It is well established that differences in the microbiome — the ecological community of microorganisms that live within and on the human body — plays a role in the development of rosacea and affect the severity of signs and symptoms. Research shows that rosacea patients often suffer from an overgrowth of Demodex mites, a natural inhabitant of the skin of nearly every human, and mounting evidence points to an imbalance of bacteria in both the skin and gut microbiome as influencing the development and severity of rosacea signs and symptoms.1 However, a new study has focused on an overlooked portion of the microbiome that may also be involved in rosacea’s development: yeasts and other fungi.2
A team of researchers in Budapest, Hungary collected skin, stool and blood samples from 14 rosacea patients and eight healthy control subjects, and performed genetic analysis on the samples to identify the bacterial and fungal species present in each. Blood samples were included to examine whether the bloodstream might be an avenue for changes in the gut microbiome to be transmitted to the skin.
The researchers noted that certain fungi in the microbiome (known as the “mycobiome”) have been shown to contribute to immune response, inflammation and skin barrier disruption in eczema and seborrheic dermatitis.3 Changes in the variety and abundance of yeasts in the genus Malassezia appear to be involved. However, a previous study found no differences in the mycobiome of rosacea patients compared to those with healthy skin.4
The new analysis also found no significant differences in terms of abundance or diversity of fungi in the skin, stool or blood samples between the rosacea patients and healthy controls. However, the investigators did find that among the rosacea patients, fungi from five genera were present in significantly higher abundances in the skin samples than in stool or blood samples, with Malassezia species being the overwhelming majority. The stool samples of rosacea patients had significantly greater abundances from nine genera, especially Candida and Saccharomyces, compared to the skin and blood samples.
Although the skin of all study participants had high levels of Malassezia, only some subjects also had high levels of the yeast in their bloodstream, and this group had significantly higher levels of Cutibacterium on their skin. The investigators noted that some strains of Cutibacterium acnes have been found to contribute to an impaired skin barrier, which can lead to inflammation.
In the stool samples of rosacea patients, Candida was found at higher levels and Saccharomyces at lower levels compared to healthy controls. These fungi also exhibited relationships with bacteria: in subjects with higher Saccharomyces levels, Prevotella and Agathobacter species, which offer anti-inflammatory benefits, were significantly more abundant. These beneficial bacteria were also more abundant in subjects with low levels of Candida.
The researchers concluded that imbalances in the mycobiome may contribute to the development of rosacea, and further study into the relationships between fungi and bacteria in the microbiome is needed.
References:
1. Asees A, Sadur A, Choudhary S. The Skin Microbiome in Rosacea: Mechanisms, Gut-Skin Interactions, and Therapeutic Implications. Cutis 2025 Jul;116(1):20-23. doi: 10.12788/cutis.1240. PMID: 40875939.
2. Joura MI, Nemes-Nikodém É, Jobbágy A, et al. Integrative Analysis of Fungal and Bacterial Microbiomes Across Skin, Blood, and Stool in Rosacea Patients. Int J Mol Sci 2025 Aug 22;26(17):8127. doi: 10.3390/ijms26178127. PMID: 40943051; PMCID: PMC12428464.
3. Jung, W.H. Alteration in skin mycobiome due to atopic dermatitis and seborrheic dermatitis. Biophys Rev 2023, 4, 011309.
4. Wang R, Farhat M, Na J, et al. Bacterial and fungal microbiome characterization in patients with rosacea and healthy controls. Br J Dermatol 2020, 183, 1112–1114.
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