In a famous “Peanuts” cartoon, a glum Charlie Brown sits alone on a bench, eating a sandwich; his thought bubble reads, “Nothing takes the taste out of peanut butter quite like unrequited love.” Charles Schulz was perhaps better than any other at simply and brilliantly capturing the timeless angst that defines the human condition. And yet peanut butter – what in his 1964 cartoon aptly represents one of the joys of childhood itself – might today more likely be considered one of childhood’s real hazards, with dramatically rising rates of peanut allergy afflicting children around the world.
While the prevalence of peanut allergy is clearly increasing, a definitive reason for this rise and how to reverse it have remained mysteries. In the effort to answer these questions, a group of investigators made an important observation: they found that Jewish children in the United Kingdom (UK) were 10 times as likely to develop a peanut allergy as compared with Israeli children of similar ancestry. Trying to understand why, they noted that in Israel, peanuts are usually introduced into the diet by 7 months of age; in the UK, peanuts are rarely introduced before age 1. This led to the hypothesis that early exposure to peanuts might be protective against peanut allergy. These investigators designed and conducted a trial, sponsored by the United States National Institute of Allergy and Infectious Disease that seems to have proven them correct.
The Learning Early About Peanut Allergy (LEAP) study, now published in NEJM, was a randomized, open-label, single-center study designed to compare two strategies to prevent peanut allergy: consumption or avoidance of peanuts. The trial enrolled children 4-11 months of age who were thought to be at high risk for developing a peanut allergy based on a history of severe eczema or egg allergy. Participants were given a skin prick test to evaluate for sensitivity to peanut. Children with a negative skin prick result (meaning no measureable skin wheal) or moderately positive (1-4mm wheal) were included in the study; children with a highly positive result (wheal >4mm) were excluded. Infants were then stratified based on their skin prick test results. 530 infants in the skin prick test negative group and 98 infants in the skin prick test positive group were randomly assigned to either consume 6g of peanut protein per week or to avoid peanuts. The primary outcome was the proportion of participants with a peanut allergy at age 5, determined by response to an oral peanut protein challenge.
The results were impressive: in the negative skin prick test group, the prevalence of peanut allergy at age 5 was 13.7% in the avoidance group versus 1.9% in the consumption group (P<0.001). In the positive skin prick test group, 35.3% of those who avoided peanuts were allergic as compared with 10.6% of the consumption group (P=0.004). There were no significant differences in hospitalizations or other serious adverse events between groups. The investigators did identify five categories of mild or moderate adverse events that were more common in the consumption group: upper respiratory tract infection, viral skin infection, gastroenteritis, urticaria, and conjunctivitis.
Dr. Jeffrey Drazen, Editor-in-Chief, describes these results as “important, new knowledge that provides practical answers about how to deal with peanut allergy specifically and also improves our understanding of the immunology of food allergy more generally.”
In an accompanying editorial, Drs. Rebecca Gruchalla and Hugh Sampson call the LEAP trial a “landmark study.” They write that some open questions remain –f or example, “If regular peanut consumption is discontinued for a prolonged period, will tolerance persist? Can the findings of the LEAP study be applied to other foods, such as milk, eggs, and tree nuts?” However, even before we have those answers, they conclude “the LEAP study makes it clear that we can do something now to reverse the increasing prevalence of peanut allergy” – offering hope that peanut butter might one day be restored to its symbolic place, representing an uncomplicated joy of childhood.