Injecting small amounts of pollen-extract just below the skin in people who have hayfever can desensitize them to the pollen and reduce their symptoms. It also reduces the amount of medication they use.
These are the conclusions from a Cochrane Review of this therapy. The review pooled data from 51 trials involving a total of 2871 patients, 1645 of whom received an active treatment, while 1226 received an inactive placebo. Treatment consisted of an average of 18 injections spread over a range of times from three days to three years.
The review found that the treatment was safe, with serious adverse reactions to the therapy occurring in only four patients; one of whom had been given a placebo. Three had an anaphylactic reaction and one had an attack of asthma. All of them recovered fully and none dropped out of the trial as a result of these side-effects.
“Because of the very low, but real, risk of an adverse reaction, this treatment should only given in facilities that have full resuscitation back up. Unfortunately, in the UK, this means that it can only be given in specialized centres, which greatly limits its use,” says Review Authors Moises Calderon, a Senior Clinical Fellow in the Department of Allergy and Respiratory Medicine at the Royal Brompton Hospital, London, and Professor Aziz Sheikh, Primary Care Research and Development at the University of Edinburgh.
The risk of an adverse reaction also means that it should not be given to people who also have asthma.
The Cochrane Review concluded that injection immunotherapy is a safe and valid treatment for patients with hayfever, and particularly those who have not responded to other treatments.