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Rachel Feltman: For Scientific American’s Science Quickly, I’m Rachel Feltman.

An estimated one out of every 10 people in the U.S. has some kind of food allergy, which adds up to more than 33 million Americans. Peanut allergies are among the most common and certainly take the lead as the most visible.

But peanut allergies weren’t always so prevalent. In the late 1990s, a nationwide survey found that peanut allergies were reported in 0.4 percent of American children. Just over a decade later, that number had more than tripled.

Scientists still aren’t completely sure what led to this big uptick, but it could stem in part from parental anxiety over peanut allergies—and misguided advice about how to keep kids safe.

Here to tell us more about the latest research on peanut allergies, including new avenues for treatment and prevention, is Maryn McKenna, the author of a recent article on the subject for Scientific American. Maryn is a journalist who covers food policy and public health.

Thank you so much for coming on to chat with us today.

Maryn McKenna: Thanks for having me.

Feltman: So what do we know about the origins of peanut allergies?

McKenna: This is a really interesting mystery still. No matter how much study and how much research funding has gone into the problem of peanut allergy—and food allergies more broadly—a lot of it still remains kind of opaque.

Feltman: Mm.

McKenna: We know the biological mechanisms of what makes an allergy happen, but why peanut allergy in particular came on the scene 20, 30 years ago or so, and why it blew up to such a major public health problem—people are still working that out.

Feltman: So I guess let’s start with the easier question, then, which is: What is a food allergy? How does it work, both genetically and in the moment in a person’s body?

McKenna: I think most people are familiar with the concept of our having an immune system that, through a variety of mechanisms, defends our bodies against the outside world, broadly speaking, against things that are not us. Most of the time, the immune system works really well to adapt its reactions, its defenses of us, to the way we continue to live our lives.

Sometimes its reactions get wildly out of scale, and that’s what happens in food allergy and peanut allergy. The immune system recognizes proteins in these foods as being sort of not self, not part of us, and mounts an extraordinary reaction that expresses itself in the kind of symptoms that, if you’re allergic, you’ve experienced or that you may be familiar with from hearing about them from other people: hives, itchiness, difficulty breathing, difficulty swallowing; in the worst presentations depressed blood pressure, inability to breathe and sometimes, in, in the worst case, a heart attack.

Feltman: And what are the actual rates of nut allergy? It’s definitely one of the ones we hear about a lot, but how prevalent is it?

McKenna: This can be a frustrating question to try to answer because what we know about people being allergic depends on their telling researchers that they’re allergic …

Feltman: Mm.

McKenna: So it’s all self-reported. There are biological markers for allergy, but we don’t apply tests for those biological markers to the entire population, so all of the data relies on people telling researchers who have asked that an allergy is present in themselves or in their kids, if they’re parents answering for children.

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