What You Need to Know About the Skin’s Microbiome
The skin’s microbiome is the community of microbes — such as bacteria, fungi, and other microorganisms — that live in and on the human body. Although some of these microbes can be problematic at times, many of them are essential for immune system health, protection from pathogens, and other critical functions.
Whether you’re a professional seeking to anticipate skin health trends in 2023 and beyond or a consumer looking for tips on preserving your skin health, continue reading to learn more about this little-known yet critical part of the skin biome.
A Skin Microbiome Primer
The skin’s microbiome varies slightly from person to person. Although there’s no such thing as a “standard” microbiome, the species of microbes that reside on the skin tend to be similar, just in different proportions from person to person. The specific makeup of an individual’s microbiome arises early in life from a variety of genetic and environmental factors. For example, babies delivered via cesarean section have different microbes than those born vaginally, and variables such as gestation period and feeding method (e.g., bottle-fed versus breastfed) all contribute to the development of one’s microbiome.
However, it is important to note that what lives in and on your skin depends on the environment produced by your skin, as well as what you put on your skin. So, you won’t necessarily alter your skin microbiome composition just by touching things (e.g., doorknobs and dirt). The strains that take up residence, or “engraft,” on your skin must find that area of the body favorable. This is similar to why animals migrate; they settle down where the conditions are favorable to their existence.
The skin microbiome also changes with age. Differences in body mass index, exercise habits, lifestyle (e.g., smoker versus non-smoker), and other factors help determine individual differences in skin microbiomes. As a person ages, the body produces fewer skin cells and less sebum, and the skin barrier weakens — all of which deprives skin microbes of some of the food they need for nourishment. Consequently, older people can miss some of the more beneficial microbes of the skin microbiome.
Your skin does an excellent job of keeping you safe, but it isn’t impregnable. In fact, your skin’s interactions with outside elements, such as skin microbes, enable it to overcome threats that would otherwise damage the body. For instance, the most abundant bacteria species on the skin, Cutibacterium acnes, produces large amounts of antioxidants, one of which is called RoxP and is as strong as vitamin C, which helps to protect the skin from free radical stress caused by free radicals created by sunlight and pollution. This is a potent antioxidant that is secreted in copious amounts all day long by your skin microbes (well, the right strains, at least). This symbiotic relationship and its importance to healthy functioning is something to keep in mind when making decisions on which topical products to use and how they affect those healthy microbes.
What Consumers and Skin Care Professionals Need to Know About the Skin’s Biome
Skin is the largest human organ and the body’s first line of defense in keeping us safe from pathogens and other threats in the environment. So, though it makes sense that we usually don’t associate healthy skin with bacteria, as we have mentioned, your skin is nonetheless home to hundreds of species of bacteria, many of which contribute to your personal well-being. In fact, animals with fewer microbes than what’s typical for their species tend to have more health issues than their counterparts with more hearty microbiomes. The combination of your skin, your skin microbiome, and the environment that houses them both composes the overall skin biome.
Skin microbes within their biome keep your immune system robust by communicating with your body’s T cells and coordinating to jointly identify harmful microorganisms and rally your immune system’s defense mechanisms against them. In contrast, a lot of common skin disorders result, in part, from a disrupted skin microbiome. For example, acne, athlete’s foot, and eczema are more likely to be present in individuals with fewer healthy skin microbes in certain skin areas. Recent evidence suggests that several bacteria and fungi species might even protect you from nonmelanoma skin cancers.
So long as your skin microbiome maintains a stable population of healthy skin bacteria, these microorganisms will typically outcompete pathogens and other unwelcome microbes for resources and living space. This equilibrium is critical for combating inflammatory skin conditions and achieving healthy and beautiful skin.
Furthermore, the same environment that healthy skin bacteria thrive in can be an unsuitable habitat for pathogens — specifically, an environment with a low pH level. In healthy skin, the low pH level is held stable through a specific sequence of events. Cutibacterium acnes, (formerly known as Propionibacterium acnes) work together to metabolize sebum from the skin and transform it into propionic acid, which in turn regulates the growth of the alkali-loving Staphylococcus aureus, which can only thrive in a high pH environment. If sebum production falls — or the skin pH level is disrupted for other reasons — the Staphylococcus aureus infection rate will skyrocket. This is one of the reasons that the use of strong retinoids, which reduces skin oils and thus Cuitbacterium acnes production of propionic acid, can have a side effect of a higher prevalence of Staph infections.
So, if this is all true, then why are so many skin care products intentionally or unintentionally formulated to damage the skin microbiome? It is known that during the Civil War era, reformers campaigned for improved hygiene standards, initiating a chain reaction where cosmetic and cleaning product manufacturers emphasized cheaper ingredients with antibacterial properties, including fragrances and other additives that kill good bacteria and make the skin a less appealing habitat for healthy microbes. This persists today, despite the advances in overall societal hygiene habits, without regard to how it affects our health.
Probiotics are a hot topic in the health world, and probiotic topical products show some potential to help maintain a healthy skin biome. However, this is true only when the definition of “probiotic” is used inaccurately. Probiotics are living microorganisms that aid some aspects of human health. But it is important to note that only those microbes that are able to engraft and thrive on skin can act as probiotics. Therefore, the Lactobacillus that is found in your yogurt cannot necessarily act as a skin probiotic, even if it is a wonderful gut probiotic. It is also important that we consider the whole skin biome (human skin, microbiome, and the skin environment) when thinking about using probiotic topicals. Thus, we should strive for skin biome care, not just skin care. Skin biome care involves topical probiotic skin care treatments such as creams, cleansers, and serums that are “biome-conscious.”
Also, when it comes to daily hygiene, “cleaner” isn’t necessarily better. Although people associate microbes such as bacteria with disease, your skin’s microbiome isn’t your enemy — it’s one of your strongest allies. Also, the oils of the skin are there for a reason. We should not aim to remove oils, only to balance them. Having the right microbes on the face will help to do this in a significant way. So, the next time you’re shopping for cleansers, take a moment to consider the well-being of your microbe friends and go with a nonsoap, nonfoaming, gentle, low-pH option.
The primary thing to understand is that there are millions of microbes living on your skin at all times. These microbes are constantly secreting substances that can either be helpful or harmful for your skin, and what they secrete depends on the environment and food you provide them. Be careful which products you use because some products might harm your skin’s microbiome or cause them to become defensive (leading to inflammation). Remember that each person’s skin microbiome is slightly different, and your skin biome changes as you age. So, look for legitimate skin probiotic topicals that use skin-relevant strains of microbes, and provide the right environment and food sources for a healthy and balanced skin biome.
Thomas Hitchcock, Ph.D., is the Chief Science Officer for Crown Laboratories, where he oversees clinical development, medical affairs, biological sciences, product development, and research and development for the privately held, fully integrated global company dedicated to developing and providing a diverse portfolio of safe and effective scientific solutions for life-long healthy skin.