Topical microbiome-based cosmetics (probiotics, postbiotics, prebiotics) for skin barrier and appearance in healthy and sensitive-skin adults: a systematic review and meta-analysis
Year: 2026
Type: preprint
Study design: Study Protocol
Abstract: Background. Topical microbiome-based cosmetics containing live probiotics, postbiotics (heat-killed/paraprobiotics), and prebiotics are widely marketed for improving skin barrier function and appearance, yet the published evidence in healthy and sensitive-skin adults is fragmented and methodologically heterogeneous. No pre-registered pooled synthesis currently exists for this population and route of administration. Objectives. To systematically evaluate the efficacy and safety of topical microbiome-based cosmetics versus placebo/vehicle in healthy adults and adults with sensitive skin, using a pre-registered protocol. Methods. We will search PubMed, Embase (Ovid), Web of Science, Cochrane CENTRAL, and CNKI from inception to the search date. Randomized controlled trials (RCTs) of topical (non-ingested) application in healthy adults or those with sensitive skin will be included; studies in atopic dermatitis, acne vulgaris, rosacea, other inflammatory/infectious dermatoses, wounds, or pregnancy/lactation will be excluded. Primary outcomes: transepidermal water loss (TEWL, g/m²·h), stratum corneum hydration (Corneometer AU/%), skin elasticity (Cutometer), erythema (Mexameter EI / CIELAB a*), and melanin. Secondary/exploratory: sensitive-skin measures (lactic acid sting test / sensory score) and skin microbiome composition. Two reviewers will screen and extract data independently (Rayyan), with a third arbitrating. Risk of bias will be assessed with Cochrane RoB 2. We will use random-effects models (DerSimonian–Laird); meta-analyze same-scale continuous outcomes with MD and different-scale with SMD; dichotomous outcomes with OR; assess heterogeneity with I²; and rate certainty with GRADE. Missing change scores will be derived from baseline/endpoint SDs assuming a correlation of 0.5. Skin microbiome outcomes will be synthesized narratively/qualitatively (route B); a single-taxon MD sub-pool will be performed only if ≥2 homogeneous studies (same taxon + same unit) are identified. Expected outcomes. A transparent, pre-registered estimate of the effects of topical microbiome-based cosmetics on objective skin barrier and appearance endpoints in healthy/sensitive-skin adults, clarifying where evidence is sufficient for pooling versus where only narrative synthesis is feasible.
Author: wanglejian
Language: English
Subfield: Food Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7204021672