Topical Carboxytherapy Modulates the Skin Microbiome Following <scp> CO ₂ </scp> Laser Resurfacing: A Pilot Study

Skin microbiome contributes to cutaneous homeostasis and barrier defense by regulating keratinocyte proliferation, angiogenesis, and immune responses [1, 2]. Carbon dioxide (CO2) laser resurfacing, widely used for photoaging and scar revision, induces controlled dermal injury and transient skin barrier disruption to trigger the wound healing cascade. Topical carboxytherapy, which delivers CO2 transdermally, is proposed to enhance tissue regeneration by improving oxygenation and microvascular perfusion [3]; however, its mechanistic impact on skin physiology and microbial communities remains poorly defined. Given the role of skin microbiota in wound healing and inflammation, understanding how these procedures affect microbial dynamics is clinically relevant. This pilot study aimed to characterize the facial skin microbiome following full-face CO2 fractional resurfacing and post-procedural treatment with topical carboxytherapy (CO2 Lift, Lumisque, Weston, FL). Two participants were enrolled and assigned to one of two post-laser care groups: the placebo group (n = 1) received standard care with a petroleum-based ointment, while the intervention group (n = 1) was treated with a gel-formulated carboxytherapy. VISIA-CR (Canfield Scientific Inc., Parsippany, NJ) imaging was performed at baseline and 12 weeks post-procedure (Figure 1). Microbiome samples were collected from the left versus right malar cheek at baseline and week 4 using standardized swabbing. Microbial profiling was performed via 16S rRNA gene sequencing with genus-level taxonomic assignment; sequencing depth and diversity metrics were evaluated descriptively, without statistical testing, due to the limited sample size. Genus-level taxonomic composition is shown in Figure 2. Given that only one participant was included per group, this exploratory pilot study was not powered for statistical comparison between groups, and all findings are presented as hypothesis-generating observations without inference of group differences or treatment effects. Cutibacterium spp. was the dominant genus across all subjects, with bilateral detection at both time points. Relative abundance increased from 79% at baseline to 92% at week 4. Corynebacterium spp. was the second most abundant genus (11% at baseline, 3% at week 4), followed by low-abundance taxa including Streptococcus spp. and Staphylococcus spp. Alpha diversity patterns varied between participants at baseline and over time; both groups exhibited a slight decline. These findings are reported descriptively only. Beta diversity analysis suggested overall compositional stability within individuals between baseline and follow-up, though no formal clustering or between-group comparisons can be inferred. An observed increase in the relative abundance of Cutibacterium spp., presumed to be C. acnes, following CO2 laser resurfacing may suggest a potential role in maintaining microbial balance and supporting tissue repair. As the primary commensal of sebaceous skin, C. acnes is well-adapted to lipid-rich environments and contributes to skin homeostasis through immunomodulation, lipid metabolism, and inhibition of opportunistic pathogens [4]. Reduced C. acnes diversity has been associated with aging and frailty, while its antioxidant activity and ability to suppress biofilm formation support a protective role in wound healing [1, 5]. These mechanistic interpretations are intended to contextualize the observed microbiome patterns rather than establish causality. Although limited by a small sample size, these findings indicate that neither CO2 laser resurfacing nor adjunctive topical carboxytherapy disrupts the composition or diversity of the facial skin microbiome. Given the bidirectional interaction between skin microbiota and wound regeneration, future studies should include larger cohorts and metagenomic sequencing to further define the impact of adjunctive treatments on microbial dynamics. Nonetheless, this pilot study suggests post-procedural microbiological stability and highlights the feasibility of incorporating microbiome endpoints in studies aimed at optimizing dermatologic interventions. Barbara Hernandez-Rovira: Writing-original draft (equal); formal analysis (lead); visualization. Emma Villamaria: Writing-original draft (equal); formal analysis (supporting). Julia Oh: Writing-review and editing (equal); validation. Bengisu Ozarslan: Writing-review and editing (equal); formal analysis (supporting). Saranya Wyles: Conceptualization; methodology; supervision; writing-review and editing (equal). This study was supported by Lumisque Skincare, LLC. The funder was not involved in study and manuscript preparation. AI was not used in the composition of this manuscript. This study was approved by the Mayo Clinic Institutional Review Board (IRB 23-005182). Written informed consent was obtained from all participants included in this study. The authors declare no conflicts of interest. The data that support the findings of this study are available from the corresponding author upon reasonable request.