Why one study could change how doctors treat peanut allergies

WATCH ABOVE: Dr. Samir Gupta explains what you need to know about the new peanut allergy study. 

More On Call with Dr. Samir Gupta stories on Globalnews.ca

TORONTO –  A recent study suggests exposing high-risk children to peanuts earlier in life could lower the risk of them later developing a peanut allergy.

The Learning Early About Peanut Allergy (LEAP) study, published in the New England Journal of Medicine, gave a skin prick test to 640 infants aged between 4 and 11 months, who were thought to be at high risk of developing a peanut allergy.

The test looked for peanut sensitivity, and children with a negative or moderately positive skin prick result were included in the study. The children were then randomly assigned to either receive a minimum of six grams of peanuts per week (divided in a minimum of three meals per week) up to the age of five, or to avoid peanuts altogether.

The results were impressive.  In the negative skin prick test group, only 1.9 per cent of the kids who consumed peanuts had evidence of a peanut allergy at age five, compared to 13.7 per cent of the kids who avoided peanuts.

In the positive skin prick test group, 10.6 per cent of the kids who consumed peanuts had evidence of a peanut allergy at age five, compared to 35.3 per cent of the kids who avoided peanuts. All of these results were statistically significant, and there were no differences in major side effects between groups.

READ MORE: Want to avoid allergies in your kids? Try turning off your dishwasher

The LEAP study is an instance where a well-designed scientific study really addresses a question that we didn’t know the answer to.   Medical guidelines as recently as 2000 actually recommended the opposite – avoiding allergenic foods like peanuts in infants at high risk for allergy.  But the problem was that this “primary prevention” approach didn’t seem to work.

Studies showed that these kids still eventually developed the allergies, as was demonstrated in a review by D. deSilva and colleagues in Allergy in 2014.  At the same time, the prevalence of peanut allergy in the western world increased dramatically.  So by 2008, the recommendation for avoidance was withdrawn, and  around that time, several observational studies, particularly a study by G. Toit and colleagues in the Journal of Allergy and Clinical Immunology in 2008, came out suggesting that kids who had been exposed to allergenic foods at a young age seemed to have a lower chance of these allergies later in life.

WATCH: A new study suggests many peanut allergies can be prevented. Researchers say their findings could lead to major changes in food allergy guidelines. Mark McAllister reports.

So we started wondering whether doing just the opposite – actually exposing kids to the allergen was a better idea.  And the LEAP study is the first trial to actually prove that concept.

But practically speaking, does this mean that we can now recommend this approach, based on a single study?  We are always loathe to change practice based on a single study.  That being said, let’s evaluate the study itself.

It’s a randomized-controlled trial, which is the highest quality of evidence that we have. There was no placebo but that is very unlikely to have created bias. The study was carried out very well, the effect size was large, there were no major safety concerns, findings were consistent in both kids who had no peanut sensitivity on skin testing and those who had mild sensitivity, and importantly, findings were consistent with the recent observational data that we have.

READ MORE: City kids more likely to have food allergies: study

I have no concerns about the quality of the study.  Which leads to the next issue, which is whether the results are actually applicable to our population.  The study was done in the UK, the dietary source of peanut was similar to what we could find here, the tests done at study entry are available here, and although the population was over 70 per cent white, the results were largely similar when they looked at individual racial subgroups.

Doctors definitely like to see results replicated before we change practice based on a single study. But to my mind, this is one of those circumstances where because we really don’t know what to do regarding allergy prevention, and because of the size of the effect and the severe consequences of peanut allergies, our new guidelines will likely change based on this study, and this will become the recommended approach.

Here are five things you need to know about the LEAP Study:

This is a study of prevention – not treatment. 

The study shows that kids who are at risk of a peanut allergy may be prevented from developing the allergy if they consume peanuts.  Kids who already had established peanut allergy were not given peanuts in the study – so it’s not a treatment for established peanut allergy.

The results are only relevant for kids at high risk of severe peanut allergy. 

That means kids four to 11 months old that have severe eczema, egg allergy, or both.  What we do with kids with only mild eczema remains unclear.

Your child will need a skin test and an oral challenge.

If your child meets these criteria, they still need a skin test to see if they’re sensitive to peanuts. If they have a strong reaction on the skin test (which was nine per cent of kids in this study), giving peanuts was not considered safe.  Also they need a food challenge to make sure they don’t already have a peanut allergy, in which case the protocol also wasn’t considered safe.

What happens if your child stops eating peanuts?

Kids had peanuts at least three times per week until age five.  That’s a lot of peanut consumption, for a long time.  And the challenge is that we don’t know if a smaller dose or shorter duration would suffice, and whether stopping the consumption will then lead to the allergy coming back.  There is another study underway to look at that.

What about other allergies?

It’s unclear if results of the LEAP study can be applied to other foods, such as milk, eggs, and tree nuts.  But it teaches us a lot about the concept of immune tolerance, and that may very likely extend to other foods.  There was a small study by DJ Palmer and colleagues published in Clinical Immunology in 2013 that showed promise for eggs, and other foods will likely be studied now.

Follow @SammyG_MD