BACKGROUND: Food protein- induced enterocolitis syndrome (FPIES), a non-IgE-mediated- IgE-mediated allergy, primarily affects infants and young children. Whether and when tolerance develops seems to vary among populations and trigger foods. OBJECTIVE: This study aimed to evaluate tolerance development and its assessment in a Swedish cohort. METHODS: This was a prospective follow-up study of a Swedish cohort of 113 children, followed at 25 pediatric departments, with acute FPIES. Data on oral food challenges and FPIES resolution were collected through chart reviews and, if incomplete, supplemental caregiver interviews. RESULTS: The median age at last follow-up was 5.6 years (range: 8.7 months to 16.5 years). Eighty-three children (73%) developed tolerance to 96 of 137 (70%) foods: 93% for cow's ' s milk, 92% for oat, and 46% for fi sh. The median age when tolerance was developed was 36.0 months (interquartile range: 23.7-48.2 months): 24.4 months for cow's ' s milk, 30.1 months for oat, and 49.4 months for fi sh. Tolerance was determined in hospital in 45% of cases. Five percent demonstrated allergic sensitization to their FPIES trigger food. Age at tolerance development did not differ between sensitized and nonsensitized patients. CONCLUSIONS: Most of the children in this Swedish cohort with FPIES achieved tolerance before age 4 years. Cow's milk- and oat-induced FPIES had similar remission patterns, with early resolution. Development of tolerance to fish occurred significantly later compared with all other FPIES-inducing foods. (c) 2024 American Academy of Allergy, Asthma & Immunology