Sam Berk ’28
Today, the American Academy of Pediatrics (AAP) recommends that infants at high risk for peanut allergy be exposed to the legume as early as 4-6 months old. This recommendation, however, proves a stark contrast to previous advice given by the organization. In 2000, the AAP recommended that children at high risk for the allergy refrain from consuming peanuts until at least 3 years old. 8 years later – in 2008 – the AAP rescinded their recommendation. Despite the withdrawal of the AAP’s recommendation, the United States medical community continued to follow their 2000 advice. Pediatricians continued to recommend avoidance, and parents continued to avoid the feared allergen. In fact, in my home state of Massachusetts, a 2019 study found that 56.6% of schools ban peanuts.
Yet, now, the medical community has completely changed its approach to allergy avoidance. Due to the findings of a 2015 study entitled Learning Early About Peanut Allergy (LEAP), and its 2008 precursor “Early consumption of peanuts in infancy is associated with a low prevalence of peanut allergy,” it is absolutely clear that peanut avoidance most certainly does not aid in avoidance of anaphylaxis. The studies completely revolutionized understanding of the peanut allergy. The 2008 study, which was based in London, sought to understand the relationship between infant peanut exposure and subsequent development of a peanut allergy. The idea for the study was sparked by Dr. Gideon Lack, a professor of paediatric allergy at King’s College in London. Upon a visit to Israel in 2000, Lack discovered something astonishing. Among around 200 Israeli pediatricians, only a handful were regularly diagnosing peanut allergies. Meanwhile, back in the U.K., the vast majority of pediatricians were encountering peanut allergies in their patients. Perplexed, Lack set out to understand what was causing this massive discrepancy. Thus, the LEAP study was born.
The question at hand: when controlling for gene pool, what was leading to a much higher rate of peanut allergy in the UK than in Israel? Along with colleague and co-investigator Dr. George Du Toit in the UK and peers in Israel, Lack began to recruit patients. In December 2006, just under a year after I was born, my parents enrolled me in the LEAP study— the very first patient recruited in the U.K. Two years later, the researchers’ first monumental paper was published. By surveying 5171 Jewish schoolchildren in the UK and 5615 in Israel, as well as 77 weaning infants in the UK and 99 in Israel, the Du Toit et al. uncovered that the prevalence of peanut allergy in the UK was 10 times that in Israel, confirming Lack’s observation. Additionally, the study found that peanuts are more common in the diet of Israeli children than they are in the diet of British children. This exposure to peanuts in Israel came most often from one snack – bamba (basically a cheese puff but with peanut powder instead). Specifically, “the median monthly consumption of peanut in Israeli infants aged 8 to 14 months is 7.1 g of peanut protein, and it is 0 g in the UK (P < .001). The median number of times peanut is eaten per month was 8 in Israel and 0 in the UK (P < .0001).” While the researchers had found a correlation, it would take years more testing to prove to the global medical community that peanut exposure could help prevent peanut allergy.
Continuing their research in the U.K., Lack and Du Toit followed 640 infants until they were five years old. Each infant was deemed at “high risk” for peanut allergy due to preexisting conditions like egg allergy or severe eczema. Infants were randomly assigned to a group – avoidance (like me!) or consumption. The study’s findings were revolutionary. By the time they were 5, about 13.7% of the infants in the avoidance group who had previously shown no sign of a peanut allergy had developed an adverse reaction to peanuts. Simultaneously, only 1.9% of those in the consumption group who had shown no previous sign of peanut allergy developed a reaction by the end of the study. Additionally, those infants in the consumption group were more likely to have developed increased levels of the IgG4 antibody, connecting to peanut tolerance. At the same time, infants in the avoidance group were found to have higher levels of the IgE antibody, which is a marker for peanut allergy.
So now, when parents follow their pediatricians’ advice worldwide and introduce peanut and other common allergens into their infants’ diets, they can thank Lack, Du Toit, and Bamba, the Israeli snack that sparked it all.
Sam Berk is a staff writer at The Princeton Medical Review. She can be reached at sberk@princeton.edu
References
American Academy of Pediatrics. (2017, January). New guidelines detail use of ‘infant‑safe’ peanut to prevent allergy. AAP News. Retrieved from https://publications.aap.org/aapnews/news/12250/New-guidelines-detail-use-of-infant-safe-peanut-to?autologincheck=redirected
Bartnikas, L. M., Huffaker, M. F., Sheehan, W. J., Kanchongkittiphon, W., Petty, C. R., Leibowitz, R., Young, M. C., & Phipatanakul, W. (2020). Racial and socioeconomic differences in school peanut-free policies. Journal of Allergy and Clinical Immunology: In Practice, 8(1), 340–342.e1. https://doi.org/10.1016/j.jaip.2019.06.036
Du Toit, G., Katz, Y., Sasieni, P., Mesher, D., Maleki, S. J., Fisher, H. R., Fox, A. T., Turcanu, V., Amir, T., Zadik-Mnuhin, G., Cohen, A., Livne, I., & Lack, G. (2008). Early consumption of peanuts in infancy is associated with a low prevalence of peanut allergy. Journal of Allergy and Clinical Immunology, 122(5), 984–991. https://doi.org/10.1016/j.jaci.2008.08.039
Food Allergy Research & Education. (n.d.). Learning early about peanut allergy (LEAP). Retrieved June 23, 2025, from https://www.foodallergy.org/resources/learning-early-about-peanut-allergy-leapMakary, M. (2024, September). How pediatricians created the peanut allergy epidemic. The Wall Street Journal. Retrieved from https://www.wsj.com/health/how-pediatricians-created-the-peanut-allergy-epidemic-952831c4
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