No, eating small amounts of peanuts will not cure an allergy, review suggests

Contrary to what you might have heard, eating tiny amounts of peanuts does not appear to help a child with a peanut allergy build up a tolerance in the real world. 

In fact — according to a recent review by researchers in Canada, the U.S. and Italy — while attempts at "oral immunotherapy" work in the clinic, they might make things worse, leading to more life-threatening allergic reactions. 

"The risk or the chance of having a reaction is much higher, two to three higher on [oral] immunotherapy," said Dr. Derek Chu, a doctor and fellow in clinical immunology and allergy at McMaster University in Hamilton, who led the meta-analysis, which was published in Thursday's issue of the medical journal The Lancet.

The idea behind oral immunotherapy, which is still experimental, is that children and adults with allergies might build up tolerance to peanut protein by eating tiny amounts under medical supervision — working up to about a full peanut over months.

The goal is to improve an allergy patient's quality of life and to cut the risk of developing an allergic reaction if the wrong food is accidentally eaten.

But babies who haven't developed a food allergy are in a different category than children and adults. For feeding babies, the advice to introduce peanut products into the infant diet to prevent cases of peanut allergy still stands, pediatricians stressed.

"We now know that we can prevent it in so many of these children, [and for] 85 per cent of these children we can prevent it by giving it early. Now we're looking at can we treat the kids that we missed?" said Dr. Douglas Mack, a pediatric allergist who was not involved in the research. 

Chu's team reviewed the results of 12 randomized, controlled trials on more than 1,000 people with peanut allergies who either used oral immunotherapy, no immunotherapy or a placebo.

No patient died in any of the trials. That doesn't mean it can't happen- Dr. Derek Chu, McMaster University

Patients started off eating one thousandth of a peanut. Participants were age nine on average (between 5 and 12 years), and there were some adults.

The review findings showed patients could tolerate limited amounts of peanut while in the clinic, but the protection wasn't complete, Chu said. Factors as simple as having a cold or exercising within a few hours of receiving a dose of peanut could break the tolerance that's been built up at the clinic. 

The reactions ranged from mild, such as vomiting, all the way up to severe, anaphylactic reactions needing treatment with epinephrine.

"No patient died in any of the trials. That doesn't mean it can't happen. Conversely, no patient had a cure," said Chu, who has a peanut allergy himself. 

"We're not outright saying that this should be denounced or that this should be abandoned. Far from it," Chu said. "From a research standpoint this is a major advance. We're almost there. We can make it in the clinic but now we just need to make that next step to also make it work outside the clinic."

'Lots of adverse effects'

As a pediatrician, Dr. Graham Roberts of the University of Southampton, U.K. treats and studies childhood allergy. He wrote a journal commentary accompanying the meta-analysis, which he called well done. His main criticism was that the study data didn't include patients' views about the impact of the therapy, such as on their quality of life.

With medical therapies, effectiveness needs to be traded off with adverse effects, Roberts said. He suggested peanut immunotherapy using skin patches instead of orally might be a safer option.

"Oral immunotherapy and skin-based immunotherapy are very different in this respect," Roberts said in an email to CBC News. "Oral immunotherapy is very effective but causes lots of adverse effects, whereas skin-based immunotherapy is not as effective but has fewer side-effects. Different patients may prefer different approaches."

The skin-based "peanut patch" is not approved for clinical use in Canada.

The researchers estimated that peanut oral immunotherapy was associated with 151 more episodes of anaphylaxis per 1,000 patients. In comparison, historically there were about 71 episodes.

Janet Glendenning's daughter, Chloe, is two years old and is allergic to nuts and sesame. She's receiving oral immunotherapy in Burlington, Ont. 

Chloe's allergy limits the Barrie, Ont., family's visits to restaurants and other people's houses. 

"I was very worried, and it affected every part of our life," said Glendenning, adding she realizes it isn't a cure. "Not having to worry is a huge reason why we're doing this treatment."

Chloe is a patient of Dr. Mack's, who is also an assistant clinical professor at McMaster. He agrees with the need for more research but also sees how oral immunotherapy is helping some kids.

"I hope it doesn't scare families off from doing it," Mack said. "But I hope it makes them kind of really consider whether this is for them."

Oral immunotherapy is also not publicly covered. Mack's clinic offers it for about $7,000.

Medical researchers are still investigating how different age groups of children respond to immunotherapy. 

A previous Canadian study by Dr. Edmond Chan suggested that oral immunotherapy is safe in preschoolers, based on a look at one- to five-year-old children. The researchers found one of 270 children who received oral immunotherapy had a "severe" reaction. 

Overall, oral immunotherapy is about 80 per cent effective for short-term desensitization to accidental exposures in children under age six, said Chan, head of allergy and immunology at BC Children's Hospital. After age six, it falls to about 60 to 80 per cent.

Complete avoidance and carrying an epinephrine auto-injector remains a mainstay for people with peanut allergy. 

Allergies to peanut are life-long in 80 to 85 per cent of cases and affect two per cent of children and one per cent of adults in high-income countries, according to previous studies.