Efficacy of Bifidobacterium lactis BLa80 in preventing early childhood eczema and respiratory infections via gut microbiome and immune modulation

Background Early childhood is a critical period for immune development, with eczema and respiratory infections representing common health challenges. This study investigated the efficacy of Bifidobacterium animalis subsp. lactis BLa80 in reducing these conditions potentially through gut microbiome modulation. Methods In a randomized, double-blind, placebo-controlled trial, 360 formula-fed infants and children aged below 3 years old with elevated allergy risk received daily B. lactis BLa80 (5 × 10 9 CFU) or placebo for 180 days. Primary outcomes included eczema incidence and symptom burden, with secondary outcomes assessing respiratory infections, gastrointestinal symptoms, gut microbiota composition (16S rRNA sequencing), functional pathways (KEGG analysis), and fecal immune markers (ELISA). Results The probiotic group demonstrated significantly reduced eczema incidence (27.6% vs. 69.5%, RR: 0.398, p 0.001) and upper respiratory tract infections (19.4% vs. 42.5%, RR: 0.457, p 0.001). Significant reductions were observed in symptom burden, including nasal congestion, vomiting, milk aspiration, and irritability. Microbiota profiling showed enrichment of beneficial taxa ( Akkermansia, Fusicatenibacter ) with enhanced metabolic pathways including tryptophan metabolism, vitamin biosynthesis, and xenobiotic degradation. Immunological profiling showed maintained human beta-defensin-2 ( p = 0.005), increased secretory IgA ( p 0.001), and reduced calprotectin ( p 0.001). Conclusions B. lactis BLa80 supplementation effectively reduces eczema and respiratory infections associated with gut microbiome remodeling that may enhance barrier function, immune regulation, and metabolic capacity, supporting its use as a preventive nutritional strategy in early childhood. Clinical Trial Registration ChiCTR2300074956.