Allergies are best described as?

• A. A deficiency in immune response
• B. Having a hypersensitivity to a substance that does not normally cause a reaction
• C. A bacterial infection of the immune system
• D. An autoimmune attack on host tissues

Answer: (B)

Allergies involve a hypersensitivity reaction to a substance that is normally harmless. In susceptible individuals, the immune system makes IgE antibodies to the allergen, and on re-exposure these antibodies trigger release of histamine from mast cells and basophils, causing symptoms such as itching, sneezing, swelling, or wheezing. This is not a deficiency in immune response, not a bacterial infection, and not an autoimmune attack on the body’s own tissues. Therefore, describing allergies as a hypersensitivity to a normally harmless substance best captures what’s happening.