Which term refers to a severe hypersensitivity reaction?

• A. Allergy
• B. Anaphylaxis
• C. Hypersensitivity
• D. Immunologic reaction

Answer: (B)

Anaphylaxis is a severe, systemic form of a hypersensitivity reaction. In sensitized individuals, exposure to an allergen triggers IgE-mediated release of mediators like histamine from mast cells and basophils, leading to rapid, widespread effects. Common features include skin changes such as hives or flushing and angioedema, respiratory symptoms like bronchospasm and throat tightness, and cardiovascular effects such as a sudden drop in blood pressure. This combination can progress quickly to life-threatening shock if not treated promptly, which is why anaphylaxis is the term used for the most severe hypersensitivity reaction.

Allergy refers to a broader immune response to an allergen that can be mild to moderate, not necessarily systemic or life-threatening. Hypersensitivity is the umbrella category for exaggerated immune responses, of which anaphylaxis is the most severe form. Immunologic reaction is a general phrase indicating an immune system–related response and does not specify severity.