Microbiome and Skin Health: A Systematic Review of Nutraceutical Interventions, Disease Severity, Inflammation, and Gut Microbiota.

Skin disorders are a major global cause of morbidities, and increasing evidence links several to gut microbiome dysregulation. Because of this the bidirectional gut-skin axis, nutraceuticals have been proposed as therapeutic adjuncts, but their clinical effects across skin conditions remain unclear. To understand how pro/pre/synbiotics can affect health, we conducted a systematic review to investigate disease severity indices, inflammatory and immunological markers, quality of life, and changes in gut microbiota composition. PubMed, Embase, and Web of Science were utilized to identify relevant randomized clinical trials. Selected articles were pre-piloted for in-depth analysis and data extraction. We included 60 randomized controlled trials involving human participants with 5 dermatological conditions, including atopic dermatitis, psoriasis, acne vulgaris, chronic urticaria, and melasma, treated with probiotics, prebiotics, or synbiotics. Risk of bias was generally low across trials, with some having concerns. The SCORAD of the treated group was substantially lower than that of the placebo group in 30 of the 47 trials on atopic dermatitis. Inflammatory markers showed a range of results; some showed significant changes, while others produced contradictory results. Five trials that examined atopic dermatitis and psoriasis independently showed a significant improvement in Quality of Life. The PASI score was considerably lower in psoriasis in three of the five RCTs. Acne vulgaris, melasma, and chronic urticaria were not well documented. Major limitations included heterogeneity in interventions and outcomes, small sample sizes, and inconsistent reporting of microbiome analyses. Nutraceuticals show potential as additional treatments, but further, large scale studies are required.