What is the role of steroids, such as prednisone, in treating allergic reactions?

Role of Steroids in Allergic Reactions

Steroids such as prednisone play a limited adjunctive role in allergic reactions—they are NOT effective for acute symptom relief but are recommended after anaphylaxis to potentially prevent biphasic reactions, despite weak supporting evidence. 1

Acute Treatment: Steroids Are NOT First-Line

Critical Limitation: Delayed Onset of Action

• Corticosteroids are not helpful in treating acute anaphylaxis due to their slow onset of action (4-6 hours) and should never replace epinephrine as first-line treatment 1
• Epinephrine remains the only definitive treatment for anaphylaxis; antihistamines and steroids are purely adjunctive 1
• The most dangerous pitfall is using antihistamines or steroids instead of epinephrine, which significantly increases risk of life-threatening progression 1

When Steroids Are Used Acutely

• In refractory anaphylaxis unresponsive to repeated epinephrine and IV fluids, corticosteroids may be administered alongside vasopressors 1
• For severe presentations requiring urgent relief (severe dysphagia, dehydration, significant weight loss), systemic corticosteroids can be considered 1

Post-Reaction Management: The Primary Role

Standard Discharge Protocol After Anaphylaxis

The NIAID Expert Panel recommends prednisone 1 mg/kg daily (maximum 60-80 mg) for 2-3 days after anaphylaxis as part of discharge management 1, 2

This recommendation includes:

• H1 antihistamine (diphenhydramine every 6 hours) for 2-3 days 1
• H2 antihistamine (ranitidine twice daily) for 2-3 days 1
• Corticosteroid (prednisone daily) for 2-3 days 1

Rationale: Prevention of Biphasic Reactions

• Biphasic reactions occur in up to 20% of anaphylaxis cases, with all reported cases occurring within 3 days 1
• The mechanism involves delayed recruitment of inflammatory cells and release of long-acting mediators from mast cells 1
• However, very little data actually support corticosteroid use for preventing biphasic reactions—this is an empiric practice based on anti-inflammatory properties rather than strong evidence 1, 2

Dosing Specifics

• Adults: 1 mg/kg daily (maximum 60-80 mg) for 2-3 days 2
• Children: 1 mg/kg daily (maximum 60 mg) for 2-3 days 2
• No taper is required for these short 2-3 day courses 2

Mild Allergic Reactions

When Steroids Are NOT Needed

• Mild reactions (flushing, urticaria, isolated mild angioedema) should be treated with H1 and H2 antihistamines alone 1
• Close observation is mandatory to detect progression, at which point epinephrine must be given immediately 1
• If there is history of prior severe reaction, epinephrine should be administered early even with mild symptoms 1

Important Caveats and Pitfalls

Rare But Real: Steroid Allergy

• Paradoxically, corticosteroids themselves can cause hypersensitivity reactions ranging from contact dermatitis to anaphylaxis, though this is rare (0.3% incidence) 3, 4, 5
• Both immediate and delayed-type reactions have been documented 4, 6, 7
• Consider steroid allergy if dermatitis worsens with topical steroid therapy or systemic reactions occur after steroid administration 4, 6, 8

Infection Risk

• Corticosteroids suppress immune function and increase infection risk, including reactivation of latent tuberculosis, hepatitis B, and fungal infections 3
• For short 2-3 day courses post-anaphylaxis, this risk is minimal but should be considered in immunocompromised patients 2

Other Contraindications

• Use with caution in recent myocardial infarction due to association with left ventricular free wall rupture 3
• Monitor for hyperglycemia, hypertension, and electrolyte disturbances even with short courses 3

Clinical Algorithm

For Anaphylaxis:

1. Immediate IM epinephrine (first-line, life-saving)
2. Transfer to emergency facility
3. Observe 4-6 hours minimum
4. At discharge: prescribe prednisone 1 mg/kg daily × 2-3 days + antihistamines + epinephrine auto-injector 1, 2

For Mild Reactions:

1. H1/H2 antihistamines only
2. Close observation for progression
3. Epinephrine if any worsening 1

For Refractory Anaphylaxis:

1. Repeated epinephrine doses
2. IV fluids
3. Add corticosteroids + vasopressors
4. ICU transfer 1