What is the treatment for a common allergy reaction?

Treatment for Common Allergic Reactions

Epinephrine is the first-line treatment for severe allergic reactions (anaphylaxis), while antihistamines are appropriate for mild to moderate allergic reactions. 1, 2

Treatment Algorithm Based on Severity

Mild to Moderate Allergic Reactions

For common mild allergic reactions (hives, itching, sneezing, mild swelling):

• First-line treatment: H1 antihistamines

  • Diphenhydramine (Benadryl): 1-2 mg/kg per dose, maximum 50 mg orally every 6 hours 3
  • Alternative: Non-sedating second-generation antihistamines (cetirizine, loratadine)

• Adjunctive treatment (if needed):

  • H2 antihistamines: Ranitidine 1-2 mg/kg per dose, maximum 150 mg twice daily 3
  • Corticosteroids: Prednisone 1 mg/kg (maximum 60-80 mg) daily for persistent symptoms 3

Severe Allergic Reactions (Anaphylaxis)

For severe reactions (difficulty breathing, throat swelling, hypotension, or involvement of multiple organ systems):

• First-line treatment:

  • Epinephrine IM (anterior-lateral thigh) 3, 1, 2
    • Adults and children ≥30 kg: 0.3-0.5 mg
    • Children <30 kg: 0.01 mg/kg
    • May repeat every 5-15 minutes if symptoms persist
  • Position patient in recumbent position with legs elevated if tolerated 3

• Adjunctive treatments:

  • Oxygen therapy (8-10 L/min via face mask) for respiratory distress 1
  • IV fluids (normal saline) for hypotension 3, 1
  • H1 antihistamines: Diphenhydramine 1-2 mg/kg (maximum 50 mg) 3, 1
  • H2 antihistamines: Ranitidine 1-2 mg/kg (maximum 150 mg) 3, 1
  • Corticosteroids: Prednisone 1 mg/kg (maximum 60-80 mg) or methylprednisolone IV 3, 1
  • Bronchodilators: Albuterol for bronchospasm 3, 1

Important Clinical Considerations

Antihistamines vs. Epinephrine

While antihistamines are commonly used for allergic reactions, they have significant limitations:

• They do not relieve all symptoms of anaphylaxis 4
• They have a slow onset of action (1-3 hours vs. <10 minutes for epinephrine) 4
• They should never substitute for epinephrine in anaphylaxis 1, 4

Common Pitfalls to Avoid

1. Delaying epinephrine administration in anaphylaxis can lead to fatal outcomes 1
2. Using antihistamines alone for severe reactions instead of epinephrine 4
3. Failing to place patients in recumbent position during anaphylaxis 3, 1
4. Discharging patients too early - monitor for at least 4-6 hours due to risk of biphasic reactions 1
5. Not providing epinephrine auto-injector prescriptions at discharge for patients with history of anaphylaxis 3, 1

Follow-up Care

For patients treated for allergic reactions:

• Continue H1 antihistamines, H2 antihistamines, and corticosteroids for 2-3 days 3, 1
• Provide education on allergen avoidance 3
• Consider referral to an allergist for comprehensive evaluation, especially after severe reactions 1
• Prescribe epinephrine auto-injectors (2 doses) with proper training for patients with history of anaphylaxis 3, 1

The most recent guidelines emphasize that epinephrine remains underutilized in anaphylaxis despite being the definitive life-saving treatment, while antihistamines remain appropriate for milder allergic manifestations 1, 4.