Australasian Society of Clinical Immunology and Allergy

Don’t use antihistamines to treat anaphylaxis – prompt administration of adrenaline (epinephrine) is the only treatment for anaphylaxis.

For emergency treatment of a severe allergic reaction (anaphylaxis) it is important to promptly administeradrenaline (epinephrine) by intramuscular injection using an adrenaline autoinjector if available, or by using adrenaline ampoules and syringe (the latter is only suitable in a medical setting). There is a high risk of potential harm (disability or death) from anaphylaxis if it is not treated promptly with adrenaline. There are also cost implications from delayed or inappropriate treatment of anaphylaxis, such as additional ambulance, emergency department and hospital costs, as well as additional anxiety for patients and their families or carers. Antihistamines are recommended for treatment of mild and moderate allergic reactions, including allergic rhinitis (hay fever), but have no role in treating or preventing respiratory and cardiovascular symptoms of anaphylaxis. In particular, oral sedating antihistamines should never be used in patients with anaphylaxis as side effects (drowsiness or lethargy) may mimic some signs of anaphylaxis. Injectable promethazine should not be used in anaphylaxis as it can worsen hypotension and cause muscle necrosis.

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Supporting evidence
  • Sheikh et al, ‘H1-antihistamines for the treatment of anaphylaxis: Cochrane systematic review’, Allergy. 2007 Aug;62(8):830-7.
  • Cox et al, ‘Allergen immunotherapy: a practice parameter third update’, J Allergy Clin Immunol. 2011 Jan;127(1 Suppl):s1–55.
  • Lieberman et al, ‘The diagnosis and management of anaphylaxis practice parameter 2010 update’, J Allergy Clin Immunol. 2010 Sep;126(3):477-80.e1–42.
  • Andreae, D. and M. Andreae, ‘Should Antihistamines be Used to Treat Anaphylaxis?’, BMJ. 2009;338:b2489.