Feeding small amounts of peanuts to children to cure them of their allergy increases the risk of them suffering a dangerous anaphylactic shock by three-fold in the year after treatment, a major review has found.

Around 1.1 million people in Britain suffer from peanut allergy, including 250,000 children, and recent studies suggested they could be desensitised by increasing exposure over time to prime the immune system.

But a review of 12 studies involving more than 1,000 youngsters aged nine to 12 found that in the year after treatment those who had tried immunity treatments saw a large increase in anaphylaxis and other allergic reactions.

While 7.7 per cent of children who simply avoided peanuts suffered anaphylactic shock in the follow up period, nearly one in four of those who had therapy had an attack. They were also twice as likely to need to use an epi-pen during the period, and to suffer serious adverse events.