The moment we are born, each of us is implanted with trillions of bacteria cells that live and thrive on our skin. These cells make up what is known as the skin microbiome. The exact makeup of each person’s microbiome is as unique as a fingerprint and over time with meeting new people, interacting with environments, adopting different lifestyles, and changing with age, so is the diversity and health of this microbiome.
Something as simple as leaving the house can cause our skin’s microbiome to adapt. It is also possible to live with a person, to the point where the microbiomes of two people become so intertwined that algorithms can correctly identify cohabiting pairs based on their microbiomes alone.
“The skin microbiome is a natural ecosystem of bacteria that live on the skin,” explains plastic surgeon and dermatologist Dr. Martin Kinsella. “It works to protect the skin from harmful pathogens to the point that a well-functioning skin microbiome is the foundation of a healthy immune system.”
When microorganisms colonize our skin, they thrive by feeding on the salt, water, and oil (sebum) that we naturally produce. This keeps our ecosystem in delicate balance. When a pathogen comes into contact with a thriving microbiome, it is prevented from colonizing the skin through crowding. 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 infections, our microbiome is its shield.
Indicative of this protective nature, studies have found links between babies born by caesarean section, which means they don’t come into contact with vaginal microbes during delivery, and increased incidences of allergies and asthma later in life. UNICEF has made skin-to-skin contact a key component of birth standards, citing the power of this practice to “enable the colonization of the baby’s skin with mother-friendly bacteria, thus providing protection from infection”.
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When this protection is weakened by spoilage, or by the presence of harmful bacteria, the delicate balance of the microbiome can be thrown off. 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 per cent of the UK population suffers from a microbiome-related skin complaint each year.
“The chemicals in skin care products can disrupt the skin’s natural microbiome of the delicate balance between oil and bacteria,” says Kinsella. “Antibacterial agents are a big factor in this, and other products that contain harsh chemicals alter the skin’s natural pH balance.”
This was seen during COVID-19 when a study found that “changes in microbial flora” resulting from increased use of disinfectants are associated with increased skin damage. Medications and antibiotics have been shown to kill the beneficial bacteria on the skin, making it more susceptible to infection. Conditions like acne and dandruff can also be a sign of an imbalanced skin microbiome.
Once the balance is imbalanced, the microbiome cannot effectively protect against more bad bacteria, and a vicious cycle occurs. With eczema, bad bacteria cause the skin to become inflamed, which causes the skin to scratch and thus damage it further, causing more harmful bacteria to enter.
Kate Porter, founder of skincare brand Harborist, explains more: “Severe eczema and dry skin have been linked to an abundance of bacteria known as Staphylococcus aureus. There is evidence that the limit aureus bacteria, to restore a variety of microbiome, reduces eczema symptoms. But it’s a chicken-and-egg case. Does an unbalanced microbiome cause these problems or vice versa? “
As we age, our microbiome goes through other transformations. This transformation is not only related to visible changes – wrinkles, dark spots, dry skin – but to internal changes as well. There is one school of thought that as our microbiome changes with age, our skin’s ability to protect us from UV rays decreases. This increases our susceptibility to skin cancer.
Recent studies have shown that the skin microbiome is a more accurate predictor of chronological age than the gut. Using this theory, a person’s microbiome could be used, at least hypothetically, to assess life expectancy. “Aging has a profound effect on the skin’s microflora in terms of both types and numbers,” explains the team leading SMiHA. “Therefore, human skin provides an excellent system for determining how changes in the microbiome affect biological lifespan.”
This is not to say that microbes are the only cause of such conditions and diseases – genes and lifestyle play important roles, for example – but disruption of our skin’s ecosystem is a contributing factor. Modern hygiene habits, including daily bathing, are thought to play a role. Harsh skin care products are often to blame. Researchers from Finland have found a relationship between the increased prevalence of allergies and atopic conditions and the decline in biodiversity in urban areas.
However, just as everyday products have been linked to disrupting the microbiome, an increasing number of brands are now releasing products saturated with prebiotics, probiotics, and post-biotics to counterbalance this disruption.
While probiotics refer to “friendly” bacteria, and prebiotics are the nutrients that feed these probiotics, prebiotics are what’s left in the process. The jury is still out on debating the benefits of topical probiotics and primary skincare, largely due to the beginning of the research and the fact that the use of live bacteria in cosmetics is a sticking point in regulation, but post-biotics in skin products are already common.
Lactic acid, for example, found in ready-made skincare preparations, is a by-product of the fermentation of a probiotic called Lactobacillus. When used topically, it has been shown to hydrate, reduce signs of aging, and calm redness.
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Researchers are also looking into the possibility of microscopic implants to solve skin problems. In a study published in 2018 in the journal JCI InsightAbundance aureus bacteria The microbiome of people with atopic dermatitis has been replaced by bacteria known as rosomonas mucosa “With significant reductions in measures of disease severity and topical steroid requirements”.
However, the problem with nearly all of these findings is that the underlying mechanisms of the skin microbiome remain largely unknown, and their impact is disputed. For all the studies linking cesarean deliveries to lowered immunity, there are studies that either fail to find the same associations, or find statistically irrelevant associations.
“When skin is healthy, we think the skin microbiome is healthy too, but we don’t know this for sure,” the SMiHA team says. “Our understanding of how to manipulate the skin microbiome with everyday products is still very poor.”
“As consumers, we like to be able to associate a specific ingredient in skincare with a specific outcome, but several factors influence our microbiome,” Porter adds. “It’s hard to change it for the better using just one thing because the microbiome varies so much between people. There is also no one better direction to change it.”
Recently, initiatives such as the Skin Trust Club have begun collecting samples from the public to delve into the health of our skin and its inner workings. From a biomedical standpoint, researchers are also exploring the effects of antibiotics on the skin microbiome, to see if we can reduce antimicrobial resistance.
This is much easier said than done.
The SMiHA team concludes, “There is huge commercial traction to explore how to improve skin through an approach that targets the microbiome.” “However, separating the effects of topical products on the microbial population and skin cells – in a way that allows us to be able to definitively say that targeting microbes leads to healthier skin – is a difficult challenge for the scientific community.”
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