A sting in the tail? Venom immunotherapy may help or harm: evidence from a new Cochrane review

Key message:Venom immunotherapy is effective in preventing serious allergic reactions and large local reactions to insect stings, but it carries a risk of systemic allergic reaction.

If you’re someone who’s suffered a severe allergic reaction to a sting, or if you’re a clinician with patients who have, you’ll be interested to hear about a new review, from the Cochrane Skin Group, on the use of venom immunotherapy (VIT) for preventing future reactions to stings. As with any treatment, the potential benefits have to be weighed against the risks of harm, and this is a significant issue for this treatment.

VIT, which involves giving the person extracted insect venom, usually through a series of injections, hasn’t previously been evaluated in a high-quality systematic review. The reviewers found seven trials with 392 people to include in the review. The interventions included bee, wasp and ant immunotherapy, given by injection in six trials and under the tongue in one. Results relate to stings given during the trials or occurring accidentally up to four years later.

What did they find?

  • 3/113 (2.7%) participants treated with VIT had a subsequent systemic (whole body) allergic reaction to a sting, compared with 37/93 (39.8%) untreated participants
  • VIT also reduced the risk of large local reactions to stings (20 people reacted out of 60 in the VIT group and 46 out of 51 in the control group)
  • VIT was associated with a significant risk of systemic allergic reaction to treatment, occurring in 9.3% of treated people who had previously had a systemic allergic reaction (reported in one trial as 1 per 25 injections)
  • The two trials assessing quality of life showed a significant improvement in the treatment group after a year compared with the control group, with reduced anxiety and limitation of activities due to fear of insects
  • Effectiveness of VIT for preventing fatal systemic reactions to stings remains unknown (none reported)
  • No evidence that safety or effectiveness differed according to age, route of administration, length of treatment, insect species or dosing schedule

How good is the evidence?

Study quality was mixed and the results come from a small number of studies and participants but evidence for the effectiveness of VIT was consistent across studies. In five studies the people assessing the outcomes were aware of the group to which people had been allocated, which could have influenced their assessment. The follow-up period was short in most studies.

Links:

Boyle RJ, Elremeli M, Hockenhull J, Cherry MG, Bulsara MK, Daniels M, Oude Elberink J. Venom immunotherapy for preventing allergic reactions to insect stings. Cochrane Database of Systematic Reviews 2012, Issue 10. Art. No.: CD008838. DOI: 10.1002/14651858.CD008838.pub2.

Cochrane summary http://summaries.cochrane.org/CD008838/immunotherapy-for-preventing-allergic-reactions-to-insect-stings

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