Excerpted from “Blind Spots: When Medicine Gets It Wrong, and What It Means for Our Health” by Marty Makary, M.P.H. ’98. Used with the permission of the publisher, Bloomsbury.

“Hi, my name is Chase, and I’ll be your waiter. Does anyone at the table have a nut allergy?”

My two Johns Hopkins students from Africa, Asonganyi Aminkeng and Faith Magwenzi, looked at each other, perplexed.

“What is it with the peanut allergies here?” Asonganyi asked me. “Ever since I landed at JFK from Cameroon, I noticed a food apartheid — food packages either read ‘Contains Tree Nuts’ or ‘Contains No Tree Nuts.’ ”

Asonganyi told me that even on his connecting flight to Baltimore, the flight attendant had made an announcement: “We have someone on the plane with a peanut allergy, so please try not to eat peanuts.” And on his first day at Johns Hopkins, a classmate invited him to dinner. The invite went something like this: 1) Would you like to come over for dinner; and 2) Do you have a peanut or other allergy?

“What’s going on here?” Asonganyi asked with a big smile. “We have no peanut allergies in Africa.”

Faith, who had flown in from Zimbabwe, nodded in agreement.

I looked at them and smiled. “In Egypt, where my family is from, we don’t have peanut allergies either,” I said. “Welcome to America. Peanut allergies are real and can be life-threatening here.”

Their observation reminded me of when my friend’s school banned peanuts from the campus. School administrators actually inquired with security authorities if metal detectors could detect a peanut. And then one day there was an “emergency.” A peanut was found on the floor of a school bus. It was like discovering an IED in Iraq. The kids were ordered to quietly exit the bus single-file until someone arrived to “decontaminate” the bus. Luckily, the peanut did not detonate and harm the public.

How did we get here?

In 1999, researchers at Mount Sinai Hospital estimated the incidence of peanut allergies in children to be 0.6 percent. Most were mild. Then starting in the year 2000, the prevalence began to surge. Doctors began to notice that more and more children affected had severe allergies.

The 1990s was the decade of peanut allergy panic. The media covered children who died of a peanut allergy, and doctors began writing more about the issue, speculating on the growing rate of the problem. The American Academy of Pediatrics (AAP) wanted to respond by telling parents what they should do to protect their kids. There was just one problem: They didn’t know what precautions, if any, parents should take.

Rather than admit that, in the year 2000 the AAP issued a recommendation for children zero to three years old and pregnant and lactating mothers to avoid all peanuts if any child was considered to be at high risk for developing an allergy.

The AAP committee mimicked what the UK health department had recommended two years earlier: total peanut abstinence. The recommendation was technically for high-risk children, but the AAP authors acknowledged that, “The ability to determine which infants are high risk is imperfect.” Having a family member with any allergy or asthma could qualify as “high-risk” using the strictest interpretation. And many well-meaning pediatricians and parents read the recommendation and thought, Why take chances? Instantly, pediatricians adopted a simple mnemonic to teach parents in their offices: “Remember 1-2-3. Age 1: start milk. Age 2: start eggs. Age 3: start peanuts.” A generation of pediatricians was indoctrinated with this mantra.

I did a close read of that 1998 UK health department recommendation to see if it cited any scientific study to back up the decree. I found one sentence stating that moms who eat peanuts are more likely to have children with peanut allergies. In other words, it blamed the moms. The report cited a 1996 British Medical Journal (BMJ) study. So I pulled that up and took a close look.

I couldn’t believe it.

The actual data did not find an association between pregnant moms eating peanuts and a child’s peanut allergy. But that didn’t matter: The train had left the station.

How could “experts” make a recommendation citing a study that did not even support the recommendation?

Bewildered by how the study seemed so badly misconstrued, I called its lead author, Dr. Jonathan Hourihane, a professor of pediatrics in Dublin. He shared the same frustration and told me he had opposed the peanut avoidance guideline when it came out. “It’s ridiculous,” he told me. “It’s not what I wanted people to believe.”

I specifically asked him how he felt about his study being used as the source to justify the sweeping recommendation. “I felt crossed,” he responded, using a little UK slang for feeling betrayed. He had not been consulted on the national guideline.

