Which type of antibodies are involved in allergic reactions?

• A. IgG antibodies
• B. IgE antibodies
• C. IgA antibodies
• D. IgM antibodies

Answer: (B)

Allergic reactions are driven by IgE antibodies. These antibodies bind to allergens and attach to high-affinity FcεRI receptors on mast cells and basophils. When the same allergen is encountered again, it cross-links the IgE on these cells, triggering degranulation and release of histamine and other mediators that produce the classic symptoms of allergy, such as itching, swelling, and bronchoconstriction. Other antibody classes have different roles—IgG is involved in opsonization and immune complex formation, IgM is an early responder, and IgA provides mucosal protection—so they are not the primary mediators of the immediate allergic reaction.