Anaphylaxis: recognition & treatment

Stepwise recognition, first-line IM epinephrine, positioning, escalation, tryptase, and disposition. Links the IM epinephrine dose, Ring-Messmer grading, tryptase 20%+2, REMA, WHO/ICC SM criteria, and neffy-weight calculators.

Evidence tier: Guideline-derived.

Decision points

Meets anaphylaxis criteria?
Response to treatment?
High biphasic / extended-monitoring risk?
Obtain tryptase?

Do-not-miss pitfalls

Do not use isolated urticaria as automatic anaphylaxis unless multisystem or severe features exist.
Do not delay epinephrine for antihistamines or corticosteroids.
Normal tryptase does not rule out anaphylaxis, especially food-triggered reactions.
Do not assume a first known exposure excludes anaphylaxis, prior unrecognized sensitization can occur.
Avoid blanket discontinuation of beta-blockers/ACE inhibitors without weighing cardiovascular risk.
Sitting or standing a patient in shock can cause fatal pulseless electrical activity, keep supine with legs elevated until fully stable.
Corticosteroids are NOT reliably effective for preventing biphasic anaphylaxis; the 2023 parameter removed the recommendation.
IV epinephrine outside a monitored setting carries high risk of fatal arrhythmia, use IM route until continuous cardiac monitoring is established.
Alpha-galactose (α-gal) syndrome causes delayed anaphylaxis 2-6 h after red meat in patients sensitized by lone star tick bites, onset during sleep is a clue; do not label as idiopathic without asking about tick exposure and meat timing.
Scombroid fish poisoning (improperly refrigerated tuna, mackerel, mahi-mahi) produces histamine-mediated flushing, urticaria, and vomiting that mimic anaphylaxis, epinephrine is safe to give if uncertain, but the reaction is not IgE-mediated and will not recur with future fish exposure.
Protracted anaphylaxis (symptoms persisting >4 h despite initial epinephrine) is distinct from biphasic reaction, often signifies persistent allergen exposure or inadequate treatment and typically requires IV epinephrine infusion and ICU-level monitoring.

Evidence & citations

Clinician decision support. Verify against the cited source. Not a substitute for clinical judgment. 100% on-device; no patient data is stored or transmitted.