SKIN microbiota may influence how human skin responds to ultraviolet radiation (UVR), with a small study finding that their presence was associated with greater keratinocyte apoptosis and inflammatory cell infiltration following exposure.
The influence of skin microbiota on the response to UVR remains incompletely understood, despite both being regular features of the skin environment. Researchers investigated whether the healthy skin microbiota influenced UVR-induced inflammation, or the sunburn response, in 10 healthy volunteers with Fitzpatrick skin types I–III.
Upper back skin was either disinfected with ethanol or left untreated before participants were exposed to a range of solar-simulated UVR doses. Erythema was assessed 24 hours after exposure, while skin biopsies were collected before exposure and at 0.5 and 24 hours afterwards.
Disinfected and non-disinfected skin had similar minimal erythema doses, with no significant differences in the UVR erythema dose-response. At 0.5 hours after exposure, the two groups also showed similar responses across the measured parameters.
However, differences became apparent at 24 hours. Disinfected skin had significantly fewer TUNEL-positive keratinocytes, indicating reduced apoptosis, alongside fewer CD68-positive macrophages and neutrophil elastase-positive neutrophils. These differences were accompanied by increased Ki67-positive keratinocyte proliferation.
The findings were supported by spatial transcriptomic analysis. Proliferation-associated genes and pathways were upregulated in disinfected skin, while apoptosis- and inflammation-associated pathways were enriched in non-disinfected skin.
The findings suggest that the healthy skin microbiota may modulate the response to UVR rather than altering the initial threshold for erythema. In the study, microbiota presence was associated with greater keratinocyte apoptosis and infiltration of neutrophils and macrophages, alongside reduced keratinocyte proliferation.
The authors noted that these findings indicate a potential role for the skin microbiota in regulating cellular responses following UVR exposure. Further research will be needed to clarify the mechanisms involved and determine how these interactions may contribute to human skin health.
Reference
Duan W et al. Commensal skin microbiota modulate responses to ultraviolet radiation in humans. Br J Dermatol. 2026;DOI:10.1093/bjd/ljag334.
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