Initial Treatment of Systemic Allergic Reaction

Immediate Management

The American Academy of Allergy, Asthma, and Immunology recommends administering intramuscular epinephrine immediately as first-line treatment for any systemic allergic reaction, even when presenting with only hives and erythema, because these symptoms can rapidly progress to life-threatening anaphylaxis within minutes 1, 2
Inject epinephrine 0.3 mg intramuscularly (IM) in the mid-outer thigh for adults and children ≥25-30 kg, as recommended by the American Academy of Pediatrics 2
Use epinephrine 0.15 mg IM for children weighing 7.5-25 kg, as recommended by the American Academy of Pediatrics 2
Administer epinephrine at the first sign of systemic symptoms after allergen exposure, even if symptoms appear mild, because generalized urticaria can rapidly escalate to respiratory or cardiovascular compromise, according to the American Academy of Pediatrics 2
There are no absolute contraindications to epinephrine use in anaphylaxis—the risk of death from anaphylaxis outweighs concerns about epinephrine adverse effects, as stated by the American Academy of Allergy, Asthma, and Immunology 1

The American Academy of Allergy, Asthma, and Immunology recommends administering diphenhydramine 25-50 mg IV or oral for symptomatic relief of urticaria and pruritus 1
Add ranitidine (H2 antihistamine) twice daily as adjunctive therapy, as recommended by the American Academy of Allergy, Asthma, and Immunology 1
Give systemic corticosteroids (prednisone or methylprednisolone) to potentially prevent biphasic or protracted reactions, though evidence supporting this practice is limited, according to the American Academy of Allergy, Asthma, and Immunology 1

Observe all patients for 4-6 hours minimum after treatment, or longer based on reaction severity, as recommended by the American Academy of Allergy, Asthma, and Immunology 1
Monitor for biphasic reactions, which can occur hours after initial symptom resolution, according to the American Academy of Allergy, Asthma, and Immunology 1

Prescribe epinephrine auto-injector and provide hands-on training before discharge, as recommended by the American Academy of Allergy, Asthma, and Immunology 1
Educate on allergen avoidance and early recognition of anaphylaxis symptoms, according to the American Academy of Allergy, Asthma, and Immunology 1
Provide written anaphylaxis emergency action plan, as recommended by the American Academy of Allergy, Asthma, and Immunology 1
Recommend medical identification jewelry or anaphylaxis wallet card, according to the American Academy of Allergy, Asthma, and Immunology 1