Diagnose It Answer — April 9, 2026

24-year-old female presents via EMS approximately 10 minutes after eating at a restaurant. She is in severe respiratory distress with audible stridor, generalized urticaria covering her trunk and arms, and marked facial and lip swelling. She is agitated and clutching her throat, stating 'I can't breathe.'

Known allergy to tree nuts — carries an EpiPen but states she did not have it with her today. She ordered a salad and was told it was 'nut-free' but suspects cross-contamination. No prior anaphylactic reactions requiring hospitalization, but has had hives from accidental nut exposure in the past. No other known allergies. No current medications beyond her EpiPen.

BP 78/42 mmHg, HR 138 bpm, RR 32 breaths/min with audible stridor, SpO2 89% on room air, Temp 37.0°C. Patient is anxious, diaphoretic, and in severe distress. Angioedema visible affecting lips, tongue, and periorbital tissue. Diffuse erythematous urticarial rash with wheals present from neck to waist.

Epinephrine 0.3mg IM (1:1000) administered to left outer thigh immediately on arrival — two minutes prior per EMS. Repeat dose given in ED. 100% non-rebreather mask applied. Anesthesia called for potential emergent airway. Two large-bore IVs placed; 1L normal saline wide open. Diphenhydramine 50mg IV and methylprednisolone 125mg IV ordered. Albuterol nebulization initiated for bronchospasm.

Serum tryptase drawn (to be sent to lab — levels peak 60–90 minutes post-reaction; elevated tryptase >11.4 ng/mL confirms mast cell degranulation). ABG on 100% NRB: pH 7.38, PaO2 68 mmHg, PaCO2 34 mmHg — mild hypoxemia with compensatory hyperventilation. CBC and BMP ordered. Chest X-ray portable: hyperinflation, no consolidation, no pneumothorax. Peak flow not obtainable due to patient agitation.