Which microbes lives in and on your skin?

The resident and transient microbes of the skin microbiome - drawing by Marcelline Goyen

By Marcelline Goyen, BSc

Therapist, Skin-Gut Axis Specialist & Author

Published on: July 8, 2024

Skin Microbes: "The Good, the Bad and the Ugly"

Have you ever paused to think about what is actively living in and on your skin: microbes? The human integumentary system does not merely consist of living epithelial cells that mature, desquamate, and shed as dead skin flakes within a few weeks. These cells form an indispensable part of our primary innate defense mechanism—acting as a physical border and a dynamic frontline between our internal physiology and the outside world.

However, we are far from alone. Our skin is also home to a vast, complex ecosystem of non-human resident microbes and transient visitors. This microbial world includes bacteria, fungi, yeasts, viruses, and even microscopic parasites such as the Demodex mite. The latter in particular tends to make people itch spontaneously just thinking about it! Yet, understanding this ecosystem is vital for maintaining dermatological health.

Disclaimer: The clinical information presented in this article is intended solely for educational and professional informational purposes. Changes to skincare regimens, therapeutic interventions, or diagnostic protocols should always be evaluated in consultation with a qualified healthcare professional.

Dust mite and demodex mites on your skin - drawing by Marcelline Goyen BSc

Commensal Resident Microbes: The Safe Protectors

The vast majority of our skin microorganisms are commensal, resident members of the human microbiome—frequently referred to as the "good guys." Under normal, healthy physiological conditions, these microbes reside harmoniously in specific niches like the stratum corneum and deep within the hair follicles. Prominent strains, such as Staphylococcus epidermidis, actively protect our skin by secreting antimicrobial peptides and maintaining an acidic skin surface pH, which naturally deters harmful invaders.

However, balance is everything. Under altered environmental or systemic conditions—such as a disrupted skin barrier, chemical exposure, or a shift in the cutaneous microenvironment—these reliable residents can pivot. When the ecosystem shifts into a state of microbial dysbiosis, certain commensal strains can become opportunistic pathogens. For instance, Cutibacterium acnes is a normal resident, but when sebaceous environment parameters change, it can proliferate rapidly and contribute to inflammatory acne vulgaris.

Transient and Pathogenic Microbes: The Uninvited Guests

In contrast to our permanent residents, transient microbes are passing guests picked up from our daily environment. While many of these visitors are entirely harmless and disappear with proper hygiene, genuine pathogens can also attempt to colonize the skin. These "bad guys" pose a significant risk to the integrity of the skin shield and, in severe cases, to systemic health.

When a pathogen like Staphylococcus aureus exploits a compromised skin barrier, it does not just cause localized irritation. It can trigger deep-seated inflammation, amplify chronic conditions like atopic dermatitis, or induce severe infections. Because a localized breakdown in microbial diversity can rapidly cascade into systemic health challenges, understanding the precise composition of the skin microbiome is a clinical necessity. In dermatological health, targeted prevention and barrier maintenance are always superior to reactive crisis management.

Clinical Pillars for Nurturing the Skin Microbiome

How do we support and protect the microflora that keep the epidermal barrier intact? To effectively answer this question in clinical practice, advanced skin professionals must evaluate several key parameters that govern microbial survival and behavior.

Microbiome Variable	Clinical Focus & Diagnostic Relevance
Microbial Identity	Pinpointing exactly which specific resident, opportunistic, and transient strains are present on the tissue.
Inter-Species Dynamics	Understanding how distinct bacterial, fungal, and viral populations interact and balance one another.
Environmental Parameters	Assessing the exact cutaneous conditions—such as sebum production, moisture retention, and skin surface pH—required for beneficial flora to thrive.
Nutritional Sources	Evaluating the specific metabolic inputs, from localized sebum and sweat components to systemic cellular nutrition, that feed the microbiome.
Anthropogenic Influence	Analyzing how human choices—ranging from topical cosmetic formulations and aggressive hygiene habits to stress rhythms—alter the microbial landscape.

If you are a dermal professional or skin enthusiast eager to explore these questions through a rigorous, science-backed framework, you can find deep-dive analyses, clinical protocols, and real-world case studies in my textbook, The Skin-Gut Axis, available globally via skin-gut-axis.com.

References & Further Reading

1. Munteanu, C.; Turti, S.; Marza, S.M. Unraveling the Gut–Skin Axis: The Role of Microbiota in Skin Health and Disease. Cosmetics 2025, 12, 167. https://doi.org/10.3390/cosmetics12040167 LINK

2. Byrd, A., Belkaid, Y. & Segre, J. The human skin microbiome. Nat Rev Microbiol 16, 143–155 (2018). https://doi.org/10.1038/nrmicro.2017.157 LINK

3. Goyen Marcelline. 'De huid-darm connectie' book (2019) - ISBN 9789463456210 Volume I

4. Goyen Marcelline. 'De wonderlijke samenwerking tussen huid & darm' book (2023) - ISBN 9789464812329 Volume II (Dutch)

5. Goyen Marcelline. The amazing world of the skin-gut axis, including the role of the microbiome' (2024) - ISBN 978946511346 Volume II (English)

6. Goyen Marcelline. 'Die wunderbare Zusammenarbeit zwischen Haut&Darm' (2025) - ISBN 9789465117164 Volume II (German)

⚖️ Medical Disclaimer: The information provided on this website, including articles, textbook references, and educational materials, is for informational and educational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or another qualified healthcare provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.

Thank you for reading my blog post.

Marcelline Goyen, BSc | Dermal Therapist | Skin-Gut Axis Specialist | Author Founder of www.skin-gut-axis.com

About Marcelline Goyen, BSc Marcelline Goyen, BSc, is a dermal therapist (formerly practicing), international educator, and author specializing in the complex interactions of the skin-gut axis. With over two decades of clinical experience, she is known for her pioneering work on the skin-gut-brain connection and integrative approaches to skin health. To make her knowledge more widely accessible, her work has culminated in the publication of two books, which are used as reference works in the field of holistic skin rehabilitation. Alongside her writing, she shares her insights globally through masterclasses and webinars.

Discover more about her books and clinical vision at www.skin-gut-axis.com, or connect with Marcelline on LinkedIn.

More about Marcelline