Cutibacterium acnes in Atopic Dermatitis: Roles and Potential Therapeutic Applications

Atopic dermatitis (AD) is a chronic relapsing inflammatory skin disease. Skin microbiota disorder, skin barrier dysfunction, and predominantly elevated type 2 immune responses are core initiate mechanisms of AD. Cutibacterium acnes ( C. acnes ) is a commensal bacterium that is ubiquitous and predominant in healthy skin, with intraspecific subtype diversity. The abundance of C. acnes is closely related to the sebum secreted by sebaceous glands. C. acnes has long been considered a pro-inflammatory skin bacteria that drives the development of acne vulgaris. Growing evidence supports C. acnes promotes the skin microbiota homeostasis and skin barrier maintenance, while the potential role of C. acnes in AD remains largely unexamined. This review provides the latest information on the distribution of C. acnes and its phylotypes in healthy skin and AD, meanwhile offering an overview of the possible role of C. acnes in the pathophysiological pathways underlying AD. Additionally, the review focuses on new evidence regarding the protective functions of C. acnes and its metabolites in AD, with the potential for therapeutic applications.