The 2000 AAP guideline was published in the specialty’s top journal, Pediatrics, activating many pediatricians to evangelize mothers when they brought their babies in for a checkup. Doctors and public health leaders had their new marching orders. Within months, a mass public education crusade was in full swing, and mothers, doing what they thought was best for their children, responded by following the instructions to protect their children.

But despite these efforts, things got worse. By 2004, it was clear that the rate of peanut allergies was going the wrong way. Peanut allergies soared. More concerning, extreme peanut allergies, which can be life-threatening, became commonplace in America.

Suddenly, emergency department visits for peanut anaphylaxis — a life-threatening allergic swelling of the airways — skyrocketed, and schools began enacting peanut bans. By 2007, 18 percent of Virginia schools had banned peanuts altogether. And in 2016, the Parkway School District in Missouri, reported 957 students with documented life-threatening food allergies, most of which were to peanuts. The rate had increased 50 percent from just six years prior, and more than 1,000 percent from a prior generation.

As things got worse, many public health leaders doubled down. If only every parent would comply with the pediatrics association guideline, they thought, we as a country could finally beat down peanut allergies and win the war. The dogma became a self-licking ice cream cone.

But the groupthink could not have been more wrong.

Swimming against the current

Stephen Combs is a salt-of-the-earth pediatrician in rural East Tennessee. At one point, the other pediatricians in Combs’s group noticed something unique about his patients. None of them had peanut allergies. This despite the fact that his colleagues were seeing more and more kids with peanut allergies in their practices. What was going on?

I was curious to learn more about his impressive track record, so I traveled to the beautiful rolling hills of Johnson City, Tennessee, to visit him. (I often learn a lot when I get outside of the bubble of my urban university hospital.)

I discovered that all the pediatricians in Combs’s group were as impressive as he was: making house calls, staying late to see patients, and educating parents on how to raise healthy children. They all practiced pediatrics the same way.

Except for one thing.

Combs had never followed the AAP guideline for young children to avoid peanuts. The reason for his defiance was simple. Combs did his residency at Duke Medical Center in North Carolina, where he trained under world-famous pediatric immunologist Rebecca Buckley. When the AAP guideline came out in 2000 with a big splash, Buckley recognized that it violated a basic principle of immunology known as immune tolerance: the body’s natural way of accepting foreign molecules present early in life. It was like the dirt theory, whereby newborns exposed to dirt, dander, and germs may then have lower allergy and asthma risks. Buckley confidently told her students and residents, including Combs, to ignore the AAP recommendation, and in fact, to do the opposite. She explained that peanut abstinence doesn’t prevent peanut allergies, it causes them.

Her explanation turned out to be prophetic.

Since his training with Buckley, Combs has consistently instructed parents to introduce a touch of peanut butter (mixed with water to avoid a choking risk) as soon as a child is able to eat it. To this day, the thousands of children in East Tennessee lucky enough to have Combs as their pediatrician do not have peanut allergies.

Extrapolating the principle to other potential allergens, Combs also encouraged the early introduction of eggs, milk, strawberries, and even early exposure to dogs and cats. As a result, the children in his practice rarely developed an allergy to these things, and when they did, it was mild.

An embarrassingly simple study

Buckley and her trainees were not alone in bucking the AAP’s guidance. In fact, many experts in immunology had long known of mouse studies showing that avoiding certain foods triggers allergies to those foods. But the laboratory immunology community was largely disconnected from the clinical allergist and the pediatric community.

Gideon Lack, a pediatric allergist and immunologist in London, challenged the UK guideline. It “was not evidence-based,” he wrote in The Lancet in 1998. “Public-health measures may have unintended effects … they could increase the prevalence of peanut allergy.”

Two years later, the same year the AAP issued their peanut avoidance recommendation, he was giving a lecture in Israel on allergies and asked the roughly 200 pediatricians in the audience, “How many of you are seeing kids with a peanut allergy?”

Only two or three raised their hands. Back in London, nearly every pediatrician had raised their hand to the same question.

Startled by the discrepancy, he had a Eureka moment. Many Israeli infants are fed a peanut-based food called Bamba. To him, it was no coincidence.

