Did you know that the skin is the largest organ in our body, reaching a surface area around 2m2? And that it is made up of different layers that act as a protective barrier? Surely yes. However, you may not know that the skin is much more than the cells that form it: it is a complex ecosystem in which a large number of microorganisms coexist.
This intricate system must work perfectly so that our skin can perform its function correctly and problems from an imbalance of our “skin ecosystem” or microbiome do not arise.
If you continue reading this article, you will discover:
- What is known as microbiota and microbiome.
- What role does the microbiota have in our skin and what happens when there is an imbalance.
Microbiota and microbiome.
The term microbiota refers to the entire set of microorganisms present in our body. However, the concept of the microbiome goes further: it encompasses, in addition to the microorganisms themselves, all their genetic material and all the environmental factors that surround them. Thus, we could say that the microbiome would be a large ecosystem that must be kept in balance.
Regarding its composition, the highest percentage is represented by bacteria, followed by fungi, viruses and, finally, arthropods. It is estimated that there could be such a number of microorganisms in our body that would represent approximately 1.5kg of our own weight.
They are found on the surface or within many tissues and fluids of the human body including the skin, mammary glands, placenta, semen, uterus, ovarian follicles, lungs, saliva, oral mucosa, tract gastrointestinal… Wherever you imagine, they are.
Microbiota and the skin barrier.
As we described previously, the skin is not only a physical barrier, but also an immunological one, which protects us from possible external threats. For the proper functioning of this skin barrier, the microbiota plays a fundamental role. These microorganisms live in symbiosis with their host, that is, there is a perfectly balanced relationship in which the microbiota acts by preserving the barrier function of the skin and, at the same time, finds a habitat in us.
It is important to emphasize that the microbiome of the skin, as it happens with that of other areas of our body, is a dynamic and changing structure. The microorganisms that make it up begin to form part of our skin from the very moment of our birth: those born by natural childbirth have a microbiota similar to the vaginal microbiota of the mother; while those born by cesarean section have a microbiota more influenced by the external environment. This microbiome evolves over the years until it stabilizes and is unique for each person, as if it were their own fingerprint.
Throughout our skin, the composition of the microbiota varies depending on the microenvironment in which we find ourselves (oily, hydrated areas and drier areas). Age, sex, environmental factors, lifestyle, use of cosmetics and antibiotics also affect its composition. Despite all these variations, under normal physiological conditions, the “ecosystem” remains in balance; and problems occur when this balanced state is broken.
Microbiota and atopic dermatitis.
The pathogenesis of atopic dermatitis is known to include a defect in the epidermal barrier, immunological dysregulation, an itch-scratch cycle, or an imbalance in the skin microbiota.
As we mentioned in a previous article, there are environmental and epigenetic changes that can affect the immune system and the functionality of the epidermal barrier; but the microbiota constitutes an additional physiological barrier against external pathogens by not letting them grow on our skin: microorganisms form a “protective shield” around the entire body.
Despite the fact that we already know that the skin is a dynamic habitat and highly exposed to external factors, the microbiome is capable of self-regulation and maintains a certain stability in terms of its composition. When this balance is broken, either by external or internal factors, the type of microorganisms that live in that area of the skin can also change. It has been seen that in skin with atopic dermatitis lesions, there is an increase in bacteria of the Staphylococcus aureus species compared to healthy skin. That is, this “protective shield” is broken and microorganisms appear (or increase in number) that should not, giving rise to a pathology.
Taking care of our skin and microorganisms that live in it can help prevent the appearance of these types of skin conditions from occurring or can be treated more easily.
Don’t forget that the skin and its microbiota are our shield. Take care of it!
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Keywords: microbiota, microbiome, skin barrier, atopic dermatitis
References:
Structure, Function and Diversity of the Healthy Human Microbiome. The Human Microbiome Project Consortium. Nature, 2012; 486(7402): 207–214.
Blicharz L, Rudnicka L, Czuwara J Waśkiel-Burnat A, Goldust M, Olszewska M, Samochocki Z. The Influence of Microbiome Dysbiosis and Bacterial Biofilms on Epidermal Barrier Function in Atopic Dermatitis—An Update. Int. J. Mol. Sci. 2021, 22, 8403.
Ferček I, Lugović-Mihić L, Tambić-Andrašević A, Ćesić D, Grginić AG, Bešlić I, Mravak-Stipetić M, Mihatov-Štefanović I, Buntić AM, Čivljak R. Features of the Skin Microbiota in Common Inflammatory Skin Diseases. Life (Basel). 2021 Sep 14;11(9):962.
Byrd AL, Belkaid Y, Segre JA. The human skin microbiome. Nat Rev Microbiol. 2018 Mar;16(3):143-155.
