Severe food allergic reactions in infants may stem from disrupted gut bacterial communities established in the first months of life. Food protein-induced enterocolitis syndrome (FPIES) represents one of the most serious non-IgE food allergies, causing vomiting, diarrhea, and dehydration severe enough to require emergency care when infants consume triggering foods like milk or rice.
Researchers analyzing fecal samples from 56 newly diagnosed FPIES patients found distinct microbial signatures compared to healthy controls. Children with FPIES showed significantly reduced levels of Bifidobacterium, beneficial bacteria that typically dominate healthy infant guts and support immune system maturation. Simultaneously, these children harbored elevated populations of Bacteroides, Haemophilus, and Veillonella species. The most severe food triggers correlated with particularly low levels of Verrucomicrobiota, another protective bacterial family.
This microbial disruption pattern suggests FPIES may result from incomplete colonization by symbiotic bacteria rather than simple overgrowth of harmful species. The timing proves critical—these bacterial imbalances were detectable at diagnosis, typically occurring between 4-12 months when complementary foods are introduced. The findings align with the hygiene hypothesis and growing evidence that early antibiotic exposure or cesarean delivery can disrupt protective microbial establishment. However, this cross-sectional study cannot determine whether microbial dysbiosis causes FPIES or results from it. The research opens intriguing possibilities for microbiome-based interventions, potentially including targeted probiotic supplementation with Bifidobacterium strains, though clinical trials would be needed to establish therapeutic efficacy and safety in this vulnerable population.