Should I give my patient steroids or antihistamines for facial swelling and shortness of breath (SOB)?

Immediate Treatment: Epinephrine First, Then Adjunctive Therapy

For a patient presenting with facial swelling and shortness of breath concerning for anaphylaxis, you must administer intramuscular epinephrine immediately as first-line treatment—antihistamines and corticosteroids are only adjunctive therapies that should never delay or replace epinephrine. 1, 2

Why Epinephrine is Non-Negotiable

• Epinephrine is the only medication proven to prevent death in anaphylaxis through its critical vasoconstrictor effects (preventing airway edema and shock), bronchodilator effects, and cardiac support 1
• Delayed epinephrine administration is directly associated with fatal outcomes, while prompt prehospital epinephrine reduces hospitalization risk and mortality 1, 2, 3
• The 2020 American Heart Association guidelines explicitly state: "There is no proven benefit from the use of antihistamines, inhaled beta agonists, and IV corticosteroids during anaphylaxis-induced cardiac arrest" 1

Epinephrine Dosing Protocol

• Administer 0.3-0.5 mg of epinephrine (1:1000) intramuscularly into the anterolateral thigh (vastus lateralis) for adults 1
• Repeat every 5-15 minutes as needed if symptoms persist or progress 1, 2
• If IV access is established and the patient is in shock, consider IV epinephrine 0.05-0.1 mg (1:10,000 solution), though IM remains preferred initially 1

Role of Antihistamines (Adjunctive Only)

Antihistamines should only be given AFTER epinephrine, never as a substitute or first-line treatment 1, 2:

• H1 antihistamines (diphenhydramine 25-50 mg IV/oral or cetirizine 10 mg) only relieve itching and urticaria—they do NOT treat airway swelling, bronchospasm, hypotension, or shock 1, 2
• H2 antihistamines (ranitidine or famotidine) can be added to H1 blockers, though evidence supporting this combination in acute anaphylaxis is minimal 1, 2
• Recent registry data (5,364 cases) showed patients receiving prehospital antihistamines had slightly better outcomes, but this effect was far weaker than epinephrine's impact 3

Role of Corticosteroids (Limited and Delayed)

Corticosteroids have NO role in acute anaphylaxis management due to their 4-6 hour onset of action 1, 2:

• They are given empirically (prednisone 1 mg/kg, maximum 60-80 mg orally, or methylprednisolone 100 mg IV) to potentially prevent biphasic reactions occurring up to 72 hours later 1, 2
• Importantly, registry data showed patients receiving prehospital corticosteroids were MORE likely to require IV fluids and hospital admission, suggesting they may be markers of severe reactions rather than beneficial treatments 3
• Corticosteroids are effective only for inflammatory airway edema from direct injury (surgical/thermal), NOT for mechanical edema from anaphylaxis 1

Critical Management Algorithm

1. Recognize anaphylaxis: Acute onset with skin/mucosal involvement (facial swelling) PLUS respiratory compromise (shortness of breath) 1, 2

2. Immediate epinephrine IM (0.3-0.5 mg in anterolateral thigh) 1, 2

3. Position patient supine (or sitting if respiratory distress severe) and assess airway, breathing, circulation 1

4. Establish IV access and give fluid bolus (Ringer's lactate 10-20 mL/kg) if hypotension present 2

5. Administer supplemental oxygen and prepare for advanced airway management if airway swelling progresses 1

6. Only after epinephrine: Give H1 antihistamine (diphenhydramine 25-50 mg) and consider H2 blocker 1, 2

7. Consider corticosteroids (methylprednisolone 100 mg IV) for potential biphasic reaction prevention 1, 2

8. Monitor for 4-12 hours for biphasic reactions, with longer observation for severe presentations 2, 4

Common Pitfalls to Avoid

• Never substitute antihistamines or corticosteroids for epinephrine—this is the most common fatal error 1, 2
• Do not delay epinephrine while obtaining IV access or giving other medications 2, 5
• Do not give only 2 puffs of albuterol thinking it equals a treatment—if bronchodilators are needed, give 6-10 puffs with spacer or nebulized treatment, but only as adjunct to epinephrine 1
• Do not discharge without observing for biphasic reactions, which occur in up to 20% of cases 1, 2
• Do not forget to prescribe epinephrine auto-injector (2 doses) with proper training before discharge 2

Special Considerations

• If patient is on beta-blockers and not responding to epinephrine, administer glucagon 1-5 mg IV as it bypasses beta-receptors 2
• Prepare for surgical airway if rapid oropharyngeal/laryngeal edema develops despite treatment 1