The Emerging Role of Probiotics, Postbiotics and Microbiome-Derived Compounds in Melasma: A Scoping Review

Introduction: Melasma is a chronic acquired hyperpigmentation disorder with a multifactorial pathogenesis involving ultraviolet (UV) radiation, hormonal influences, oxidative stress, inflammation, and dysregulated melanogenesis. Emerging evidence suggests that the gut–skin axis and microbiome-targeted interventions, including probiotics, postbiotics, and microbiome-derived compounds, may modulate biological pathways relevant to melasma. However, the available evidence remains heterogeneous and has not been comprehensively mapped. Objective: To map and synthesize the existing evidence on probiotics, postbiotics, and microbiome-derived compounds as potential therapeutic approaches for melasma and to summarize the proposed biological mechanisms underlying their effects. Methods: A scoping review was conducted according to the JBI methodology and reported following the PRISMA-ScR guidelines. MEDLINE (PubMed), Embase, and Scopus were searched for English-language studies published between January 2011 and October 2025. Eligible studies included clinical trials, animal studies, and in vitro investigations evaluating probiotics, postbiotics, synbiotics, or microbiome-derived compounds in relation to melasma, melanogenesis, oxidative stress, or pigmentation-related pathways. Two reviewers independently screened studies, extracted data, and synthesized findings descriptively. Results: Seventeen studies met the inclusion criteria, including three clinical trials, one animal study, three combined in vitro/in vivo studies, and ten in vitro studies. Clinical evidence suggested that oral probiotic-based interventions may reduce melasma severity and mitigate UV-induced skin damage; however, two of the three trials evaluated probiotics combined with carotenoids, limiting attribution of benefits to probiotics alone. Experimental studies consistently demonstrated anti-melanogenic effects through inhibition of tyrosinase activity, downregulation of microphthalmia-associated transcription factor (MITF), and modulation of ERK, PI3K/AKT, PKA/CREB, and MEK/ERK signaling pathways. Additional mechanisms included antioxidant activity, attenuation of UV-induced oxidative stress, immunomodulatory effects, and regulation of inflammatory mediators. One observational study also suggested a potential association between gut microbiota alterations and melasma, supporting a plausible role for the gut–skin axis, although causal evidence remains lacking. Conclusions: Current evidence suggests that probiotics, postbiotics, and microbiome-derived compounds may influence biological pathways implicated in melasma pathogenesis through anti-melanogenic, antioxidant, anti-inflammatory, and photoprotective mechanisms. Nevertheless, the evidence is predominantly preclinical, and clinical data remain limited and heterogeneous. Well-designed randomized controlled trials evaluating probiotic strains as standalone interventions, with mechanistic outcome measures and long-term follow-up, are needed before these approaches can be recommended as evidence-based adjunctive therapies for melasma.