Rosacea, microbiome and probiotics: the gut-skin axis

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TL;DR

This narrative review explores the role of the gut-skin axis in rosacea, highlighting that both skin and gut microbiota dysbiosis contribute to its pathophysiology. The paper summarizes evidence that rosacea patients show altered skin microbiota (e.g., increased Demodex mites, Corynebacterium kroppenstedtii) and gut microbiota (e.g., decreased Prevotella, increased Bacteroides), and that probiotic supplementation may improve clinical outcomes. The clinical significance lies in identifying the microbiome as a potential therapeutic target for rosacea, though more research is needed.

Full summary

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**Background** Rosacea is a chronic inflammatory skin disease affecting approximately 5.5% of the general population, primarily patients aged 45–60 years. It presents with persistent erythema, papules, pustules, telangiectasia, flushing, and phyma, and over 50% of patients have ocular involvement. The pathophysiology involves an unbalanced immune system, vascular and neural dysfunction, and microbial triggers. The gut-skin axis describes bidirectional interactions between gut and skin microbiota, but its role in rosacea is less explored than in atopic dermatitis or psoriasis. This narrative review aims to analyze the role of skin and gut microbiota in rosacea pathophysiology and the potential of probiotics as a therapeutic target.

**Methods** This is a narrative review summarizing current literature on rosacea pathophysiology, skin and gut microbiota composition in rosacea patients, and probiotic interventions. The authors synthesized findings from studies using next-generation sequencing (NGS) of the 16S rRNA gene, case-control studies, cohort studies, and clinical trials. Key studies reviewed include those by Zaidi et al. (2018), Rainer et al. (2020), Thompson et al. (2020, 2021), Woo et al. (2020), Wang et al. (2020), Murillo et al. (2014a), Nam et al. (2018), Chen et al. (2021), and Moreno-Arrones et al. (2021). Probiotic trials included Manzhalii et al. (2016), Buianova et al. (2018), and Berardesca et al. (2023).

**Key Results** - **Skin microbiota**: Studies show contradictory results on alpha-diversity differences between rosacea patients and controls. Zaidi et al. found no significant difference in Shannon index between monozygotic twins with and without rosacea. Rainer et al. reported greater richness in rosacea patients but not statistically significant. Wang et al. observed increased alpha-diversity in papulopustular rosacea (PPR) patients. At the phylum level, Actinobacteria was dominant in rosacea patients (Thompson et al., 2021), while Firmicutes increased in erythematotelangiectatic rosacea (ETR) and Actinobacteria decreased in PPR (Wang et al., 2020). Key species differences include increased Corynebacterium kroppenstedtii in rosacea patients (6% in those aged 40–49 vs. virtual absence in controls; Rainer et al., 2020), increased Campylobacter ureolyticus and Prevotella intermedia in PPR (Thompson et al., 2020), and decreased Cutibacterium acnes in rosacea (Wang et al., 2020). Demodex mite density is significantly higher in rosacea patients (71.0 mites/cm² vs. 8.7 mites/cm² in controls; Chang and Huang, 2017). - **Gut microbiota**: Nam et al. (2018) found increased Acidaminococcus and Megasphaera and decreased Peptococcaceae and Methanobrevibacter in rosacea patients. Chen et al. (2021) reported higher Bacteroides and Fusobacterium and lower Prevotella and Sutterella. Moreno-Arrones et al. (2021) identified decreased Prevotella copri and increased Akkermansia muciniphila and Parabacteroides distasonis in PPR patients. - **Probiotic interventions**: Manzhalii et al. (2016) reported that 32% of patients receiving Escherichia coli Nissle 1917 plus standard therapy showed recovery vs. 17% in controls. Buianova et al. (2018) found 57% complete remission with Bifidobacterium plus polyoxidonium vs. 28% with standard therapy. Berardesca et al. (2023) showed that topical M89PF (containing Vitreoscilla filiformis extract) improved skin hydration, reduced transepidermal water loss (TEWL), decreased Demodex density, and improved erythema.

**Clinical Implications** The gut-skin axis plays a significant role in rosacea pathophysiology, with both skin and gut microbiota dysbiosis contributing to inflammation and symptom severity. Current treatments often fail to achieve complete remission, and probiotics offer a promising adjunctive therapy. However, evidence is limited to small trials and case reports. Larger, well-designed randomized controlled trials are needed to establish efficacy and optimal strains. Modulation of the microbiome, either through oral probiotics or topical postbiotics, could improve clinical outcomes and quality of life in rosacea patients.