Biotics for Acne-Prone Skin and Scalp Disorders: A Scoping Review

Background/Objectives: The skin microbiome maintains barrier integrity, immune homeostasis, and pathogen defense; dysbiosis contributes to acne vulgaris, dandruff, seborrheic dermatitis, atopic dermatitis, psoriasis, and alopecia. This scoping review critically appraised evidence on prebiotics, probiotics, synbiotics, postbiotics, and paraprobiotics in dermo-cosmetics for acne vulgaris and scalp disorders. Methods: A scoping search (2006–2026) covered SciELO, PubMed/PMC, Google Scholar, CAPES Portal, Scopus, Heliyon, Frontiers, Nature, Wiley, and MDPI, following PRISMA 2020 guidelines. Results: Of 1665 records, 66 were included. For acne, effective prebiotics included blackcurrant, grape seed, ginseng, trehalose, and glucomannan hydrolysate; effective probiotic strains included Streptococcus thermophilus, Bifidobacterium longum, Staphylococcus epidermidis, and Streptococcus salivarius. A synbiotic (B. breve BR03, Lacticaseibacillus casei LC03, Ligilactobacillus salivarius LS03) reduced inflammatory lesions by 56.67% in an 8-week RCT (n = 114). For scalp disorders, oral Lacticaseibacillus paracasei ST11 reduced dandruff by 70% vs. 23% (placebo); Lactiplantibacillus plantarum TCI999 increased hair root diameter (n = 50, 12 weeks); a Lacticaseibacillus rhamnosus plus Bifidobacterium longum mixture improved alopecia areata by 56% vs. 30% (n = 26, 24 weeks). Conclusions: Biotic dermo-cosmetics can modulate the cutaneous microbiome and attenuate inflammation in acne and scalp disorders, with strongest evidence for multi-strain/synbiotic formulations. Formulation stability, strain specificity, regulatory heterogeneity, and lack of standardized microbiological endpoints remain key challenges; larger standardized RCTs with active comparators are needed.