Which term describes an immune system overreaction?

• A. Blood pressure
• B. Sunscreen
• C. Concussion
• D. Allergy

Answer: (D)

The immune system overreacts when it treats something harmless as a threat. An allergy is exactly that situation: the body mounts a strong immune response to normally harmless substances like pollen, foods, or pet dander. This involves IgE antibodies and the release of histamine from mast cells, which causes symptoms such as itching, sneezing, swelling, or hives, and can be more severe in rare cases. The other terms aren’t immune reactions: blood pressure is a measure of the force of blood against artery walls; sunscreen is a protective layer to block UV radiation; and a concussion is a brain injury from a bump or blow. So, allergy is the term that describes an immune system overreaction.