IGHE and IgE responsiveness, atopic: The subsequent release of histamine and other downstream mediators leads to symptoms of anaphylaxis through a type I hypersensitivity reaction-a rapid, IgE-mediated immune response that occurs when allergens cross-link IgE antibodies bound to mast cells and basophils, triggering their degranulation and the release of inflammatory substances. FDEIA is characterized by an immediate type I hypersensitivity reaction that occurs only when a trigger food is consumed in close temporal proximity to exercise.