What is the treatment for an allergic reaction in the emergency room (ER)?

Emergency Treatment of Allergic Reactions in the ER

The first-line treatment for allergic reactions in the emergency room is intramuscular (IM) epinephrine, which should be administered promptly as the cornerstone of management for anaphylaxis. 1

Initial Assessment and Management

Severity Assessment

• Mild reactions: Localized hives, mild itching, mild swelling
• Severe reactions/Anaphylaxis: Any of the following:
  • Respiratory symptoms (stridor, wheezing, shortness of breath)
  • Cardiovascular symptoms (hypotension, tachycardia)
  • Widespread urticaria or angioedema
  • GI symptoms (vomiting, diarrhea, abdominal cramps)
  • Altered mental status

Immediate Actions for Anaphylaxis

1. Administer epinephrine IM into the anterolateral thigh 1

   • Adults and children ≥30 kg: 0.3-0.5 mg (0.3-0.5 mL of 1:1000 solution)
   • Children <30 kg: 0.01 mg/kg, maximum 0.3 mg
   • May repeat every 5-15 minutes if symptoms persist 1, 2

2. Position patient appropriately

   • Place in recumbent position with legs elevated if tolerated 1
   • This improves venous return and cardiac output

3. Call for help/activate emergency response system 1

Secondary Interventions

After epinephrine administration, implement these additional measures:

Airway and Breathing

• Provide supplemental oxygen if needed 1
• Monitor oxygen saturation
• For bronchospasm not responding to epinephrine, administer inhaled albuterol 1

Circulation

• Establish IV access
• Administer IV fluids for hypotension (10-20 mL/kg bolus) 1
• Monitor vital signs every 5-15 minutes until stable

Medications (Adjunctive Therapy)

• H1 antihistamines (e.g., diphenhydramine 25-50 mg IV/IM/PO) 1, 3

  • Note: These are second-line agents and should not replace epinephrine
  • Only relieve itching and urticaria, not respiratory symptoms or shock

• H2 antihistamines (e.g., ranitidine)

  • May be used in combination with H1 antihistamines
  • Should not be used without H1 antihistamines 1

• Corticosteroids (e.g., methylprednisolone 1-2 mg/kg IV)

  • May help prevent biphasic or protracted reactions
  • Slow onset of action; not effective for acute symptoms 1

Special Considerations

Refractory Anaphylaxis

• If no response to IM epinephrine and fluid resuscitation:
  • Consider IV epinephrine (1:10,000 solution) 1
  • Consider additional vasopressors (e.g., dopamine, norepinephrine) 1, 4
  • For patients on beta-blockers, consider glucagon (1-5 mg IV over 5 minutes, followed by infusion) 1

Monitoring

• Continue monitoring for at least 4-6 hours after symptom resolution
• Longer observation may be needed for severe reactions or those requiring multiple doses of epinephrine 5
• Monitor for biphasic reactions (recurrence of symptoms after initial resolution)

Common Pitfalls to Avoid

1. Delaying epinephrine administration - This is associated with increased mortality and morbidity 1
2. Using antihistamines or corticosteroids as first-line treatment - These medications do not treat respiratory or cardiovascular symptoms and have a delayed onset of action 1
3. Administering epinephrine subcutaneously instead of intramuscularly - IM administration provides more rapid and reliable absorption 1
4. Discharging patients too early - Patients should be observed for potential biphasic reactions 4
5. Not prescribing epinephrine auto-injectors at discharge - Patients with anaphylaxis should be prescribed auto-injectors and educated on their use 1

Discharge Planning

• Prescribe epinephrine auto-injector(s) 1
• Provide patient education on:
  • Proper use of auto-injector
  • Allergen avoidance
  • Recognition of symptoms
  • When to seek emergency care
• Refer to an allergist for follow-up and consideration of immunotherapy if appropriate 1
• Consider multiple epinephrine devices for patients with history of severe anaphylaxis or those who have required multiple doses previously 5