Oral <scp>PHGG</scp> ameliorates atopic dermatitis‐like dermatitis with concurrent modulation of colonic <scp>IgA</scp> and cecal microbiota: implications for the gut–skin axis

BACKGROUND: Atopic dermatitis (AD) is increasingly recognized as a systemic inflammatory disorder linked to intestinal immune and microbiome dysregulation. However, whether dietary galactomannan fibers can mitigate AD through coordinated modulation of the gut-skin axis remains unexplored. This study investigated the anti-atopic potential of orally administered partially hydrolyzed guar gum (PHGG), a low-viscosity, fermentable galactomannan enriched in low-mass oligosaccharides (mannose/galactose ratio of 1.87). RESULTS: ) attenuated lesion severity, epidermal hyperplasia, collagen loss, and mast cell infiltration without adverse effects on body weight or organ weights. PHGG reduced circulating immunoglobulins and inflammatory cytokines, suppressed skin type 2 helper T-cell (Th2)-associated mediators, and restored colonic immune homeostasis, as evidenced by increased immunoglobulin A (IgA) and decreased interleukin 1 beta (IL-1β) and IL-6. Cecal 16S rRNA profiling revealed that PHGG shifted dysbiotic microbial signatures toward fiber-responsive Bacteroidales lineages (e.g., Muribaculaceae, Alistipes, Rikenellaceae) and partially normalized community structure in beta-diversity analyses. CONCLUSION: These findings demonstrate that oligosaccharide-enriched PHGG ameliorates AD-like inflammation through concurrent modulation of cutaneous immune responses, colonic mucosal immunity, and gut microbial community structure, supporting a gut-skin axis mechanism. Future studies quantifying microbial metabolites are warranted to establish causal mediators of gut-to-skin signaling. © 2026 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.