You’ve probably heard about the gut microbiome. But the gut isn’t the only place microorganisms hang out on your body. The skin, our largest organ, is teeming with microbial activity we can’t see. It’s home to a diverse ecosystem of bacteria, mites, viruses, and fungi. That ecosystem—the microorganisms, their genes, and even the surrounding environment 1 —that’s your skin microbiome.
The Connection Between the Skin and the Gut Microbiomes
Our skin and our gut are both critical to keeping our bodies in good working order, and they both mediate the body’s relationship with the outside world. 2 The skin protects us from pathogens and regulates our temperature; the gut is our vehicle for digesting food and gaining nutrients that fuel us. They are both home to a dense nexus of nerves, and they both host microbiomes.
The connection between the gut and skin microbiome is called the gut-skin axis. Scientists are still discovering the extent of the relationship between the gut and the skin, but studies in mice and in people show that introducing changes to bacteria in the gut can influence the skin and the immune system. 3 The skin microbiome also has an important role to play in maintaining immune function and mediating inflammation.
Understanding the Skin Microbiome
Most people have around 1000 species of bacteria living in their skin microbiome.4 But your microbiome isn’t uniform across your entire body. It has three major habitats: sebaceous, moist, and dry, and the bacteria vary accordingly–what’s growing behind your neck can be different from what’s in your armpits, on your back, or between your toes. The most diverse bacterial environment on your skin: your forearm.5
The microbiome forms early–likely even before birth, as bacteria from the mother travels through the blood to the developing baby. 6, 7 The way that children are born also influences their skin microbiome: when a baby passes through the vaginal canal, there’s a microbial transfer that seeds bacteria on the newborn’s skin. 8 Babies born via c-section are less likely to receive the same diversity of bacteria, and are at higher risk of developing eczema and other immune-driven diseases. 9
Studies show that the bacteria in the skin microbiomes of healthy adults remain relatively stable over time, even as our environments change.10 But when the skin barrier is compromised, it creates an opportunity for opportunistic bacteria to overgrow and disrupt the balance of the microbiome. That imbalanced state is called dysbiosis, and it can result in an altered immune response.11 The result: inflammation, which can make existing skin conditions worse.
The Microbiome’s Role in Inflammatory Skin Conditions
Bacterial overgrowth can exacerbate eczema, acne, rosacea, and other skin conditions. The common culprit: staph aureus, a bacteria that’s the primary cause for skin infection worldwide.
When people with eczema get itchy and scratch their skin, they damage the skin barrier, giving staph aureus the opportunity to colonize and crowd out good bacteria. 12 The worse your eczema is, the more staph aureus your skin likely harbors.13 Staph aureus also plays a role in inflammatory acne. When it interacts with acne-causing bacteria, it secretes toxins that bind to keratin-producing cells and further inflame the skin. 14 Staph aureus operates similarly in rosacea by stimulating receptors that drive inflammation. 15, 16 People with psoriasis have increased levels of staph aureus on their skin and in their nasal passages. 17 Staph aureus overgrowth can also slow down wound healing and increase inflammation associated with aging.
Staph aureus infections have historically been treated with antibiotics. While antibiotics are generally effective at curbing infections, they do not target staph aureus alone, and can also wipe out beneficial bacteria that support a healthy skin and gut microbiome. Overuse of antibiotics can lead to antibiotic resistance. Many strains of staph aureus, including Methicillin-resistant staph aureus, commonly known as MRSA, are antibiotic resistant.
Restoring Microbiome Balance
There are several ways to change the balance of bacteria on your skin: you can introduce new bacteria, or you can selectively eliminate the bacteria that’s driving inflammation. Repairing the skin barrier can also help prevent further colonization.
You can introduce new bacteria to your skin microbiome with topical products containing probiotics (live cultures of beneficial bacteria). Other biotic skincare products can contain prebiotics (ingredients that fuel the growth of bacteria) or postbiotics (bioactive ingredients that are the byproduct of the bacterial fermentation process.)
