BACKGROUND: Altered gut microbiota (GM) profiles have been documented in children with food allergies (FA) and experiencing malnutrition. This study explored the GM composition in children with FA across varying degrees of malnutrition including those without malnutrition and those with different severity levels. METHODS: Fresh faecal samples were collected from 120 children aged 1-6 years, including 40 FA children with adequate weight (FANM), 40 FA children with malnutrition (FAM), and 40 healthy controls. The hypervariable region of the 16 S rDNA gene was subsequently sequenced to assess bacterial communities. RESULTS: Compared with healthy controls, the FANM group displayed a greater increase in the alpha diversity index. The FAM group exhibited an increase in seven genera, including Alistipes and Parabacteroides, compared to the control group, whereas nine genera were enriched in the FANM group. An analysis of clinical characteristics revealed a positive correlation between the relative abundance of the genus Faecalibacterium and the total IgE level. Fourteen pivotal microbial markers demonstrated substantial classification potential (AUC: 89.86%, 95% CI: 76.40-99.73% for FAM
AUC: 88.92%, 95% CI: 73.58-99.65% for FANM). CONCLUSION: FA children exhibit distinct GM profiles depending on the presence of malnutrition, which suggests the need for tailored microbiota-targeted therapies.