Scientific Study

Rationale: The Dual Allergen Exposure Hypothesis proposes that food allergy develops due to cutaneous exposure in the absence of oral consumption. Evaluation of the younger siblings of the Learning Early About Peanut (LEAP) participants provides an opportunity to understand the impact of environmental exposure to peanut during infancy and early childhood on the development of peanut sensitization and allergy through a prospective randomized trial of high environmental versus low environmental peanut exposure. Methods: LEAP-Trio evaluated the allergic status of younger siblings who resided in the home of LEAP participants at any time during the LEAP intervention. The primary endpoint was sensitization (defined as skin prick test ≥ 3 mm, peanut specific-IgE ≥ 0.35 kU/L, or Ara h2 ≥ 0.1 kU/L). Results: 144 younger siblings of LEAP avoiders and 154 younger siblings of LEAP consumers participated. Younger siblings of consumers had a higher rate of sensitization than younger siblings of avoiders, 30.4% (41/135) versus 20.0% (26/130) P=0.055, and a higher rate of allergy, 10.0% (15/150) versus 5.0% (7/140) P=0.116. Among younger siblings of LEAP consumers, younger siblings that introduced peanut in the first year of life had a significantly lower rate of sensitization than younger siblings that did not introduce peanut, 18.3% (13/71) versus 44.4% (28/63) (P=0.002). No differences were found in egg or milk sensitization between groups. Conclusions: There was a trend toward increased sensitization and allergy in younger siblings of LEAP consumers, an effect that was greatly reduced if the younger sibling introduced peanut early. https://doi.org/10.1016/j.jaci.2023.11.876