Scalp Microbiota Dysbiosis in Seborrheic Alopecia and Restoration Following Herbal Extract Shampoo Intervention

Seborrheic alopecia (SA) is one of the most common forms of hair loss with a complex pathogenesis involving multiple etiological factors. Although the scalp microbiome has been implicated in various scalp disorders, its specific role in the development and progression of SA remains incompletely understood. To characterize the scalp microbiome in SA, we performed high-throughput sequencing of the 16S rRNA gene and ITS region on scalp samples from 41 Chinese SA participants before and after a 12-week intervention with a shampoo containing herbal extracts (ginger root, Polygonum multiflorum, and Platycladus orientalis leaf) and 29 healthy controls. The untreated SA group exhibited significant microbial dysbiosis compared to the healthy controls, characterized by reduced bacterial and fungal alpha diversity and increased relative abundances of Staphylococcus, Cutibacterium, and Malassezia. LEfSe analysis confirmed the significant enrichment of these three genera. Correlation network analysis revealed a substantial restructuring of microbial interactions in the untreated SA group: Staphylococcus and Malassezia lost all positive correlations with other genera, whereas Cutibacterium displayed relatively stable topological relationships. Following the 12-week intervention, the treated SA group showed significant clinical improvement (reduced hair loss and scalp sebum content), along with a restoration of microbial diversity to levels comparable to the healthy group and a normalization of the abundances of Staphylococcus and Malassezia. Our study confirms the critical role of scalp microecological dysbiosis in SA pathogenesis and identifies Staphylococcus and Malassezia as key taxa strongly associated with this dysbiosis. These findings provide a theoretical foundation for developing microbiome-targeted strategies for SA treatment and support the use of multi-targeted, plant-based interventions to restore microbial homeostasis and promote hair growth.