Lead
Before 2015, the conventional wisdom was simple: introduce peanuts later, avoid the sensitive period, and you reduce the risk. Then a randomized controlled trial overturned that premise in a single publication.
The LEAP trial showed the opposite: in high-risk infants, early introduction of peanuts reduced the rate of peanut allergy — by a striking margin. The major allergy guidelines were rewritten. The received wisdom flipped from "delay for safety" to "early introduction, done correctly, is protective."
That shift comes with an important qualification: it is stratified by risk level, and the recommendation is not a single "safe at X months" for everyone. This article unpacks the structure of that stratification and shows what parents can concretely do to find their footing.
Background: Why Peanut Allergy Matters
Peanut allergy is known among food allergies for its high likelihood of triggering severe anaphylaxis: a severe, rapidly developing allergic reaction that can cause breathing difficulty, drop in blood pressure, and shock — a medical emergency and its low rate of natural resolution (low tolerance acquisition). In a 2020 survey by the Japanese Society of Pediatric Allergy and Clinical Immunology, peanuts accounted for approximately 6% of causative foods, placing them fourth after egg, cow's milk, and wheat [7].
The older view held that early exposure in infancy promoted sensitization and allergy development, leading to recommendations that introduction be delayed. The LEAP trial tested that hypothesis directly.
What the LEAP Trial Showed
In 2015, Du Toit and colleagues published the results of the LEAP (Learning Early About Peanut Allergy) trial in the New England Journal of Medicine [1].
The study enrolled 640 infants aged 4–11 months with severe atopic dermatitis: a chronic, itchy inflammatory skin condition (eczema) common in childhood, often associated with allergies and asthma, egg allergy, or both. After confirming minimal or absent peanut sensitization via skin prick test: an allergy test where a small drop of allergen is pricked into the skin to see if a raised bump (wheal) forms, the infants were randomly assigned to either an early-introduction group (consuming peanut-containing foods at least three times a week from enrollment) or an avoidance group. Peanut allergy rates were compared at age 5.
The result in the overall trial population (all 640 participants): 3.2% allergy in the early-introduction group versus 17.2% in the avoidance group — a relative risk reduction of 81% [1]. In the subgroup of infants who were skin prick test (SPT)-negative (no pre-existing sensitization), the reduction was even greater: 1.9% versus 13.7%, a relative risk reduction of 86.1% [1]. The "86%" figure sometimes seen in summaries refers to this SPT-negative subgroup; both numbers appear in the original paper and reflect different denominators. Even in high-risk children, early introduction was powerfully protective.
In 2016, the LEAP-On trial confirmed that the protective effect persisted even after the early-introduction group stopped consuming peanuts for 12 months [2]. The immunological change was not temporary.
Relevant evidence also comes from Japan. The PETIT trial, published by Natsume and colleagues in The Lancet in 2017, enrolled Japanese infants with eczema and showed that early introduction of heated egg powder reduced egg allergy development by 79% [3]. Although the allergen was egg rather than peanut, the direction — early introduction as prevention — aligns with LEAP and is cited in Japanese clinical practice as evidence for the early-introduction approach more broadly.
A systematic review and meta-analysis by Ierodiakonou and colleagues in JAMA (2016) extended this to multiple allergens, showing that early introduction was associated with reduced allergy risk across food types [6].
The NIAID 2017 Guidelines: Three Risk Tiers
In response to LEAP, the National Institute of Allergy and Infectious Diseases (NIAID) published addendum guidelines in 2017, organizing peanut allergy prevention recommendations around three risk tiers [4].
High risk (severe atopic dermatitis, egg allergy, or both) Early introduction at 4–6 months is recommended, but introduction should be preceded by specialist allergy evaluation (skin prick test or specific IgE testing). Depending on test results, introduction under an oral food challenge: a supervised medical test where a suspect food is given in gradually increasing amounts to confirm or rule out allergy under monitored conditions in a medical setting may be indicated [4]. In this group, consultation with an allergist before introducing peanuts is required.
Moderate risk (mild-to-moderate atopic dermatitis) Early introduction at home starting around 6 months is appropriate. Specialist evaluation before introduction is not required, though consultation is encouraged for those who have concerns [4].
Low risk (no atopic dermatitis, no egg allergy) Introduction can follow the normal timeline of solid food introduction. No special testing or pre-consultation is obligatory [4].
