Why is this interesting? - The Allergy Edition

On peanuts, kids, and the complexities of human health

Noah here. If you have kids—and likely even if you don’t—you know about the prevalence of peanut allergies. Every school my kid has attended has been a “nut-free zone,” and most other environments like airplanes and restaurants go out of their way to either avoid them entirely or else let everyone know they may be in the area.

The reason is simple: more kids are developing serious allergies, and no one is quite sure why. In developing countries, food allergy levels are as high as 10%. For a while, the popular theory was the “hygiene hypothesis,” which, in its original 1989 form, suggested that we were basically too clean for our own good. “Over the past century declining family size, improvements in household amenities, and higher standards of personal cleanliness have reduced the opportunity for cross infection in young families,” wrote British epidemiologist David Strachan in his original comment. “This may have resulted in more widespread clinical expression of atopic disease, emerging earlier in wealthier people, as seems to have occurred for hay fever.”

Chart from A global survey of changing patterns of food allergy burden in children

The hygiene hypothesis has tended to manifest itself as something along the lines of “in my day we ate dirt instead of playing video games,” which may accidentally turn out to be a more accurate reading of the situation. As scientists have dug deeper into the hygiene hypothesis, they’ve come to believe it has a lot less to do with our cleanliness and more to do with our microbes. Here’s how it was described in a 2017 news feature for the Proceedings of the National Academy of Sciences:

“We know an awful lot now about why our immune system’s regulation is not in terribly good shape, and it’s got absolutely nothing to do with hygiene,” says Graham Rook, an emeritus professor of medical microbiology at University College London. Today, epidemiological, experimental, and molecular evidence support a different hypothesis: Early exposure to a diverse range of “friendly” microbes—not infectious pathogens—is necessary to train the human immune system to react appropriately to stimuli.

If this new hypothesis is true, then cutting back on personal hygiene will not have an impact on rates of chronic inflammatory and allergic disorders; it will, however, increase infections. The hygiene hypothesis is a “dangerous misnomer which is misleading people away from finding the true causes of these rises in allergic disease,” says Sally Bloomfield, chair of the International Scientific Forum on Home Hygiene and an honorary professor at the London School of Hygiene and Tropical Medicine. “I’ve even seen things in the media saying we shouldn’t wash our hands. What the hell are they talking about?”

Why is this interesting?

At this point, there seems to be some agreement that part of the allergy problem is that we are keeping kids away from highly-allergic foods like peanuts. In 2000 the American Academy of Pediatrics (AAP) recommended children at high risk of peanut allergy to avoid the food before turning three. In 2015, the AAP and others changed their position to suggest that certain groups of children should have peanuts earlier (not all, and obviously WITI is not medical advice). “There is now scientific evidence,” they wrote, “that health care providers should recommend introducing peanut-containing products into the diets of ‘high-risk’ infants early on in life (between 4 and 11 months of age) in countries where peanut allergy is prevalent because delaying the introduction of peanut can be associated with an increased risk of peanut allergy.”

For those of you with kids, much of this background may sound familiar. What was new to me was this explanation from a recent BBC article about why this approach of not having children eat peanuts early would present such an issue:

The reason is that just because an infant does not eat peanuts does not mean that they won't encounter people who have. The child can be exposed to peanuts through dust, contact with furniture, and even creams containing peanut oil. If the child has not eaten peanuts, this contact with the skin can trigger a response from their immune system.

“If you've got a little infant with early-onset eczema and the parents are eating peanuts without washing their hands and then handling the baby, the baby can get sensitised through the broken skin,” says Amena Warner, head of clinical services at Allergy UK. When the child then eats the food, the immune system perceives it as a threat and attacks. Nadeau has turned this wisdom into a memorable rhyme: “Through the skin allergies begin; through the diet allergies can stay quiet.”

This is why, especially for children with eczema, experts are unanimous: a diverse range of foods should be introduced through weaning from around three or four months of age. “There is this window of opportunity in the early years to establish tolerance,” says Alexandra Santos, an associate professor in paediatric allergy at King's College London. She helped demonstrate through a Learning Early About Peanut Allergy study that introducing peanuts between four and 11 months gave five-year-old children an 80% lower chance of having peanut allergy.

Another reminder that our bodies, and the world they exist in, is an incredibly complex ecosystem. Like much of science, as much as we now know, particularly when compared with where we were thirty or fifty years ago, there are still large areas of medicine with plenty left to discover. (NRB)

Clever Project of the Day:

Like every member’s club and co-working space in New York, Neuehouse needed to pivot. This nicely designed space, in front of the club, allows for socially distanced meetings and a spot to hang out and read. We also liked the story behind the design told recently by CEO Josh Wyatt: “The Longhouse was designed in collaboration with NeueHouse members at architecture firm BVN as part of their Re-Ply concept launched early this summer. Re-Ply is an architectural initiative conceived to dismantle the very material that has been used as barricades to protect businesses during protests and transforming it into communal spaces...” (CJN)

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Thanks for reading,

Noah (NRB) & Colin (CJN)

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