Allergic immunotherapy takes months to achieve clinical response because it reduces which circulating antibody?

• A. Decrease in allergen-specific IgE
• B. Immediate histamine blockade
• C. Rapid increase in eosinophils
• D. No effect on IgE

Answer: (A)

Allergen immunotherapy reshapes the immune response to reduce sensitivity to the allergen over time. The clinical improvement that appears after months mainly comes from a gradual decrease in circulating allergen-specific IgE, which is the antibody that sits on mast cells and basophils and triggers histamine release when the allergen is encountered. As IgE levels fall and blocking antibodies like IgG4 rise, there is less degranulation and fewer inflammatory mediators released on exposure, so symptoms lessen. Immediate histamine blockade would provide quick relief but isn’t how immunotherapy produces its benefits, and increasing eosinophils would worsen inflammation. There is indeed a change in IgE with successful immunotherapy, making it the best explanation.