LEAP Trial
Design. LEAP (Learning Early About Peanut Allergy; Du Toit, Roberts, Sayre, Lack et al., NEJM 2015) was a single-site, open-label randomised trial in London, overseen by the NIAID. It enrolled 640 infants aged 4 to under 11 months (median 7.8 months) who were at high risk because they had severe eczema, egg allergy or both. Babies were split by baseline peanut skin-prick test: 542 with no wheal and 98 with a 1–4 mm wheal. Infants with wheals larger than 4 mm (76 of 834 screened) were excluded as probably already allergic. Each cohort was randomised to eat peanut (≥6 g peanut protein a week, mostly as Bamba puffs or smooth peanut butter) or to avoid it until 60 months. The outcome was peanut allergy on Oral Food Challenge at 5 years. 98.4% of children were followed up.
LEAP Trial [relates] Atopic Dermatitis LEAP Trial [relates] Skin Prick Testing
Results. In the skin-test-negative cohort, peanut allergy at 5 years was 13.7% with avoidance against 1.9% with consumption (absolute difference 11.8 points; 86.1% relative reduction; P<0.001; NNT about 8.5). In the 1–4 mm cohort it was 35.3% against 10.6% (70% relative reduction; P=0.004). Combining both cohorts gives the often-quoted overall figure of about an 81% reduction (cited in the earlier stub). Serious adverse events and hospitalisations did not differ between groups. Eaters had more mild viral and skin infections, urticaria and gastroenteritis, none more severe. Peanut-specific IgG4 rose in eaters, while avoiders more often had high peanut IgE. Bed-dust peanut was still detectable in avoiders’ homes (median 4.1 µg/g), showing that they had skin and environmental exposure without eating it. The follow-on LEAP-On study found protection persisted after 12 months of stopping peanut (age 5–6), which suggests durable tolerance (NIAID 2017).
LEAP Trial [supports] Dual-Allergen Exposure Hypothesis LEAP Trial [prevents] Food Allergy LEAP Trial [contradicts] Elimination Diets
Impact on guidance. LEAP reversed the 1998–2000 UK/US advice to delay allergenic foods in high-risk infants. It led directly to the NIAID 2017 addendum guidelines (peanut at 4–6 months after evaluation for severe eczema/egg allergy; around 6 months for mild–moderate eczema), which the American Academy of Dermatology endorses in summary. It also underpins the 2018 BSACI/BDA guidance to introduce egg then peanut from about 4 months in infants with eczema. Together with the EAT Trial, it is the main evidence for the Dual-Allergen Exposure Hypothesis.
LEAP Trial [precedes] EAT Trial LEAP Trial [supports] American Academy of Dermatology
Limits and relevance to toddlers. LEAP tested prevention in infants, not treatment of established eczema. Peanut eating did not aim to improve the skin, and the trial does not show that feeding peanut helps a toddler’s rash. Its results do not cover infants with large wheals or children first assessed after age 1. 7 consumers were stopped at baseline because of a positive challenge, and 9 stopped later because of symptoms, so early introduction is not possible for every high-risk child. For parents of toddlers with eczema, the transferable lesson is that avoiding a tolerated food “to be safe” may raise the chance of allergy to it.
LEAP Trial [relates] Food Allergy
Connections
- Skin Barrier Dysfunction — supports the dual-allergen exposure hypothesis, source: Papapostolou 2022
- Dual-Allergen Exposure Hypothesis — key RCT evidence, source: Du Toit 2015
- Food Allergy — 86% relative reduction in peanut allergy (SPT-negative cohort), source: Du Toit 2015
- Skin Prick Testing — used to stratify and exclude (>4 mm), source: Du Toit 2015
- Oral Food Challenge — primary outcome measure at 60 months, source: Du Toit 2015
- EAT Trial — companion UK trial in general population, source: BSACI
- American Academy of Dermatology — NIAID 2017 addendum based on LEAP, source: AAD
- Elimination Diets — avoidance group had more peanut allergy, source: Du Toit 2015
- Tree Nut Allergy — unknown whether early tree-nut feeding prevents allergy, source: Nutrients 2024 review