Slide 1: Histamine receptor 1 blockers are often used as adjunctive therapies, alongside epinephrine, in the treatment of anaphylaxis. However, they have not actually been shown to reduce the incidence of shock in this population. What symmptom of anaphylaxis do H1 blockers help with? A) Wheezing. B) Urticaria. C) Nausea and vomiting. D) None of the above.

Slide 2: B) Urticaria. Epinephrine is the only drug with solid evidence showing its value in reducing the life threatening complications of anaphylaxis. No RCT data exists to support the use of antihistamines, but these agents are often used because histamine receptors exist on mast cells, the primary mediators of anaphylaxis. They appear to help with skin symptoms more than anything else.

Slide 3: Bonus! Epinephrine treats the downstream effects of histamine receptor activation (beta adrenergic activity, i.e. blooc pressure rise and bronchospasm). On the other hand, histamine receptor blockers are only effective prior to histamine binding to its receptor.


  • Winbery SL, Lieberman PL. Histamine and antihistamines in anaphylaxis. Clin Allergy Immunol. 2002;17:287-317.
    PMID 12113221

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