Causal foods shape the tolerance timeline in food protein-induced allergic proctocolitis

Published online June 16, 2025

Food protein induced allergic proctocolitis (FPIAP) is a non-IgE-mediated food allergy characterized by benign bloody and mucousy stools in the first few months of life. Although most children eventually grow out of FPIAP, families and clinicians often wonder when tolerance occurs. Previous studies have largely focused on cow’s milk, leaving limited knowledge about the timing of tolerance to other causal foods, the role of multiple food triggers, and additional factors contributing to the timing of tolerance.

In a recent study published in The Journal of Allergy and Clinical Immunology: In Practice, Iskender et al. followed 91 infants with FPIAP at Kocaeli University in Turkey for at least three years. Using a structured protocol, the researchers systematically reintroduced causal food(s) to determine when tolerance occurred. They assessed tolerance timelines for cow’s milk, egg, beef, wheat, and nuts, and examined how combinations of food triggers and clinical factors influenced recovery.

The study found that the median age of tolerance was around 15 months overall, but this varied by causal food. Cow’s milk, beef, and wheat allergies resolved earlier, whereas egg and nut allergies persisted longer. Importantly, the presence of multiple food allergies did not always indicate delayed tolerance. Instead, the specific food involved in multiple allergies seemed to play a key role. Among infants with multiple food allergies, egg was linked to slower resolution, whereas beef was not. 

Other factors linked to later tolerance included having atopic dermatitis (eczema) at diagnosis, the absence of a household pet, and the coexistence of IgE-mediated food allergy. Notably, infants with FPIAP who also had eczema were more likely to develop IgE-mediated food allergies over time, which in turn increased the risk of multiple food allergies and prolonged tolerance development.

These findings provide valuable guidance for clinicians and families on when to safely attempt causal food reintroduction. They highlight that the type of causal food, rather than the number of foods, may be key determinant of recovery pace. Furthermore, the coexistence of atopic dermatitis and IgE-mediated food allergy could shift the course of FPIAP towards a more persistent disease.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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