Epinephrine is the only treatment that prevents death in anaphylaxis
Intramuscular epinephrine rapidly reverses airway edema and shock.1 Current evidence does not support use of antihistamines and corticosteroids to prevent progression of anaphylaxis or biphasic reactions, and their use should not delay epinephrine administration.2
Second-generation antihistamines are preferred over first-generation antihistamines as adjunctive therapy
Second-generation H1-antihistamines, such as cetirizine, are better tolerated and less sedating than diphenhydramine.3 Dissolvable oral formulations are available in Canada and are helpful when swallowing is difficult. If parenteral administration is needed, diphenhydramine is the only injectable antihistamine option.
Intranasally delivered epinephrine could benefit those with needle phobia or other limitations
Intranasal epinephrine is approved in the United States but, as of November 2025, intranasal epinephrine remains under review in Canada for approval as a needle-free option for patients aged 4 years and older and weighing at least 15 kg.4 An intranasal spray device delivers 2 mg of epinephrine into 1 nostril. Until intranasal epinephrine is available in Canada, intramuscular epinephrine autoinjectors remain the standard of care. Clinicians should prescribe them, provide training, and stress their immediate use at the first signs of anaphylaxis.
Recommendations for emergency medical services (EMS) after epinephrine use vary
A 2023 practice parameter update on anaphylaxis advises that home observation may be reasonable if symptoms resolve completely within 10 to 15 minutes after a single epinephrine dose, provided the patient has immediate access to a second dose and to emergency medical care.2 In contrast, 2018 guidance from the Canadian Paediatric Society recommends that all children treated with epinephrine be assessed in an emergency department.5
Epinephrine autoinjector prescribing should be individualized
Autoinjectors are recommended for all patients with first-time or prior anaphylaxis. People with less severe allergic reactions, those with risk factors for anaphylaxis (e.g., mast cell disorders, uncontrolled asthma), and those who are located more than 30 minutes away from EMS response or transport to hospital should also be prescribed self-injectable epinephrine. Pediatric patients should have an allergist referral.5 For patients with mild or uncertain reactions, prescription of epinephrine after anaphylaxis should be guided by shared decision-making.2
Footnotes
Competing interests: Samira Jeimy has been an advisory board member with Sanofi Genzyme, GSK, and ALK; received honoraria for speaking engagements from GSK and L’Oréal; and provided consultancy services for Canadian Agency for Drugs and Technologies in Health. Dr. Jeimy is a chair of the Women in Allergy and Immunology committee, sits on the board of directors with the Canadian Society of Allergy and Clinical Immunology (CSACI), and is chair of the Women in Medicine committee and vice-chair of the Allergy and Immunology committee with the Ontario Medical Association. Elissa Abrams is president of the allergy section of the Canadian Paediatric Society and a board member with CSACI. No other competing interests were declared.
This article has been peer reviewed.
Disclaimer: Elissa Abrams is an employee of Public Health Agency of Canada (PHAC); views expressed are her own and not those of PHAC.
References
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