What is the treatment for an allergic reaction?

Treatment of Allergic Reactions

The first-line treatment for anaphylaxis is intramuscular epinephrine, which should be administered immediately upon recognition of symptoms, followed by adjunctive therapies including antihistamines, corticosteroids, and bronchodilators as needed. 1

Classification and Initial Management

Mild Allergic Reactions

• For mild reactions (isolated urticaria, mild angioedema, or oral allergy syndrome):
  • H1 antihistamines: diphenhydramine 1-2 mg/kg (maximum 50 mg) or second-generation antihistamines 2, 1
  • Observe for progression to more severe symptoms
  • If history of prior severe reactions, administer epinephrine even for mild symptoms 2

Anaphylaxis

• First-line treatment: Epinephrine IM 2, 1, 3

  • 0.01 mg/kg (1:1,000 solution), maximum 0.5 mg per dose
  • Weight-based autoinjector dosing:
    • 10-25 kg: 0.15 mg epinephrine autoinjector

    • 25 kg: 0.3 mg epinephrine autoinjector

  • Administer into anterolateral thigh
  • May repeat every 5-15 minutes if needed

• Immediate actions:

  • Remove allergen if possible
  • Place patient in recumbent position with lower extremities elevated if tolerated
  • Call emergency services/transfer to emergency facility
  • Monitor vital signs

Adjunctive Treatments

Respiratory Support

• Supplemental oxygen for respiratory distress 1
• Bronchodilator (albuterol) for bronchospasm 2
  • MDI: 4-8 puffs (child), 8 puffs (adult) OR
  • Nebulized solution: 1.5 ml (child), 3 ml (adult) every 20 minutes or continuously as needed

Antihistamines (after epinephrine for anaphylaxis)

• H1 antihistamine: diphenhydramine 1-2 mg/kg (maximum 50 mg) IV, IM, or oral 2, 1
  • Oral liquid is more readily absorbed than tablets
  • Consider non-sedating second-generation antihistamines for less impairment 4
• H2 antihistamine: ranitidine 1-2 mg/kg (maximum 75-150 mg) oral or IV 2, 1

Additional Treatments for Severe Reactions

• IV fluids for hypotension: large volume normal saline 2, 1
• Corticosteroids: prednisone 1 mg/kg (maximum 60-80 mg) oral or methylprednisolone 1 mg/kg (maximum 60-80 mg) IV 2
• For refractory hypotension:
  • Vasopressors
  • Glucagon (for patients on beta-blockers): 1-5 mg IV, may repeat or follow with infusion 2, 1

Observation and Follow-up

Monitoring

• Observe for 4-6 hours after initial reaction 2
• Longer observation (possibly admission) for severe reactions due to risk of biphasic reactions 1, 5

Discharge Plan

• Prescribe epinephrine auto-injector (2 doses) 2
• Continue medications for 2-3 days after discharge 2:
  • H1 antihistamine (diphenhydramine every 6 hours or non-sedating alternative)
  • H2 antihistamine (ranitidine twice daily)
  • Corticosteroid (prednisone daily)

Patient Education

• Allergen avoidance strategies
• Recognition of anaphylaxis symptoms
• Proper use of epinephrine auto-injector
• Anaphylaxis emergency action plan
• Medical identification jewelry or wallet card
• Follow-up with primary care provider and allergist 2, 5

Special Considerations

• Delayed epinephrine administration is associated with increased mortality - do not hesitate to use 1
• Antihistamines or corticosteroids alone are insufficient for anaphylaxis treatment 1, 5
• Patients with cardiovascular disease should still receive epinephrine for anaphylaxis as benefits outweigh risks 1
• Patients on beta-blockers may have reduced response to epinephrine; consider glucagon 2, 1
• Hypersensitivity to antihistamines is rare but possible; alternative preparations may be needed 6

Risk Factors for Severe Reactions

• History of asthma (especially poorly controlled)
• Previous anaphylaxis
• Adolescents and young adults
• Peanut and tree nut allergies
• Cardiovascular disease
• Mast cell disorders 2, 1

By following this algorithmic approach to allergic reaction management, prioritizing epinephrine for anaphylaxis and using appropriate adjunctive therapies, clinicians can effectively reduce morbidity and mortality associated with these potentially life-threatening conditions.