Another way to change the makeup of your skin microbiome: kill off the bacteria that are causing harm. Endolysin science offers a way to target staph aureus while leaving beneficial bacteria intact. 18 Specific endolysins can invade staph aureus’s cell walls and destroy it from the inside. 19 This technology offers a new paradigm for addressing inflammatory skin conditions and is key to developing sustainable alternatives to antibiotics.
Repairing the skin barrier is critical to maintaining a balanced skin microbiome. Skin barrier repair requires hydrating, calming, and moisturizing the skin.
Microbiome Science: A New Frontier
The skin microbiome is a rich, complex system–one that researchers are still working to fully understand. That exploration has powerful implications: microbiome science has the potential to change the way society understands disease and addresses human health.
1: Pintas S, Lio P. Manipulating the Microbiome: What is Known, What is Unknown? Journal of Integrative Dermatology. Published online February 25, 2022.
2: Salem Iman, Ramser Amy, Isham Nancy, Ghannoum Mahmoud A. The Gut Microbiome as a Major Regulator of the Gut-Skin Axis. Frontiers in Microbiology, 9 (2018). https://www.frontiersin.org/article/10.3389/fmicb.2018.01459 doi: 10.3389/fmicb.2018.01459
3: O'Neill, C. A., Monteleone, G., McLaughlin, J. T., & Paus, R. (2016). The gut-skin axis in health and disease: A paradigm with therapeutic implications. BioEssays : news and reviews in molecular, cellular and developmental biology, 38(11), 1167–1176. https://doi.org/10.1002/bies.201600008
4: Your body is a Wonderland ... of Bacteria. Science. (2009, May 28). Retrieved April 8, 2022, from https://www.science.org/content/article/your-body-wonderland-bacteria
6: Dunn AB, Jordan S, Baker BJ, Carlson NS. The maternal infant microbiome. MCN: The American Journal of Maternal/Child Nursing. 2017;42(6):318-325. doi:10.1097/nmc.0000000000000 373
7: Pintas S., ibid.
8: Dunn AB, ibid.
9: Dunn AB, ibid.
10: 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
11: Park, Y.J. & Lee H.K. The Role of Skin and Orogenital Microbiota in Protective Immunity and Chronic Immune-Mediated Inflammatory Disease. Frontiers in Immunology, 8, (2018). https://www.frontiersin.org/article/10.3389/fimmu.2017.01955. doi: 10.3389/fimmu.2017.01955
12: Pintas S., ibid.
13: Pintas S., ibid.
14: Dréno, B., Dagnelie, M. A., Khammari, A., & Corvec, S. (2020). The Skin Microbiome: A New Actor in Inflammatory Acne. American Journal of Clinical Dermatology, 21 (Suppl 1), 18–24. https://doi.org/10.1007/s40257-020-00531-1
15: Totté, J. E., van der Feltz, W. T., Bode, L. G., van Belkum, A., van Zuuren, E. J., & Pasmans, S. G. (2016). A systematic review and meta-analysis on Staphylococcus aureus carriage in psoriasis, acne and rosacea. European journal of clinical microbiology & infectious diseases : official publication of the European Society of Clinical Microbiology, 35(7), 1069–1077. https://doi.org/10.1007/s10096-016-2647-3
16: Yamasaki, K., Kanada, K., Macleod, D. T., Borkowski, A. W., Morizane, S., Nakatsuji, T., Cogen, A. L., & Gallo, R. L. (2011). TLR2 expression is increased in rosacea and stimulates enhanced serine protease production by keratinocytes. The Journal of Investigative Dermatology, 131(3), 688–697. https://doi.org/10.1038/jid.2010.351
17: Totté, J. E., ibid.
18: Murray, E., Draper, L. A., Ross, R. P., & Hill, C. (2021). The Advantages and Challenges of Using Endolysins in a Clinical Setting. Viruses, 13(4), 680. https://doi.org/10.3390/v13040680