The Rosacea Research Digest from the National Rosacea Society keeps you up to date on recently published basic and clinical research on rosacea, as well as news, reviews, and presentations. It goes out on the last weekday of each month.

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Research

Integrative analysis of fungal and bacterial microbiomes across skin, blood, and stool in rosacea patients.

Joura MI, Nemes-Nikodém É, Jobbágy A, et al. Int J Mol Sci. 2025; 26(17):8127. DOI: 10.3390/ijms26178127

Rosacea is a chronic inflammatory skin disorder with multifactorial pathogenesis involving immune dysregulation and microbial alterations. This study compared the mycobiomes of skin, blood, and stool samples in rosacea patients and healthy controls to assess fungal diversity, abundance, and possible translocation, as well as associations with bacterial microbiomes. Internal transcribed spacer (ITS) region sequencing was performed on samples from 14 rosacea patients and 8 controls. While distinct fungal community compositions were observed across sample types, no significant differences in fungal diversity or genus abundance were found between the patient and control groups in any compartment. Malassezia dominated the skin mycobiome, while stool samples showed higher abundances of Candida and Saccharomyces, which were inversely correlated. Patients with high skin and blood Malassezia also exhibited increased Cutibacterium abundance, suggesting a potential role in impaired skin barrier integrity. Stool samples with elevated Saccharomyces correlated with higher levels of anti-inflammatory bacteria Prevotella and Agathobacter, whereas Candida dominance showed the opposite. These findings suggest that fungal dysbiosis, in the interplay with bacterial communities, may influence rosacea pathogenesis through the gut–skin axis. This work underscores the significance of integrated microbiome research across multiple biological compartments in order to enhance our understanding and potential targeting of microbial factors in rosacea.

Exploring the risk factors of rosacea exacerbation associated with COVID-19 infection or vaccination: a cross-sectional study.

Yin X, Zhao Y, Zhou L, et al. Acta Derm Venereol. 2025 Sep 4;105:adv43615. DOI: 10.2340/actadv.v105.43615. PMID: 40908756.

COVID-19 can affect the skin, with rosacea flare-ups reported after infection or vaccination. This study compared rosacea patients with and without post-COVID-19 exacerbation to identify contributing factors. A customized electronic questionnaire was administered to rosacea patients, gathering COVID-19 infection/vaccination status, demographics, and rosacea features. Participants were classified by post-COVID-19 rosacea exacerbation vs none. Multivariable logistic regression identified risk factors. Finally, a total of 104 patients were analysed; 15.4% experienced rosacea exacerbation after COVID-19 vaccination and 28.8% after infection. Comorbidities such as metabolic diseases or allergic diseases were associated with a higher risk of rosacea exacerbation after vaccination or infection (OR = 11.083, 95% CI: 1.136-108.135). Burning and stinging symptoms predicted higher exacerbation risk after vaccination (OR = 8.978, 95% CI 1.968-40.969). Papulopustular rosacea was associated with lower risk (OR = 0.276, 95% CI: 0.066-1.160). Higher body mass index (BMI) was associated with lower exacerbation risk after vaccination (OR = 0.646, 95% CI 0.450-0.928) and infection (OR = 0.731, 95% CI: 0.572-0.933). Frequent rosacea episodes increased exacerbation risk after infection (OR = 8.288, 95% CI: 2.044-33.608). In conclusion, lower BMI was associated with higher risk of rosacea exacerbation after COVID-19 vaccination or infection. Patients with burning and stinging symptoms or a non-papulopustular subtype were more likely to experience exacerbation after vaccination.

No causal relationship between Helicobacter pylori infection and rosacea: a 2-sample Mendelian randomization study.

Qiu Y, Shen S, Zhang Y. Clin Cosmet Investig Dermatol. 2025 Sep 12;18:2359-2365. doi: 10.2147/CCID.S543236. PMID: 40963887; PMCID: PMC12439818.

Background: Previous studies have shown that patients with rosacea have a higher prevalence of Helicobacter pylori (H. pylori) infection. However, whether H. pylori infection contributes to the development of rosacea remains unclear, and no genetic association studies between the two have been conducted to date. Genome-wide association studies (GWAS) database is a public resource that stores and shares data that aims to identify genetic links to complex diseases, physiological traits, or drug responses. Mendelian randomization (MR) is an epidemiological approach to investigate the effect of the exposure on a specific outcome. Due to the random assortment of single nucleotide polymorphisms (SNPs), they are less likely to be influenced by confounding factors. The MR design can mitigate residual confounding and reverse causation, strengthening the causal inference of the exposure's association with the outcome. Methods: We use GWAS database and MR design to assess the causal relationship between H. pylori infection and rosacea. Inverse variance weighted (IVW) was the main method in this study, along with MR Egger, simple mode, weighted median, and weighted mode. GWAS data for H. pylori infection and rosacea were retrieved from the Medical Research Council Integrative Epidemiology Unit (MRC-IEU) Open GWAS, GWAS catalog and FinnGen database. Results: We used H. pylori infection as exposure data and rosacea as outcome data, and all p-values in MR analysis were all greater than 0.05. These conclusions were confirmed by sensitivity analysis. Conclusion: Our MR analysis provides no evidence of a causal relationship between H. pylori infection and rosacea. This indicates that patients with rosacea may not need routine testing for H. pylori infection and routine eradication of H. pylori may not benefit rosacea patients.