20 Feb Can the cure for peanut allergies be… peanuts?

A large clinical trial published recently in the Lancet confirms what smaller studies have shown in the past: Oral immunotherapy – swallowing tiny, increasing amounts of peanut over time – has the ability to desensitise allergic individuals to peanuts.

“May contain nuts” appears so often in the ingredients lists of processed foods that it might seem to most people to have the warning value of the boy who cried “wolf” in Aesop’s fable. Allergy to nuts, particularly to peanuts (strictly legumes, not nuts), is not, however, to be treated lightly. The anaphylactic shock provoked is always nasty and can, if the swelling obstructs someone’s airways, kill.

Peanuts are one of the leading causes of food allergy reaction, and 400,000 school-aged children in the US have this allergy, according to the American College of Allergy, Asthma and Immunology. Symptoms may occur from any contact with the peanut protein, which is why cross-contamination of foods can be very dangerous.

Youngsters who have peanut allergy, and their parents, may therefore be interested in a study by Andrew Clark and Pamela Ewan of Cambridge University Hospitals, which is reported in the Lancet. This suggests that the immune system (whose adverse reaction causes anaphylaxis) can be trained to become less sensitive to peanuts, to the point where accidental exposure to small amounts of them will cause no harm.

The two researchers made this discovery by recruiting 100 peanut-sensitive youngsters aged between seven and 16 and asking half of them to eat increasing amounts of peanut protein daily, up to 800mg (roughly equivalent to five peanuts) for 26 weeks, and the other half to continue avoiding foods containing them for the same period. That done, they were tested to see how much peanut protein they could tolerate. Those in the second group were then asked to behave as the first group had done for another 26 weeks, and tested again.

In the first group, 84% of participants could eventually tolerate nibbling the equivalent of five peanuts a day. No member of the control group could do likewise until after receiving similar treatment, when 91% could. In addition, 62% of the first group were unaffected by ingesting a single 1,400mg dose of peanut protein — a large amount, unlikely to be scoffed by accident. And 54% of the second group were able to do so once they, too, had undergone the experimental regimen.

This is not, the researchers emphasise, an experiment that anyone should attempt at home. Even under medical supervision adverse reactions occurred. Most were mild, but one person had to be treated twice with adrenalin—and, not surprisingly, then withdrew from the study.

The new results are a “very positive finding” because peanut-allergic people who become able to tolerate peanuts don’t have to worry about any accidental exposure or trace amounts of contamination, said Dr Anna Nowak-Wegrzyn, associate professor of pediatrics at Mount Sinai Hospital in New York, who was not involved in the study.

Still, this is not a cure, she noted. The current thinking is that people who undergo oral immunotherapy need to continue eating peanuts every day in order to maintain tolerance.

Further research is needed to confirm the new results in more patients, and to see just how long the peanut allergy protection lasts, she said.

Journal Reference:

Assessing the efficacy of oral immunotherapy for the desensitisation of peanut allergy in children (STOP II): a phase 2 randomised controlled trial