The Japanese Society of Pediatric Allergy and Clinical Immunology's Food Allergy Clinical Practice Guideline 2021 also acknowledges the evidence for early introduction and recommends a risk-stratified approach [7]. The broad framework aligns with the NIAID tiering, though the specific procedures are best confirmed with a local pediatrician or allergist.
Safe Forms: The Choking Risk Is Real
The guidelines' recommendation to "introduce" peanuts is not a recommendation to give whole peanuts to an infant. This distinction matters.
Whole peanuts must never be given to infants or toddlers. The choking risk is high. Peanut butter applied directly from a spoon also poses a risk: the paste is viscous enough to cause airway obstruction [4].
Safe forms for introduction, as indicated by guidelines and clinical practice:
- Peanut powder (finely ground peanut) dissolved in water or purée to form a thin paste
- A small amount of peanut butter thinned into infant food (rice porridge, vegetable purée)
- Commercial peanut powder products mixed into solid food
The standard recommendation is to offer the first introduction in the morning on a day when the child is well, in an environment where a response could be managed if one occurred.
Finding Your Starting Point
The first step is identifying which tier your infant falls into.
If your infant has severe eczema or a diagnosed egg allergy, consult a pediatrician or allergist before introducing peanuts. The current direction is not "delay for safety" but "introduce early, in consultation with a specialist, at the right time."
If your infant has neither eczema nor egg allergy, introducing a small amount of peanut powder mixed into solid food starting around 6 months is the approach consistent with current guidance.
If you are uncertain, a single question — "Which risk tier is my child in?" — asked at the 4–6 month well-child visit (Japan: the sanshigo kenshin, or 3–4 month checkup, is the preceding appointment; the 6–7 month visit follows) is the lowest-cost action available.
Summary
The LEAP trial made a prior assumption — that delaying peanut introduction was the safer choice — untenable [1]. Evidence for early introduction as prevention has accumulated, and the NIAID 2017 guidelines systematized that evidence into a risk-stratified framework [4].
High-risk infants should not make this decision without specialist guidance. "Introduce early" and "do it at home without consultation" are two different propositions.
For low-risk infants, introducing a small amount of peanut powder mixed into solid food starting around 6 months is consistent with current scientific consensus. The form must be paste or powder. Whole peanuts are not an option.
Evidence changes. Older books and parenting websites may still reflect the pre-2015 recommendation. Checking the date on any information you read is a useful habit — here more than most.
References
- Du Toit G, Roberts G, Sayre PH, et al. Randomized trial of peanut consumption in infants at risk for peanut allergy. N Engl J Med. 2015;372(9):803–813. doi:10.1056/NEJMoa1414850. PMID: 25705822.
- Du Toit G, Sayre PH, Roberts G, et al. Effect of avoidance on peanut allergy after early peanut consumption. N Engl J Med. 2016;374(15):1435–1443. doi:10.1056/NEJMoa1514209. PMID: 26942922.
- Natsume O, Kabashima S, Nakazato J, et al. Two-step egg introduction for prevention of egg allergy in high-risk infants with eczema (PETIT): a randomised, double-blind, placebo-controlled trial. Lancet. 2017;389(10066):276–286. doi:10.1016/S0140-6736(16)31418-0. PMID: 27939035.
- Togias A, Cooper SF, Acebal ML, et al. Addendum guidelines for the prevention of peanut allergy in the United States: report of the National Institute of Allergy and Infectious Diseases–sponsored expert panel. J Allergy Clin Immunol. 2017;139(1):29–44. doi:10.1016/j.jaci.2016.10.010. PMID: 28065278.
- Perkin MR, Logan K, Tseng A, et al. Randomized trial of introduction of allergenic foods in breast-fed infants. N Engl J Med. 2016;374(18):1733–1743. doi:10.1056/NEJMoa1514210. PMID: 27028911.
- Ierodiakonou D, Garcia-Larsen V, Logan A, et al. Timing of allergenic food introduction to the infant diet and risk of allergic or autoimmune disease: a systematic review and meta-analysis. JAMA. 2016;316(11):1181–1192. doi:10.1001/jama.2016.12623. PMID: 27654604.
- Japanese Society of Pediatric Allergy and Clinical Immunology. Food Allergy Clinical Practice Guideline 2021. Tokyo: Kyowa Kikaku; 2021.