Allergist Gideon Lack developed a revolutionary hypothesis about food allergies.

Back in the late 1990s and early 2000s, a British researcher named Gideon Lack was feeling a mixture of puzzlement and alarm.

As a pediatric allergist at King’s College London, he’d seen the rate of peanut allergies in the UK double in just 10 years. Meanwhile, more British parents than ever were following the standard medical advice of the time. It boiled down to a simple message: don’t feed your baby peanuts. That way, you’ll avoid the risk of them developing a peanut allergy.

Sounds logical – but apparently it wasn’t working, and no one knew why.

Then something happened. During a trip to Tel Aviv, Lack stumbled upon a pair of facts that led him to a eureka moment. The result would be a hypothesis that turned the conventional wisdom on food allergies on its head.

The key message here is: Allergist Gideon Lack developed a revolutionary hypothesis about food allergies. 

Lack had come to Tel Aviv to give a talk about peanut allergies to a group of Israeli clinicians. At one point during the talk, he asked his audience members for a show of hands: who here has treated at least one case of peanut allergy in the past year?

Whenever he asked this question in the UK, nearly all the hands would go up. But there, in Tel Aviv, only a couple did. Apparently, British children were suffering from peanut allergies at a much higher rate than Israeli children – ten times higher (1.85 versus only 0.17 percent), he later found out.

That was the first fact he stumbled upon. What explained it? Well, that brings us to the second fact.

One day, shortly after his talk, Lack was having lunch with some Israeli friends. One of them was a mother, who was feeding her baby some food. It was a very common baby snack in Israel, his friends informed him. Just out of curiosity, he asked if he could try it for himself.

The snack tasted like peanut butter.

It turned out that Israeli babies were eating food containing peanuts at a much higher rate than British babies – seven times higher (69 versus 10 percent) by the age of nine months old, he later determined.

Could the two facts be connected? Could early exposure to peanuts actually help children to be less likely to develop peanut allergies, rather than the other way around? So, was avoidance a misguided idea? And could the same thing be true of other food allergies as well?

Lack suspected the answer to all of these questions was yes. But it’s one thing to come up with a hypothesis. It’s another to test it, let alone confirm it.

Further research was necessary.