Q.Allergy involves :

Allergic (immediate hypersensitivity) reactions are mediated by IgE antibodies.

When an allergen (like pollen or dust) first enters a sensitive individual, B cells produce IgE antibodies specific to that allergen; these IgE molecules bind to receptors on mast cells and basophils. On subsequent exposure to the same allergen, cross-linking of bound IgE triggers degranulation of these cells, releasing histamine and other inflammatory mediators that cause the classic allergy symptoms (sneezing, watery eyes, breathlessness). Option (a) IgA is the main antibody found in secretions (saliva, tears, mucus) providing mucosal defence, not typically the allergy mediator. Option (c) IgM is the first antibody produced in a primary immune res …