A 35-year-old man with a history of severe asthma presents with acute onset of pruritus, erythematous rash over the trunk and extremities, and mild dyspnea 20 minutes after eating shellfish at a restaurant. He has no prior documented shellfish allergy. Vital signs are stable; oxygen saturation is 96% on room air. Physical examination shows urticaria and mild wheezing. What is the most appropriate immediate next step in management?

Question

Accepted Answer

A. Administer IM epinephrine 0.3 mg 1:1000 immediately and establish IV access. ## Clinical Context

This is **Type I hypersensitivity (IgE-mediated food allergy)** with early systemic manifestations:
- Rapid onset (20 minutes post-ingestion)
- Urticaria + respiratory involvement (wheezing)
- **Key risk factor:** Pre-existing asthma significantly increases risk of severe/fatal anaphylaxis

**High-Yield:** Patients with asthma who develop food allergy symptoms have a **higher risk of biphasic anaphylaxis and fatal outcomes**. They require more aggressive early intervention.

## Why This Patient Needs IM Epinephrine Now

```mermaid
flowchart TD
  A[Food allergy + urticaria + wheezing]:::outcome --> B{Asthma present?}:::decision
  B -->|Yes| C[HIGH RISK for progression]:::urgent
  C --> D[Give IM Epinephrine 0.3 mg 1:1000]:::action
  B -->|No| E{Symptoms limited to skin?}:::decision
  E -->|Yes| F[Oral antihistamine + observe]:::action
  E -->|No| G[IM Epinephrine]:::action
  D --> H[IV access, monitor 4-8 hrs]:::action
  F --> I[Discharge if stable after 1 hr]:::action
```

**Key Point:** Presence of **asthma + any respiratory symptom (even mild wheezing) = indication for IM epinephrine**, regardless of blood pressure or severity of other symptoms.

**Clinical Pearl:** Oral antihistamines work slowly (30–60 minutes) and do not prevent progression to severe anaphylaxis. In a patient with asthma and respiratory involvement, waiting for oral medication to work is dangerous.

**Warning:** Do NOT delay epinephrine while waiting for test results or assuming symptoms will plateau. Biphasic reactions (symptom recurrence 4–12 hours later) are common and can be fatal.

## Management Hierarchy for Food Allergy with Respiratory Symptoms

| Scenario | Action |
|----------|--------|
| Urticaria only, no asthma | Oral antihistamine ± observe |
| Urticaria + asthma, any respiratory sign | IM epinephrine |
| Angioedema or stridor | IM epinephrine immediately |
| Hypotension or shock | IM epinephrine + IV fluids |

**Mnemonic: RAMP** — **R**espiratory symptoms, **A**sthma history, **M**ultiple triggers, **P**rior anaphylaxis → all lower the threshold for epinephrine use.

[cite:Robbins 10e Ch 6; Harrison 21e Ch 317]

Answer

B. Perform serum tryptase level and specific IgE testing to shellfish

Answer

C. Administer oral antihistamine (cetirizine 10 mg) and observe in clinic for 1 hour

Answer

D. Prescribe an epinephrine auto-injector and discharge home with strict shellfish avoidance

Explanation

Clinical Context

Why This Patient Needs IM Epinephrine Now

Management Hierarchy for Food Allergy with Respiratory Symptoms

Practice similar questions

Join our NEET PG community