How quickly do anaphylactic reactions typically occur after exposure?

• A. Immediately after exposure.
• B. Within minutes of exposure.
• C. Within hours of exposure.
• D. Days after exposure.

Answer: (B)

Anaphylaxis is an immediate IgE-mediated hypersensitivity reaction. When the allergen is encountered, it cross-links IgE on mast cells and basophils, triggering a rapid release of mediators like histamine. This causes symptoms such as swelling, hives, wheezing, and potential drop in blood pressure that appear within minutes. Because this fast cascade unfolds right after exposure, the timing is best described as occurring within minutes. While rare cases of very early or biphasic onset can occur, delays of hours or days are not typical for true anaphylaxis, and “immediately” is too absolute for most real-world scenarios.