Which immunoglobulin is involved in a typical food allergy?

• A. IgG
• B. IgA
• C. IgM
• D. IgE

Answer: (D)

In a typical food allergy, the reaction is IgE-mediated. When a person is sensitized, the immune system makes allergen-specific IgE antibodies that bind to mast cells and basophils. At first exposure, nothing dramatic happens, but on subsequent exposure the allergen cross-links these bound IgE molecules, triggering degranulation of the cells and release of histamine and other mediators. This release causes the classic allergic symptoms such as itching, hives, swelling, abdominal pain, or in severe cases anaphylaxis.

Other immunoglobulins have different roles: IgG is mainly involved in secondary immune responses and opsonization, IgA protects mucosal surfaces, and IgM is the first antibody produced in an initial response. They are not the primary drivers of the typical immediate food-allergy reaction, which is why IgE is the correct choice.