When should I use epinephrine instead of an antihistamine?

The World Allergy Organization's guidance says intramuscular epinephrine is the first-line treatment in anaphylaxis. Food Allergy Canada says antihistamines and asthma medications shouldn't be used instead of epinephrine, and that an auto-injector should be used before them. Antihistamines can be given afterwards, mostly for comfort with itching and hives.

Getting the order right matters. A study of 483 food-induced anaphylaxis cases at nine Canadian emergency departments found 53% of patients were given antihistamines, while only 41% of those carrying an auto-injector used it before reaching hospital. A 2026 review presented at the CSACI meeting found antihistamines and steroids reported in 22 of 26 anaphylaxis studies worldwide, sometimes more often than epinephrine.

Your anaphylaxis emergency plan lists the signs that mean "give epinephrine now". Use it, call 911, and don't delay. More in epinephrine or antihistamine first?