Peanut allergy can be made worse by desensitising approach, study suggests

Treating childhood peanut allergy by gradually increasing tolerance may make the condition worse instead of better, a new study suggests.

“Food challenge” studies have indicated that oral immunotherapy, which involves gradually raising doses of an allergen over time, can be effective.

However, new research raises doubts about this approach. It shows that compared with avoiding peanuts, attempts to desensitise children in the “real world” promote allergic reactions, including the serious and potentially fatal condition anaphylaxis.

Scientists pooled the results of 12 trials involving more than 1,000 young patients with an average age of nine whose progress was followed for a year.

The studies compared the effectiveness of oral immunotherapy and avoidance using different peanut products and doses.

Researchers found that peanut oral immunotherapy tripled rates of anaphylaxis, from around 7.1% to 22.2%.

Allergic reactions leading to vomiting, abdominal pain, mouth itching, hives, wheezing and asthma all increased.

The findings favour avoidance over current forms of oral immunotherapy, said the study authors writing in The Lancet medical journal.

Lead researcher Dr Derek Chu, from McMaster University in Canada, said: “Numerous studies of varying quality have been published on oral immunotherapy, but its effectiveness and reliability remains unclear.

“Our study synthesises all randomised clinical trials comparing peanut oral immunotherapy to no immunotherapy in order to generate the highest quality evidence to inform decision-making.

“It shows that current peanut oral immunotherapy regimens can achieve the immunological goal of desensitisation, but that this outcome does not translate into achieving the clinical and patient-desired aim of less allergic reactions and anaphylaxis over time.

“Instead, the opposite outcome occurs, with more allergic and adverse reactions with oral immunotherapy compared with avoidance or placebo.”

He added: “Our results do not denounce current research in oral immunotherapy, but the method needs to be more carefully considered, improvements in safety made and measures of success need to be aligned with patients’ wishes.”

More than six million people are affected by food allergies in Europe and North America, including 8% of children and 2%-3% of adults, said the scientists.

While common allergies to milk and egg are often out-grown by the age of five to 10, peanut allergy can be a lifelong problem.

Studies of oral immunotherapy measure treatment success by whether a patient can pass a supervised food challenge.

However, this cannot predict a patient’s future risk in the real world, the researcher pointed out.

Commenting in the journal, Dr Graham Roberts, from the University of Southampton, said it would be useful to compare oral (by mouth) and epicutaneous (skin exposure) immunotherapy.

He added: “Although epicutaneous immunotherapy is less effective, it has a better safety profile than oral immunotherapy, which some patients might find more acceptable.

“Finally, we should not forget that we now know that the early introduction of peanut products into the infant diet can prevent most cases of peanut allergy. Moving forward we need to develop implementation strategies to reduce number of patients with peanut allergy.”