Background: Overweight and obesity have become public health problems worldwide. An increasing number of research works are focusing on skin physiology and the manifestations of obesity-associated skin diseases, but little is known about the correlations between body mass index (BMI), facial skin physiological parameters, and the facial skin microbiome in healthy women. Objective: To investigate the correlations between BMI, facial skin physiological parameters and facial bacteria and fungi in 198 women aged 18 to 35 years in Shanghai. Methods: According to the international BMI standard and Chinese reference standard, subjects were divided into three groups, “lean” B1, “normal” B2 and “overweight” B3, and the physiological parameters of facial skin were measured by non-invasive instrumental methods, and the skin microbiota was analyzed by 16S rRNA and ITS high-throughput sequencing. Results: Compared with the skin physiological parameters of the normal group, those of the overweight group exhibited a significant increase in trans-epidermal water loss (TEWL), which indicated that the skin barrier was impaired. The skin haemoglobin content was significantly increased, and skin surface pH was significant decreased in those with a high BMI. Furthermore, α-diversity, analysed using the Shannon, Chao, Sobs, and Ace indexes, was increased in the overweight group, suggesting that the diversity and species abundance of facial bacterial and fungal microbiota were also increased. Moreover, the overweight group had higher abundances of Streptococcus, Corynebacterium, Malassezia, and Candida. Notably, skin surface pH was significantly and negatively correlated with the relative abundances of Malassezia, Candida, and Cladosporium. Besides, the abundance of Malassezia was positively associated with the abundances of Staphylococcus and Corynebacterium. Conclusion: These results indicate that BMI is associated with differences in the biophysical properties and microbiome of the facial skin. A high BMI affects the integrity of skin barrier and changes the skin flora diversity and species composition.

Objective: Oxidative stress activates the reactive oxygen species (ROS) and excessive ROS can damage skin cells, initiating oxidative stress responses that contribute to inflammation, aging, and other skin issues. As a resident skin bacterium, Cutibacterium acnes (C. acnes) plays an important role in maintaining skin homeostasis and provides antioxidant benefits. However, the metabolite components and mechanisms of C. acnes exerting antioxidant activity are not yet clear. This study aimed to analyze the potential antioxidant effects of C. acnes cell‐free supernatant and the mechanisms.Methods: The antioxidant effects were evaluated by measuring the scavenging activities of 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH), 2,2′‐azinobis (3‐ethylbenzothiazoline‐6‐sulfonic acid ammonium salt) (ABTS) radicals, and hydroxyl radicals, as well as the effects on ROS levels in menadione‐induced primary human keratinocytes in vitro. Additionally, western blot analysis was performed to assess the antioxidant effects of the C. acnes CCSM0331 cell‐free supernatant (CFS).Results: C. acnes CCSM0331 was isolated from the facial skin of healthy individuals. This strain, classified as type II, is associated with healthy skin. The CFS of strain CCSM0331 contained various short‐chain fatty acids (SCFAs), glutathione peroxidase (GSH‐Px), and total superoxide dismutase(T‐SOD), exhibiting strong DPPH and ABTS radical scavenging capabilities, thus demonstrating substantial antioxidant activity. In a reactive oxygen species model induced by menadione in primary human keratinocytes, the addition of 5% of the fermentation supernatant from this strain significantly reduced ROS levels, indicating a notable ROS‐scavenging effect. Western blot analysis further confirmed that the CCSM0331 fermentation supernatant activated the expression of Nrf‐2 and HO‐1 proteins, thereby activating the Nrf‐2 oxidative stress pathway and exerting antioxidant effects.Conclusion: C. acnes CCSM0331 is a promising skin probiotic with notable antioxidant properties. The activity of this strain exhibited significant free radical scavenging activity, suggesting its potential application in the development of antiaging products. This study provides theoretical support for the screening of functional skin bacteria or skin probiotics.

Ultraviolet B (UVB) radiation is a major environmental stressor that induces oxidative stress, inflammation, and skin barrier dysfunction. Although Staphylococcus epidermidis ( S. epidermidis ) is a beneficial skin commensal, current evidence on its protective effects against UVB-induced skin damage has primarily focused on reference strains or a limited number of individual metabolites. The broader photoprotective potential of postbiotics derived from newly isolated skin commensal strains remains insufficiently characterized. Here, we investigated the anti-photodamage activity and underlying mechanisms of the cell-free supernatant of S. epidermidis CCSM0287 (SE 287-CFS), a multifunctional skin commensal isolated from healthy skin, in UVB-induced HaCaT cells. SE 287-CFS significantly reduced intracellular reactive oxygen species (ROS), malondialdehyde (MDA), and pro-inflammatory cytokines, while enhancing antioxidant enzyme activity and interleukin-10 (IL-10) secretion. Mechanistically, SE 287-CFS inhibited p65 nuclear translocation and suppressed activation of the ROS/MAPK/NF-κB signaling pathway. In addition, SE 287-CFS increased transepithelial electrical resistance (TEER) and promoted keratinocyte proliferation and migration, indicating improved skin barrier function. Non-targeted metabolomics combined with correlation analysis suggested that butyric and adipic acids were primarily associated with antioxidative and anti-inflammatory effects. Other organic acids, including succinic, acetic, and propanoic acids, may contribute to skin barrier repair. Together, this study demonstrates that SE 287-CFS protects against UVB-induced photodamage by modulating oxidative stress, suppressing inflammation, and improving skin barrier function. It also highlights the potential of postbiotics derived from skin commensals as candidates for microbiome-based skin photoprotection. IMPORTANCE: Staphylococcus epidermidis is a dominant commensal skin bacterium that plays a crucial role in maintaining skin homeostasis and defending against various external stressors. UV radiation is a primary environmental factor that induces oxidative stress and inflammatory responses, resulting in photodamage and impaired skin barrier function. This study demonstrated the significant protective effect of SE 287-CFS in counteracting ultraviolet B (UVB)-induced skin damage. By modulating the reactive oxygen species (ROS)/MAPK/NF-κB signaling pathways, SE 287-CFS effectively alleviated oxidative stress, reduced inflammatory cytokine production, and enhanced skin barrier function. This research highlighted the potential of using skin commensal bacteria as a novel therapeutic strategy to enhance skin protection against UVB-induced damage, providing a promising approach to improve skin health under environmental stressors like UV radiation.

Aims: Phenoxyethanol is a broad-spectrum antimicrobial agent widely used in cosmetic formulations. However, its antibacterial effects on different skin bacteria, particularly the predominant Cutibacterium acnes and its various phylotypes, remain unclear. The objective of this study was to examine the antimicrobial effects of phenoxyethanol on C. acnes and explore the mechanism. Methods and results: Phenoxyethanol exhibited strong antimicrobial effects against both C. acnes ATCC6919 (phylotype IA1) and CCSM0331 (phylotype II), achieving a minimum inhibitory concentration (MIC) of 0.5% (v/v). Sub-MIC concentrations showed a stronger inhibitory effect on CCSM0331. RNA-seq and metabolomic analyses revealed that phenoxyethanol disrupted cell membrane integrity and influenced essential metabolic pathways, such as energy metabolism, amino acid metabolism, and pyrimidine metabolism. Additionally, glycolysis and the Wood-Werkman cycle were inhibited in CCSM0331 but enhanced in ATCC6919. The expression of genes involved in porphyrin metabolism, associated with inflammation, was significantly reduced. Conclusions: Phenoxyethanol exhibits the antimicrobial activity against C. acnes, with differential effects on phylotypes, targeting critical metabolic pathways and cellular processes. These findings indicate its potential for acne treatment.