The Medical Establishment Closes Ranks, and Patients Feel the Effects

You probably know about the surge in childhood peanut allergies. Peanut allergies in American children more than tripled between 1997 and 2008, after doctors told pregnant and lactating women to avoid eating peanuts and parents to avoid feeding them to children under 3. This was based on guidance issued by the American Academy of Pediatrics in 2000.

You probably also know that this guidance, following similar guidance in Britain, turned out to be entirely wrong and, in fact, avoiding peanuts caused many of those allergies in the first place.

That should not have been surprising, because the advice violated a basic principle of immunology: Early exposure to foreign molecules builds resistance. In Israel, where babies are regularly fed peanuts, peanut allergies are rare. Moreover, at least one of the studies on which the British advice was based showed the opposite of what the guidance specified.

As early as 1998, Gideon Lack, a British pediatric allergist and immunologist, challenged the guidelines, saying they were “not evidence-based.” But for years, many doctors dismissed Dr. Lack’s findings, even calling his studies that introduced peanut butter early to babies unethical.

When I first reported on peanut allergies in 2006, doctors expressed a wide range of theories, at the same time that the “hygiene hypothesis,” which holds that overly sterile environments can trigger allergic responses, was gaining traction. Still, the guidance I got from my pediatrician when my second child was born that same year was firmly “no peanuts.”

It wasn’t until 2008, when Lack and his colleagues published a study showing that babies who ate peanuts were less likely to have allergies, that the A.A.P. issued a report, acknowledging there was a “lack of evidence” for its advice regarding pregnant women. But it stopped short of telling parents to feed babies peanuts as a means of prevention. Finally, in 2017, following yet another definitive study by Lack, the A.A.P. fully reversed its early position, now telling parents to feed their children peanuts early.