Small doses therapy shows promise for peanut allergy


Giving children and adolescents with peanut allergies small doses of the peanut protein and increasing it over time to build up tolerance could help lessen the severity of their allergic reaction, according to research published in medical journal The Lancet.

In Australia, food allergy affects one in ten infants and one in 100 adults. And peanut allergy is one of the most severe and life-threatening of all.

Senior lecturer in immunology and microbiology at University of Newcastle, Simon Keely explained while many people tend to grow out of milder, more common food allergies as they grow older, the more severe allergies to shellfish and peanut have a tendency to be lifelong.

But the reverse can also happen where people develop food allergy later in life, he added. Unfortunately, no one really knows why people develop or grow out of allergies.

The 99 participants in The Lancet study, who have varying degrees of allergy to peanuts and ranged between seven and 16 years of age, were randomly assigned to either a group that received increasing doses of peanut protein over 26 weeks or a control group that avoided peanuts.

All participants were then given food with increasing amounts of peanut protein (food challenge) under medical supervision to check how much of it lead to an allergic reaction.

In the second part of the trial, the control group was given 26 weeks of oral immunotherapy, followed by the food challenge.

Of the group that was given the peanut protein in the first phase, between 84% and 91% could safely consume roughly the equivalent of five peanuts (800 milligrams of peanut protein) after six months of the treatment (known as oral immunotherapy). This is 25 times the amount of peanut protein they could safely ingest before taking part in the research.

Even more significantly, 62% (24 of the 39 children) of this group could could manage ten peanuts (1,400 milligrams of peanut protein), which is an amount they are unlikely to accidentally encounter in their daily life, compared to the control group.

Allergic reactions were reported by those being given the peanut protein but most of these were mild (oral itching was the most common). One child withdrew from the trial after two doses which led to such severe reactions that adrenaline was required.

“Oral immunotherapy has been proposed and tested for treating patients with allergic asthma and hay fever so it’s not a new concept but getting the balance between administering allergens in such a way that it encourages the patient’s immune response to induce tolerance to that allergen, instead of inducing an allergic reaction is very hard to apply in practice,” said Jay Horvat, immunology lecturer at the University of Newcastle.

The processes involved in creating tolerance to allergens are very complex but can be likened to what happens when you jump into a hot bath, he added. At first your nervous system tells you that the bath is hot by registering a burning sensation as a warning that you may be in danger of scalding, but if you don’t immediately jump out of the bath, your nerves eventually dampen their responses so that you can tolerate sitting in the hot water.

Study leader Dr Andrew Clark from Cambridge University Hospitals in the United Kingdom, told The Lancet the treatment allowed children with all severities of peanut allergy to eat quantities of peanuts, well above the levels found in contaminated snacks and meals, freeing them and their parents from the fear of a potentially life-threatening allergic reaction.

But the research has a number of shortcomings and the therapy is unlikely to be available in the short-term.

One issue is that the participants knew whether they were getting the peanut protein or not in the first part of the trial. This could have affected their reaction in the second part, when all participants were given food with peanut protein.

“This adds possible psychological confounder because people may exaggerate their reaction or underplay it because they want the therapy to work or want to be seen as giving the correct response,” Dr Keely said.

In a linked Comment published at the same time, Matthew J Greenhawt from the University of Michigan Food Allergy Center in the United States, wrote that oral immunotherapy would not be ready for use “until the short-term effects have been comprehensively proven, and the long-term side-effects, mechanism of action, and outcomes are known.”

He pointed out that it was not known whether the therapy produced lasting tolerance, which was of key importance.

Despite these reservations, Dr Horvat noted that this oral immunotherapy trial is extremely promising as it is the first instance of such a therapeutic strategy showing efficacy for the treatment of food allergy, and that this was a major step forward for sufferers of this debilitating disease.

“The main problem is that it doesn’t show how or why it seems to work and that’s the road we would want to go down with food allergies because prevention is better than maintenance,” Dr Keely added.