Anaphylaxis vs Angioedema
How to tell Anaphylaxis and Angioedema apart when a board question makes them look alike.
Step 2 CK pairs are in open beta while clinical review finishes. Spot an issue? Tell us.
Urticaria with bronchospasm or hypotension indicates anaphylaxis and immediate epinephrine need.
Side by side
Hypotension or bronchospasm with urticaria minutes after exposure indicates anaphylaxis.
Isolated nonpruritic facial or tongue swelling without urticaria in an ACE inhibitor user suggests bradykinin-mediated angioedema.
IgE-mediated mast-cell degranulation releases histamine causing vasodilation, capillary leak, and bronchoconstriction.
Bradykinin accumulation increases vascular permeability without histamine-driven urticaria.
Diagnosis is clinical, but elevated serum tryptase within 1 to 3 hours can support anaphylaxis after stabilization.
ACE inhibitor angioedema has normal tryptase and often no eosinophilia; C4 is low in hereditary C1 inhibitor deficiency states.
The trap
Treating presumed angioedema first with antihistamines alone delays life-saving epinephrine in anaphylaxis. The presence of wheeze, hypotension, or diffuse hives should trigger intramuscular epinephrine immediately.
The repair move
Next best step: give IM epinephrine 0.3 to 0.5 mg of 1 mg/mL solution in the lateral thigh now, repeat every 5 to 15 minutes as needed, start high-flow oxygen and IV crystalloids, and prepare airway support early. For ACE inhibitor angioedema without anaphylaxis signs, secure airway and consider C1 esterase inhibitor concentrate or fresh frozen plasma.
Try a free question
CoreA 24-year-old man develops hypotension, wheeze, and diffuse hives after a bee sting. What is the next best step in management?
Show answer and explanation
Answer: A. IM epinephrine 0.3 to 0.5 mg immediately. Anaphylaxis requires immediate intramuscular epinephrine as first-line treatment.
Why the other choices are tempting
- B. Wrong. Antihistamines are adjuncts and do not treat shock or airway compromise.
- C. Wrong. Bronchodilator alone misses systemic vasodilatory collapse.
- D. Wrong. Steroids are delayed adjuncts, not immediate rescue.
- E. Wrong. Treatment should never be delayed for confirmatory lab testing.
Flashcards
Tap a card to flip it.
Which finding makes immediate epinephrine mandatory in allergic presentations?
Any airway compromise, bronchospasm, or hypotension with likely allergen exposure.
What clinical clue supports bradykinin-mediated angioedema over anaphylaxis?
Nonpruritic swelling without hives, often in ACE inhibitor users.
Quick answers
What is the fastest way to tell Anaphylaxis from Angioedema?
Urticaria with bronchospasm or hypotension indicates anaphylaxis and immediate epinephrine need.
What is the key clue for Anaphylaxis?
Hypotension or bronchospasm with urticaria minutes after exposure indicates anaphylaxis.
What is the key clue for Angioedema?
Isolated nonpruritic facial or tongue swelling without urticaria in an ACE inhibitor user suggests bradykinin-mediated angioedema.
What is the common trap with Anaphylaxis vs Angioedema?
Treating presumed angioedema first with antihistamines alone delays life-saving epinephrine in anaphylaxis. The presence of wheeze, hypotension, or diffuse hives should trigger intramuscular epinephrine immediately.