Which statement best defines anaphylaxis?

• A. Mild reaction with no hypotension
• B. Moderate reaction with only GI symptoms
• C. Moderate/severe reaction meeting criteria: exposure to known or likely allergen with hypotension OR respiratory compromise; or two or more of the following after exposure: skin/mucosal changes, respiratory compromise, hypotension or shock, persistent GI symptoms
• D. No reaction

Answer: (C)

Anaphylaxis is a rapid, life‑threatening allergic reaction that involves more than one body system after exposure to an allergen. It is diagnosed when there is exposure to a known or likely allergen and either: hypotension or respiratory compromise, or two or more of the following after exposure: skin/mucosal changes, respiratory compromise, hypotension or shock, or persistent gastrointestinal symptoms. This is why the correct statement is best: it captures the need for systemic involvement and potential airway or circulation compromise, not just a mild localized reaction or isolated GI symptoms. Mild reactions lacking hypotension or respiratory involvement, or symptoms confined to a single system, do not meet the criteria for anaphylaxis. No reaction is obviously incorrect.