Is gastrointestinal epithelial barrier dysfunction the only responsible for sensitization to food allergens?

Epithelial barriers are crucial defenses against pathogens and allergens, and recent theories suggest that environmental factors may compromise them, leading to type 2 inflammation and conditions such as asthma, atopic dermatitis, food allergy, and rhinitis. While skin and respiratory barriers show clear dysfunctions in allergies, the role of the gut epithelium is less defined, particularly in view of its ability to absorb nutrients and maintain immune tolerance under normal conditions. Research indicates that gastrointestinal barrier integrity typically remains preserved in food allergies, allowing for the development of immune tolerance to ingested food antigens through mechanisms like Treg cells and IgA. Allergies to cow's milk or hen's egg proteins most often resolve with age, highlighting the gut's evolving role in allergen sensitization. Studies like the LEAP (Learning Early About Peanut Allergy) trial demonstrate the preventive benefits of early allergen exposure against peanut allergy, supporting the dual allergen exposure hypothesis. New allergens such as alpha-Gal and gibberellin-regulated proteins (GRP) reveal distinct sensitization pathways beyond traditional ingestion routes, implicating non-dietary sources in allergen introduction. Altogether, there is lack of evidence suggesting that the intestinal epithelium is disrupted in food allergy.