We discussed various physiological and pathological situations in which the epithelial permeability to food antigens is degraded. Most of the changes observed are quantitative, and alter the degradative and direct transport pathways. How these changes in permeability lead to oral tolerance, systemic immune response, or hypersensitivity is a question that remains to be answered. Bearing in mind that enterocytes may function as antigen‐presenting cells, intracellular processing during epithelial transport might play a major role in initiating the immune response, and conversely, lymphoepitheliai interactions might be one of the keys to the regulation of intestinal epithelial function.