Lack quickly assembled researchers in Tel Aviv and Jerusalem to launch a formal study. They found that Jewish children in Israel had one-tenth the rate of peanut allergies compared to Jewish children in the UK, suggesting it was not a genetic predisposition, as the medical establishment had assumed. Lack and his Israeli colleagues titled their publication “Early Consumption of Peanuts in Infancy Is Associated with a Low Prevalence of Peanut Allergy.”

However, their publication in 2008 was not enough to uproot the groupthink. Avoiding peanuts had been the correct answer on medical school tests and board exams, which were written and administered by the American Board of Pediatrics. Many in the medical community dismissed Lack’s findings and continued to insist that young children avoid peanuts. For nearly a decade after AAP’s peanut avoidance recommendation, neither the National Institutes of Health’s (NIH’s) National Institute of Allergy and Infectious Diseases (NIAID) nor other institutions would fund a robust study to evaluate the recommendation, to see if it was helping or hurting children.

But things were getting worse. The more health officials implored parents to follow the recommendation, the worse peanut allergies got. The number of children going to the emergency department because of peanut allergies tripled in just one decade (2005–14). It spread like a virus. By 2019, one report estimated that one in every 18 American children had a peanut allergy. Schools began to ban peanuts and regulators met to purge peanuts from childhood snacks as EpiPen sales soared. Pharma exploited the situation by price-gouging the desperate parents and schools. Mylan Pharmaceuticals jacked up the price of an EpiPen from $100 to $600 in the U.S. (It’s $30 in some countries.)

The AAP recommendation had created a vicious cycle. The more prevalent peanut allergies became, the more people avoided peanuts for young children. This, in turn, caused more peanut allergies. Tunnel-vision thinking had created a nightmare scenario for which the only possible solution seemed to be the total eradication of peanuts from the planet.

As things got worse, a dissenting Lack decided to conduct a clinical trial randomizing infants to peanut exposure (at 4-11 months of age) versus no peanut exposure. He found that early peanut exposure resulted in an 86 percent reduction in peanut allergies by the time the child reached age 5 compared to children who followed the AAP recommendation. He blasted his findings to the world in a New England Journal of Medicine publication in 2015, finally proving what immunologists like Buckley had known for decades: Peanut abstinence causes peanut allergies. It was now undeniable; the AAP had it backward.

I reached out to Lack and had breakfast with him when he was traveling to Washington, D.C., for a medical conference in 2024. He told me that his initial hypothesis had been based on an early observation as a pediatrician that kids who got their ears pierced sometimes developed a nickel allergy around the piercing. But kids who had orthodontics didn’t. He realized that kids with orthodontics had prior exposure to nickel in the braces, making them immune. This observation was consistent with the concept of “oral tolerance” that he’d studied in mice experiments conducted at the University of Colorado in the 1990s.

He had an interesting observation from his childhood that reminded him that conventional wisdom can change. His grandfather had a heart attack, which doctors treated with strict bed rest — a recommendation that was eventually replaced with cardiac rehab exercise. As a 6-year-old, Lack recalled that his grandfather was not allowed to leave his bed. The family members had to take him his meals. His doctors managed his damaged heart by weakening it further.

“In science, we tend to get in a rut and then dig in,” he told me. “We have to be open-minded.”

Lack is now recognized as a hero in the field of allergy. But when he did his big study, he was heavily criticized.

It would take the AAP two years after Lack’s randomized trial was published to reverse its 2000 guidance for pediatricians and parents. It would also take two years for the NIH’s NIAID division to issue a report supporting the reversal.

Did they really need two years? Where was the sense of deep remorse? The affected families deserved to have the medical establishment move with a sense of urgency to correct their recommendation immediately following Lack’s definitive study. Hugh Sampson, another trainee of Rebecca Buckley, led the NIAID report that undid the recommendation. He told me that working with the government agency was frustrating. Sampson is one of the country’s leading allergists. When I asked him what he thought about the entire saga, he told me, “The food allergy community has been appropriately chastised [for getting the peanut recommendation wrong].”

An entire generation — millions of children — had been harmed by groupthink, and many still are feeling the effects. Now, at least the faucet of bad advice was turned off.

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