The foreign substance responsible for causing an allergic reaction is called a(n):

The foreign substance responsible for causing an allergic reaction is called a(n):

• A. Antibody
• B. Allergen
• C. Mediator
• D. Antigen

Answer: (B)

Allergic reactions start when the body encounters a foreign substance that it recognizes as an allergen and mounts an immune response to it. An allergen is the substance that triggers the reaction, such as pollen or pet dander. Allergens are a subset of antigens—the broader category of things that can provoke an immune response—but only these specific antigens provoke an allergic, IgE-mediated reaction. An antibody is the immune protein produced to recognize the allergen, while a mediator is a chemical released during the reaction (like histamine) that causes symptoms. Antigen simply means any substance capable of provoking an immune response, not necessarily one that causes allergy.

Allergic reactions start when the body encounters a foreign substance that it recognizes as an allergen and mounts an immune response to it. An allergen is the substance that triggers the reaction, such as pollen or pet dander. Allergens are a subset of antigens—the broader category of things that can provoke an immune response—but only these specific antigens provoke an allergic, IgE-mediated reaction. An antibody is the immune protein produced to recognize the allergen, while a mediator is a chemical released during the reaction (like histamine) that causes symptoms. Antigen simply means any substance capable of provoking an immune response, not necessarily one that causes allergy.