Which antibody is primarily responsible for allergic reactions?

The primary antibody responsible for allergic reactions is IgE. This immunoglobulin plays a crucial role in the body's immune response, particularly in hypersensitivity reactions. When an allergen is encountered, sensitized B cells produce IgE antibodies that bind to the surface of mast cells and basophils. Upon subsequent exposure to the same allergen, these cells release chemical mediators, such as histamine, which lead to the symptoms associated with allergies, such as itching, swelling, and inflammation.

In contrast, IgA primarily protects mucosal surfaces; IgG is the most abundant antibody in circulation and is involved in the secondary immune response, while IgM is the first antibody produced during an initial immune response. Therefore, while all of these immunoglobulins play important roles in the immune system, IgE is specifically linked to the mechanisms underlying allergic reactions.