By the time we are born, each of us is seeded with trillions of bacterial cells that live and thrive on our skin. These cells make up what is known as our skin’s microbiome. The exact composition of each person’s microbiome is as unique as a fingerprint, and as we move through life meeting new people, interacting with environments, adopting different lifestyles, and changing with age, so does diversity and diversity. health of this microbiome.
Something as simple as leaving the house can cause our skin’s microbiome to adapt. Much like living with someone, to the extent that two people’s microbiomes become so intertwined that algorithms can correctly identify cohabitating couples based on their microbiomes alone.
“The skin microbiome is a natural ecosystem of bacteria that live on the skin,” explains aesthetic physician and skin specialist Dr. Martin Kinsella. “It works to protect the skin against harmful pathogens to the point where a well-functioning skin microbiome is the foundation of a healthy immune system.”
As the microbiota colonizes our skin, it flourishes by feeding on the salt, water, and oil (sebum) that we naturally produce. This keeps our ecosystem in a delicate balance. When a pathogen comes into contact with a thriving microbiome, it is prevented from colonizing the skin by being expelled. Our microbiome produces antimicrobial compounds and nutrients that act as a form of protection.
If our skin is the first line of defense against pathogens and injury, then our microbiome is its armor.
Indicative of this protective nature, studies have found links between babies delivered by C-section, meaning they don’t come into contact with vaginal microbes during delivery, and increased cases of allergies and asthma later in life. Unicef has made skin-to-skin contact a key component of its childbirth standards, citing the power of the practice to “allow colonization of the baby’s skin with friendly bacteria from the mother, thus providing protection against infection”.
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When this protection is weakened by damage or the presence of harmful bacteria, the delicate balance of the microbiome can become unbalanced. This imbalance has been linked to dry skin, eczema, acne and psoriasis, and according to the Skin Microbiome in Healthy Aging (SMiHA) network, around 50% of the UK population suffer from skin discomfort each year associated with the microbiome.
“Chemicals in skin care products can disrupt the natural microbiome of the skin’s delicate balance of oil and bacteria,” says Kinsella. “Antibacterial agents are a major factor in this and other products with harsh chemicals that disrupt the skin’s natural pH balance.”
This was seen during COVID-19 when a study found that “changes in microbial flora” caused by increased use of disinfectants were linked to an increase in skin damage. Medications and antibiotics have been shown to destroy the beneficial bacteria on the skin, leaving it more prone to infection. Conditions like acne and dandruff can also be a sign of an unbalanced skin microbiome.
Once out of balance, the microbiome cannot protect as effectively against more harmful bacteria, and a vicious cycle ensues. With eczema, the bad bacteria cause the skin to become inflamed, patients scratch their skin and thus further damage it, allowing more bad bacteria to enter.
Kate Porter, founder of skincare brand Harborist, further explains: “More severe eczema and dry skin have been associated with an abundance of a bacteria known as staphylococcus aureus. There is evidence that the reduction S. aureus, to restore a more diverse microbiome population, reduces eczema symptoms. But it’s a chicken and egg situation. Does the unbalanced microbiome cause these problems or vice versa?
As we age, our microbiome goes through additional changes. This change is not only associated with visible changes (wrinkles, dark spots, dry skin), but also internal changes. There is a school of thought that says that as our microbiome changes with age, our skin’s ability to protect us from UV radiation decreases. Thus increasing our susceptibility to skin cancer.
Recent studies have even shown that the skin microbiome is a more accurate predictor of chronological age compared to the gut. Under this theory, a person’s microbiome could, at least hypothetically, be used to assess life expectancy. “Aging has a profound effect on the skin’s microflora in terms of species and numbers,” explains the team leading the SMiHA. “Human skin therefore presents an excellent system for establishing how changes in the microbiome influence biological age.”
That’s not to say that the microbiomes are the only cause of such conditions and diseases (genetics and lifestyle play a role, for example), but the disruption of our skin’s ecosystem is a contributing factor. Modern hygiene habits, including daily showers, are thought to play a role. Harsh skin care products are often blamed. Researchers from Finland found a correlation between an increasing prevalence of allergies and atopic conditions and declining biodiversity in urban areas.
However, just as everyday products have been linked to microbiome disruption, an increasing number of brands are launching products infused with prebiotics, probiotics, and postbiotics to balance this disruption.
While probiotics refer to “friendly” bacteria, and prebiotics are nutrients that feed these probiotics, postbiotics are what’s left in the process. The jury is still out on the benefits of topical probiotic and prebiotic skin care, largely due to the infancy of the research and the fact that the use of live bacteria in cosmetics is a regulatory sticking point, but postbiotics in skin products are already common.
Lactic acid, for example, found in standard skincare, is a fermentation byproduct of a probiotic called lactobacillus. When applied topically, it has been shown to moisturize, reduce signs of aging, and calm redness.
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Researchers are also looking into the possibility of microbiota transplants to solve skin problems. In a study published in 2018 in the journal JCI perspectivean abundance of S. aureus in the microbiomes of people with atopic dermatitis was replaced by a bacteria known as roseomonas mucosa “with significant decreases in measures of disease severity and requirement for topical steroids.”
However, the problem with almost all of these findings is that the underlying mechanisms of the skin microbiome remain largely unknown and their impact disputed. For all the studies linking cesarean births to lower immunity, there are studies that fail to find the same correlations or find associations that are statistically irrelevant.
“When skin is healthy, we think the skin microbiome is too, but we don’t know for sure,” say the SMiHA team. “Our understanding of how to manipulate the skin microbiome using everyday products is still very poor.”
“As consumers, we like to be able to link a specific ingredient in our skin care to a specific result, but there are multiple factors that influence our microbiome,” adds Porter. “It’s hard to change it for the better by using just one thing because the microbiome varies so much between people. There is also no single best direction to change it.”
Recently, initiatives such as the Skin Trust Club have begun collecting samples from the public to gain insight into the health of our skin and its inner workings. From a biomedical point of view, researchers are also exploring the effects of antibiotics on the skin microbiome, to see if we can reduce antimicrobial resistance.
However, this is much easier said than done.
“There is a strong commercial appeal to exploring how to improve skin through a microbiome-targeted approach,” the SMiHA team concludes. “However, separating the effects of topical products on the microbial population and skin cells, in a way that allows us to be able to say categorically that microbial targeting drives healthier skin, is a difficult challenge for the scientific community.” .
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