Common Misconceptions About the Skin Microbiome
The skin microbiome is a complex ecosystem, but research into its role in conditions like atopic dermatitis and rosacea is often misrepresented. This article examines what clinical studies actually measure.
What is the skin microbiome?
The skin microbiome is the collection of microorganisms—bacteria, fungi, viruses, and mites—that reside on the skin. It is also referred to as the skin microbiota or skin flora. Research into the skin microbiome is a rapidly evolving field, but it is not a single entity; its composition varies by body site, age, and health status. The evidence base for many claims about the microbiome comes from observational studies and clinical trials that measure specific markers, not from direct manipulation of the microbiome in humans.
One pathway that has been a focus of research is the relationship between skin barrier integrity and inflammation. Studies have investigated how skin barrier function and the skin microbiome change in response to topical moisturizers in older adults [3], and how topical ivermectin affects protease activity, antimicrobial peptide expression, and the skin microbiome in rosacea [4].
Research Studies
Vernix caseosa and atopic dermatitis prevention in newborns
Vernix caseosa is a naturally occurring, white, creamy substance that covers the skin of newborns at birth. It forms during the last trimester of pregnancy. A clinical trial is investigating whether retention of vernix caseosa in newborns can serve as a primary prevention strategy for atopic dermatitis (AD), also known as eczema [1]. AD is a common chronic inflammatory skin disease that usually begins in infancy and causes significant itching, discomfort, and sleep disturbance. It affects up to one in five children worldwide. Research has shown that genetic and environmental factors contribute to its development, especially those related to skin-barrier integrity and the skin microbiome during early life [1]. This study is ongoing; no results are available yet.
Skin barrier function and inflammation in aging: the BIA study
A randomized, investigator-blinded, self-controlled pilot study is examining the physiologic response to topical moisturizers among older adults with dry skin [3]. The overarching hypothesis is that skin barrier decline is an important source of chronic inflammation, and that skin barrier restoration with moisturizers can reduce serum biomarkers of inflammation. The primary objective is to determine the feasibility for a larger trial. Secondary objectives include determining the extent to which measures of serum inflammation, skin barrier function, and the skin microbiome change in response to moisturizers. Participants apply one of two topical moisturizers that are widely available [3]. This study is ongoing; no results are available yet.
Topical ivermectin and rosacea-specific inflammation
A single-site, 16-week open-label study at the University of California, San Diego, is assessing the role of topical ivermectin 1% cream and its effect on protease and antimicrobial peptide expression and on the skin microbiome in rosacea [4]. The investigators measure serine protease activity and cathelicidin and skin microbiome of all subjects before treatment. All subjects receive ivermectin topical cream and are instructed to apply it daily for 12 weeks. Participants return for monthly visits during which their clinical symptoms of facial redness and number of facial papules are scored [4]. This study is ongoing; no results are available yet.
Lymphedema and inflammatory markers
An observational, cross-sectional study aims to characterize the biological profile of primary and secondary lymphedema by investigating five interconnected biological domains: T helper 2 (Th2)-related inflammation, endothelial activation, metabolic dysfunction, lymphatic biology, and tissue fibrosis [2]. Lymphedema is traditionally considered a disorder of impaired lymphatic drainage resulting in the accumulation of interstitial fluid. However, increasing evidence suggests that its development and progression involve chronic inflammation, endothelial dysfunction, metabolic alterations, abnormal lymphatic signaling, adipose tissue accumulation, and progressive tissue fibrosis [2]. While these mechanisms are not directly about the skin microbiome, they illustrate the complexity of skin-related conditions and the need for rigorous research. This study is ongoing; no results are available yet.
Comparing study designs
The table below summarizes key features of the studies discussed above.
| Study | Condition | Intervention/Exposure | Primary Outcome | Status |
|---|---|---|---|---|
| NCT07333378 [1] | Atopic dermatitis | Retention of vernix caseosa | Primary prevention of AD | Ongoing |
| NCT06750653 [3] | Dry skin in older adults | Topical moisturizers | Feasibility; serum inflammation, skin barrier, microbiome | Ongoing |
| NCT02806414 [4] | Rosacea | Topical ivermectin 1% cream | Protease activity, cathelicidin, skin microbiome | Ongoing |
| NCT07770399 [2] | Lymphedema | Observational | Biological profile (Th2 inflammation, etc.) | Ongoing |
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Sources
- [1] Retention of Vernix Caseosa in Newborns for Primary Prevention of Atopic Dermatitis
- [2] Biological Profile of Primary and Secondary Lymphedema: Inflammatory, Endothelial, Metabolic, Lymphatic, and Fibrotic Markers
- [3] Skin Barrier Function and Inflammation in Aging: The BIA Study
- [4] Evaluation of the Inhibitory Effects of Topical Ivermectin on Markers of Rosacea Specific Inflammation.