What is the treatment for allergic reactions?

Treatment of Allergic Reactions

Intramuscular epinephrine is the first-line treatment for anaphylaxis and severe allergic reactions and should be administered immediately at the onset of symptoms—delayed administration has been implicated in fatalities. 1, 2

Severity-Based Treatment Algorithm

Severe Reactions (Anaphylaxis)

Immediate epinephrine administration is critical:

• Adults and children ≥30 kg: 0.3-0.5 mg (0.3-0.5 mL) intramuscularly into the anterolateral thigh 3, 1, 4
• Children <30 kg: 0.01 mg/kg (up to 0.3 mg maximum) intramuscularly into the anterolateral thigh 3, 1, 4
• Repeat every 5-10 minutes as necessary if symptoms persist or recur 3, 4

Critical positioning and supportive measures:

• Position patient recumbent with lower extremities elevated (if tolerated) to increase venous return 1
• Administer supplemental oxygen as needed 1
• Establish IV access immediately 3

Fluid resuscitation for hypotension or incomplete response to epinephrine:

• Large-volume IV fluid bolus with normal saline or Ringer's lactate: 10-20 mL/kg 3, 1, 2
• Patients with orthostasis, hypotension, or repetitive vomiting require immediate fluid resuscitation 3

Bronchodilators for bronchospasm:

• Albuterol: 4-8 puffs (children) or 8 puffs (adults), or 1.5 mL (children) to 3 mL (adults) via nebulizer 1

Adjunctive Medications (Secondary to Epinephrine)

These should NEVER replace or delay epinephrine in anaphylaxis 2:

• H1 antihistamine (diphenhydramine): 1-2 mg/kg per dose (maximum 50 mg) IV or oral 1, 2
• H2 antihistamine (ranitidine or famotidine): 1-2 mg/kg per dose (maximum 75-150 mg) in combination with H1 antihistamine 2
• Corticosteroids (prednisone): 1 mg/kg (maximum 60-80 mg) orally to prevent biphasic or protracted reactions 2

Mild to Moderate Reactions

For isolated cutaneous symptoms (flushing, urticaria, mild angioedema):

• H1 and H2 antihistamines are appropriate initial treatment 3
• However, continuous monitoring is mandatory to detect progression to anaphylaxis 3
• Administer epinephrine immediately if symptoms progress or worsen 3
• If history of prior severe reaction exists, give epinephrine promptly even for mild symptoms 3

Refractory Anaphylaxis

For patients not responding to initial epinephrine:

• Repeated epinephrine doses 3
• IV fluids, corticosteroids, and vasopressor agents may be needed 3
• Glucagon for patients on beta-blockers: 20-30 μg/kg (children) or 1-5 mg (adults) IV 2
• Prompt transfer to ICU for monitoring is essential 3

Observation Period

All patients receiving epinephrine must be observed 4-6 hours minimum in a medical facility due to risk of biphasic reactions 3, 1. Longer observation may be needed based on:

• Severity of initial reaction 3
• History of biphasic reactions 3
• Delayed symptom onset in previous reactions 3

Discharge Requirements

Before discharge, patients must receive 3, 1:

• Epinephrine auto-injector prescription (2 doses) with hands-on training 3, 1, 2
• Written anaphylaxis emergency action plan 3, 1
• Education on allergen avoidance and early symptom recognition 3, 1
• Medical identification jewelry or wallet card 3
• Continuation of adjunctive medications (H1/H2 antihistamines, corticosteroids) 1
• Referral to allergist for allergen identification and long-term management 2

Critical Pitfalls to Avoid

Common errors that increase mortality:

• Using antihistamines as primary treatment instead of epinephrine for severe reactions 2—antihistamines should never replace epinephrine in anaphylaxis 3
• Delaying epinephrine administration to give other medications 2—fatal reactions are associated with delayed epinephrine 2
• Injecting epinephrine into buttocks, digits, hands, or feet instead of anterolateral thigh 4
• Failing to monitor adequately after symptom resolution 2
• Misdiagnosing angioedema as infection and prescribing antibiotics 2

Special Populations Requiring Caution

While there are no absolute contraindications to epinephrine in anaphylaxis 3, careful consideration is warranted for:

• Patients with cardiovascular disease (myocardial ischemia can occur in untreated anaphylaxis) 3, 1
• Those taking MAO inhibitors, tricyclic antidepressants, or stimulant medications 3, 1
• Patients with recent intracranial surgery, aortic aneurysm, uncontrolled hyperthyroidism, or hypertension 3, 1

The risk of death from anaphylaxis outweighs concerns about epinephrine adverse effects in these patients 3.

High-Risk Patients

Increased risk for severe or fatal reactions 1:

• Adolescents and young adults 1
• History of previous anaphylaxis 1
• Coexisting asthma (especially uncontrolled) 1
• Peanut and tree nut allergies 5
• Underlying cardiovascular disease 5