Food protein-induced allergic proctocolitis (AP), the earliest identified form of non-IgE-mediated food allergy in infants, occurs at the mucosal surface where dietary proteins, intestinal microbes, and immune cells directly interact, and increases the risk for life threatening IgE-mediated food allergy, making it an important model for understanding early food allergic disease development. The gene discussed is IGHE; the disease is food allergy.