short-chain fatty acids (SCFAs), which modulate microbiota and metabolites, interact with toll-like receptor 4 (TLR4), and promote BA excretion. (2) FAs are alleviated by dietary proteins that generate tryptophan metabolites, modulate microbiota and metabolites, generate anti-proteins which promote BA excretion, and FA are double change by the protein after maillard reaction via changing allergen sensitization and microbiota. (3) FAs are induced by high-fat diets (HFDs) and alleviated by omega3/6 ratios. (4) FAs are alleviated by dietary polyphenols from modulated microbiota, strengthened intestinal barrier, reduced allergen sensitization, and regulated immune cells. In this review, we provide a scientific basis for personalized and accurate diet design in preventing and alleviating FAs.