Boston Children’s Hospital reported early clinical evidence that oral, encapsulated fecal microbiome transplantation may raise peanut tolerance in a Phase 1 open-label study. Published in Science Translational Medicine, the trial tested frozen FMT capsules in 15 adults with baseline reactivity to 100 mg or less of peanut protein. In the non-antibiotic cohort, three participants met an increased peanut reactivity threshold after a one-time dose; in the antibiotic-pretreated cohort, three of five also showed improved tolerance without reported safety problems. Across all participants, six met a secondary efficacy endpoint, with responses persisting through the four-month endpoint. Mechanistic analyses suggested a shift toward tolerogenic immunity, including increased RORγt-positive regulatory T cells and decreased type 2 helper T cells in responders, supporting the rationale for using bile acid metabolites and microbiome-mediated immune modulation to restore oral tolerance.