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Practice Uncertainties Page

Should antihistamines be used to treat anaphylaxis?

BMJ 2009; 339 doi: (Published 10 July 2009) Cite this as: BMJ 2009;339:b2489
  1. D A Andreae, resident, paediatrics1,
  2. M H Andreae, consultant anaesthesiologist 2
  1. 1St Josefskrankenhaus, Freiburg, Germany
  2. 2Vienna Medical University, Vienna
  1. Correspondence to: D A Andreae adriana{at}

    Anaphylaxis is a serious allergic reaction that is rapid in onset and potentially fatal.1 Guidelines and experts agree that adrenaline (epinephrine) is the first line treatment for anaphylaxis.2 Internationally, however, treatment guidelines differ widely,3and the widespread use of antihistamines in anaphylaxis, often as first line treatment instead of adrenaline, has led to concern.4 5

    What is the evidence of uncertainty?

    International guidelines are conflicting on the use of antihistamines in anaphylaxis

    No randomised controlled clinical trials or observational studies exist to inform us: a Cochrane review recently failed to identify any randomised controlled clinical trials evaluating antihistamines in acute anaphylaxis6; only one prospective trial was identified but was excluded as it lacked a control group and did not study patients with anaphylaxis.7 Our own PubMed search also did not identify any randomised controlled clinical trials or observational or cohort studies examining the appropriateness of antihistamines in anaphylaxis.

    Unsurprisingly, a recent comparison of important international guidelines found conflicting advice about antihistamines,3 reflecting the uncertainty in international clinical practice: a US guideline recommends the use of diphenhydramine as second line treatment in anaphylaxis8; evidence for this recommendation is graded as “expert opinion/extrapolated from higher order evidence.”9 An Australian guideline advises against the use of antihistamines in anaphylaxis (except in special circumstances).10 The Resuscitation Council of the United Kingdom still recommends chlorphenamine as second line treatment after initial resuscitation, grading evidence to support its use as …

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