ISOTRETINOIN AND THE HUMAN MICROBIOME: EMERGING INSIGHTS INTO SKIN AND GUT INTERACTIONS

Isotretinoin remains the most effective systemic therapy for severe acne vulgaris, yet growing evidence indicates that its therapeutic effects extend beyond sebaceous gland suppression and anti-inflammatory activity. Recent studies suggest that isotretinoin modulates both the skin and gut microbiota, influencing microbial diversity and host–microbe interactions. This narrative review summarizes current evidence published between 2017 and 2025 regarding isotretinoin’s impact on the skin and intestinal microbiota and its potential clinical implications. A structured literature search of PubMed, Scopus, Web of Science, and Google Scholar identified 28 relevant studies. The findings indicate that isotretinoin significantly reduces the abundance of Cutibacterium acnes while increasing overall microbial diversity, suggesting ecological restoration of the skin microbiome. Strain-level analyses reveal that isotretinoin selectively suppresses more virulent C. acnes phylogroups while promoting the persistence of commensal strains. Evidence from animal and clinical studies also points to mild, reversible changes in the gut microbiota, possibly mediated through systemic immune and metabolic pathways. Although concerns about isotretinoin-induced dysbiosis or inflammatory bowel disease remain largely unsupported, its systemic effects on microbial ecosystems warrant further investigation. Overall, isotretinoin should be regarded not only as a cornerstone acne therapy but also as a microbiome-modulating agent that may pave the way for more personalized and biologically informed dermatologic care.