What is the treatment algorithm for an allergic reaction?

Treatment Algorithm for Allergic Reactions

Epinephrine is the first-line treatment for moderate to severe allergic reactions, and should be administered immediately when anaphylaxis is suspected. 1

Classification of Allergic Reactions

Allergic reactions can be classified according to severity using the modified Ring and Messmer scale:

Grade	Clinical Signs
I	Skin/mucosal signs only: generalized erythema, urticaria, angioedema
II	Moderate multi-organ involvement: skin/mucosal signs with moderate hypotension, tachycardia, moderate bronchospasm or gastrointestinal symptoms
III	Life-threatening mono- or multi-organ involvement: severe hypotension, tachycardia/bradycardia, severe bronchospasm, skin/mucosal signs, or gastrointestinal symptoms
IV	Cardiac or respiratory arrest

Treatment Algorithm

Grade I Reactions (Mild - Skin/Mucosal Involvement Only)

• H1 antihistamine: diphenhydramine 1-2 mg/kg (maximum 50 mg) orally or IV 1
• Consider H2 antihistamine: ranitidine 1-2 mg/kg (maximum 75-150 mg) orally or IV 1
• Observe for 1-2 hours for progression of symptoms
• No epinephrine required for isolated cutaneous symptoms 1

Grade II-IV Reactions (Moderate to Severe)

1. First-line treatment: Epinephrine IM

   • Adults and children >30 kg: 0.3-0.5 mg (0.3-0.5 mL of 1:1000 solution) 2
   • Children ≤30 kg: 0.01 mg/kg (0.01 mL/kg of 1:1000 solution), maximum 0.3 mg 2
   • Administer into anterolateral thigh 1
   • May repeat every 5-15 minutes as needed 1

2. Airway Management

   • Position patient appropriately
   • Administer 100% oxygen 1
   • For bronchospasm: albuterol via MDI (4-8 puffs for children; 8 puffs for adults) or nebulized solution (1.5 mL for children; 3 mL for adults) 1

3. Circulation Support

   • Place patient in recumbent position with legs elevated if hypotensive 1
   • IV fluids: rapid infusion of 10-20 mL/kg for hypotension 1
   • For refractory hypotension:
     • Consider additional epinephrine doses
     • Consider vasopressors for persistent hypotension
     • Glucagon 1-5 mg IV (adults) or 20-30 μg/kg (children, max 1 mg) for patients on beta-blockers 1

4. Adjunctive Treatments

   • H1 antihistamine: diphenhydramine 1-2 mg/kg (maximum 50 mg) IV or oral 1
   • H2 antihistamine: ranitidine 1-2 mg/kg (maximum 75-150 mg) IV or oral 1
   • Corticosteroids: prednisone 1 mg/kg (maximum 60-80 mg) oral or methylprednisolone 1 mg/kg (maximum 60-80 mg) IV 1

Observation Period

• Monitor for 4-6 hours or longer based on reaction severity 1
• Extended observation (8-24 hours) for patients with:
  • Severe initial reaction
  • History of biphasic reactions
  • Difficult access to emergency care
  • Comorbid conditions (asthma, cardiovascular disease)
  • Late evening presentation

Discharge Planning

1. Prescribe emergency medications

   • Epinephrine auto-injector prescription and training 1
   • H1 antihistamine: diphenhydramine every 6 hours for 2-3 days or non-sedating antihistamine 1
   • H2 antihistamine: ranitidine twice daily for 2-3 days 1
   • Corticosteroid: prednisone daily for 2-3 days 1

2. Patient education

   • Allergen avoidance
   • Recognition of anaphylaxis symptoms
   • Proper use of epinephrine auto-injector
   • When to seek emergency care
   • Medical identification jewelry or anaphylaxis wallet card 1

3. Follow-up

   • Arrange follow-up with primary care provider
   • Consider referral to allergist/immunologist 1

Important Clinical Considerations

• Do not delay epinephrine administration for moderate to severe reactions - it is the most important intervention to prevent mortality 3
• Do not inject epinephrine into buttocks, digits, hands, or feet 2
• Patients with asthma, mast cell disorders, cardiovascular disease, and those taking beta-blockers or ACE inhibitors are at higher risk for severe reactions 1
• Biphasic reactions can occur up to 72 hours after the initial reaction 4
• For patients on beta-blockers with refractory hypotension, glucagon may be effective 1
• Antihistamines and corticosteroids should never be used as first-line treatment or in place of epinephrine for anaphylaxis 3

By following this algorithm, clinicians can effectively manage allergic reactions of varying severity while prioritizing interventions that reduce morbidity and mortality.