I love a nice clinical trial that answers an important question and one of my favorites from the recent past was the “Learning Early About Peanut allergy” or LEAP trial, published in February of 2015 in the New England Journal.  I probably don’t need to reiterate the results of this truly landmark study, but basically, it upended about two decades worth of advice to parents to avoid exposing their infants to food containing potential allergens, such as peanuts.

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The trial, which enrolled infants at high risk of peanut allergy, found that the rate of peanut allergy at 5 years was 18.8% among those randomized to peanut avoidance, but only 3.6% among those randomized to peanut consumption.  That’s a number needed to treat of around 7 making eating peanut products in the first five years of life about 7 times more efficacious than taking aspirin for an ST-Elevation MI. OK apples and oranges, or peanuts, but still.

But lingering questions remained.  Would these kids be protected in the long-term? Did the study just kick the peanut allergy ball down the field?

To answer the question, the LEAP researchers conducted the LEAP-ON study, in which individuals in the initial study were instructed to avoid all peanut products for 12 months. Without exposure to peanuts, would allergy come roaring back? Would these kids be doomed to eat peanuts three times a week for the rest of their lives?

Well, around 90% of the original trial participants signed on to the no-peanuts-for-12-months pledge. Overall, adherence was OK. As you might expect, those who had originally been randomized to avoid peanuts had an easier time staying off the sauce – 80% of them reported complete peanut avoidance. Only 40% of those who had been randomized to eat peanuts originally were able to stay away for the year. No shame there, peanuts are delicious.

Bottom line, after 12 months of avoidance there were 6 new cases of peanut allergy, but three from each group. In other words, you didn’t see a “rebound” in peanut allergy among those kids initially randomized to eating peanuts.  By the end of this study, 18.6% of those who had initially avoided peanuts and 5% of those who had eaten peanuts from a young age had confirmed allergy.

The point here is that the protection from allergy conferred from early exposure to peanuts persisted even through a year of not eating peanuts. This is a very good thing for the rare kid out there who doesn’t like peanuts – it seems like the protection you gained in infancy will stick around.

Now, I should mention that there was no control group here. I’m curious what might have happened to kids instructed to keep right on eating lots of peanuts. We also don’t know if avoidance for more than a year might let allergy recrudesce.

But taking this study with the results of the original trial, it’s not exactly a leap to say that early exposure to peanuts might dramatically curb the rising tide of peanut allergy in the developed world.