Science got peanut allergies all wrong – until the scientific method got it right

By_Suraj Karowa/ ANW , November 4, 2025 

For decades, parents were warned to shield babies from peanuts to prevent life-threatening allergies. New research reveals that advice was dead wrong – and flipping it has slashed U.S. peanut allergy rates by up to 43% in young children, potentially sparing tens of thousands from the condition.

The turnaround stems from the work of Dr. Gideon Lack, a London-based allergist whose curiosity was piqued 25 years ago during a lecture in Tel Aviv, Israel. While U.S. and U.K. peanut allergies affected over 2% of kids, Israeli doctors reported almost none. “Virtually every doctor in London had a peanut-allergic patient,” Lack told reporters.

“In Tel Aviv, out of 200, only two or three raised their hands.”
Lack zeroed in on a cultural quirk: Israeli infants devour Bamba, peanut-flavored puff snacks, starting at 4-6 months. “Mother, father, Bamba” is a local joke – but a revealing one. U.K. babies ate zero grams of peanut weekly; Israeli ones consumed about 2 grams, equivalent to 10 peanuts.

To test genetics versus environment, Lack’s team surveyed 5,000 Jewish schoolkids in London and 5,000 in Israel. U.K. rates were 10 times higher (nearly 2% vs. near-zero). Published in 2008 in the Journal of Allergy and Clinical Immunology, the study showed association, not causation. Funding came from the National Peanut Board amid skepticism – critics called early exposure “preposterous” and “unethical.”

Proof required a gold-standard trial. The LEAP study, funded by the U.S. National Institute of Allergy and Infectious Diseases (NIAID), enrolled 640 high-risk infants (with severe eczema or egg allergy) from 4-11 months old. Half consumed peanut products like Bamba regularly until age 5; half avoided them.

Results, published in 2015 in the New England Journal of Medicine, stunned researchers: Among peanut-tolerant starters, avoidance led to 13.7% allergy rate by age 5; early consumption dropped it to 1.9% – an 86% reduction. For sensitive infants, avoidance yielded 35.3% allergies; exposure cut it to 10.6% – a 70% drop. “I hoped for an effect, but not over 80%,” Lack said, recalling toasting with whiskey and roasted peanuts.

This upended 2000 American Academy of Pediatrics (AAP) guidelines delaying peanuts until age 3 for high-risk kids. AAP withdrew avoidance advice in 2008, then endorsed early introduction post-LEAP in 2015, refining it in 2017 and 2021.

Impact is measurable. A Pediatrics study last month tracked U.S. kids under 3: Peanut allergies fell 33% after 2015 guidelines, 43% after 2017. From top food allergy, peanuts slipped to second behind eggs. Extrapolated nationally, nearly 40,000 children avoided diagnosis, per lead author Dr. David Hill of Children’s Hospital of Philadelphia.

“Early gut exposure teaches tolerance,” Hill explained. “Skin exposure via eczema sensitizes.” This “dual-exposure hypothesis” underpins Lack’s ongoing SEAL trial (NIAID-funded), treating infant eczema early with moisturizers and steroids to block skin sensitization, then introducing foods orally.

Medicine’s path is zigzag, Lack notes. He followed old avoidance rules with his sons – “wrong in retrospect.” Yet science self-corrected through observation, hypothesis, controlled trials, and guideline shifts.

Peanut allergy hospitalizations and costs once soared; now, incidence plummets. For parents: Consult pediatricians, but evidence favors safe, early peanut introduction (e.g., thinned peanut butter) for most infants by 4-6 months, especially high-risk ones after allergy screening.

The Bamba lesson? Sometimes, the snack that seems risky is the safeguard. As Lack puts it: Knocking on the immune system’s front door (via mouth) gets a welcome; breaking in through the window (skin) triggers alarm.