At the time of our birth, each of us is seeded with trillions of bacterial cells that live and grow on our skin. These cells form what is called our skin microbiome. The exact makeup of each person’s microbiome is as unique as a fingerprint and as we go through life meeting new people, interacting with environments, adopting different lifestyles and changing with the age, diversity and health of this microbiome also changes.
Something as simple as leaving the house can cause our skin microbiome to adapt. Much like living with someone, in that the microbiomes of two people become so intertwined that algorithms can correctly identify cohabiting couples based solely on their microbiomes.
“The skin microbiome is a natural ecosystem of bacteria that live on the skin,” explains Dr. Martin Kinsella, doctor of aesthetics and skin specialist. “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 thrives on feeding on the salt, water and oil (sebum) we naturally produce. This keeps our ecosystem in a delicate balance. When a pathogen comes in contact with a thriving microbiome, it is prevented from colonizing the skin by being squeezed out. 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, our microbiome is its armor.
Indicative of this protective nature, studies have found links between babies born by caesarean section, which means they do not come into contact with vaginal microbes during birth, and an increase in cases of allergies and asthma later in life. UNICEF has made skin-to-skin contact a key part of its childbirth standards, citing the practice’s power to “allow colonization of the baby’s skin by the mother’s good bacteria, thus providing protection against ‘infection”.
Learn more about the microbiome:
When this protection is weakened by damage or by the presence of harmful bacteria, the delicate balance of the microbiome can be disrupted. 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 suffers from a condition each year. skin associated with the microbiome.
“Chemicals in skincare products can disrupt the natural microbiome of skin’s delicate balance of oil and bacteria,” Kinsella says. “Antibacterial agents are a big factor in this, along with other products that contain harsh chemicals that alter 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 was linked to increased skin damage. Medications and antibiotics have been shown to destroy beneficial bacteria in the skin, making it more prone to infection. Conditions such as acne and dandruff can also be signs of an imbalanced skin microbiome.
Once out of balance, the microbiome can no longer protect against other bad bacteria as effectively, and a vicious cycle occurs. With eczema, the bad bacteria cause the skin to become inflamed, patients scratch their skin and damage it further, which lets in more bad bacteria.
Kate Porter, founder of skincare brand Harborist, further explains: “More severe eczema and dry skin have been linked to 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 imbalanced microbiome cause these problems or vice versa? »
As we age, our microbiome undergoes further changes. This change is not only associated with visible changes – wrinkles, dark spots, dry skin – but also with internal changes. According to one school of thought, as our microbiome changes with age, our skin’s ability to protect us from UV rays 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. With this theory, a person’s microbiome could, at least hypothetically, be used to gauge life expectancy. “Aging has a profound effect on skin microflora in terms of species and numbers,” explains the team leading the SMiHA. “Therefore, human skin presents an excellent system for establishing how changes in the microbiome influence biological age.”
That’s not to say that microbiomes are the sole cause of these conditions and diseases – genetics and lifestyle play an important role, for example – but disruption to our skin’s ecosystem is a contributing factor. Modern hygiene habits, including daily showers, are thought to play a role. Harsh skincare products are often blamed. Finnish researchers have found a correlation between an increasing prevalence of allergies and atopic conditions and declining biodiversity in urban areas.
Yet, just as everyday products have been associated with disruption of the microbiome, a growing number of brands are now launching products infused with prebiotics, probiotics and postbiotics to balance this disruption.
While probiotics refer to “friendly” bacteria and prebiotics are nutrients that feed those probiotics, postbiotics are what’s left in the process. The jury is still out on the benefits of topical probiotic and prebiotic skincare, largely due to the research infancy and the fact that using live bacteria in cosmetics is a hot topic. regulatory stumbling block, but postbiotics in skin products are already commonplace.
Lactic acid, for example, found in commercial skincare products, is a byproduct of the fermentation of a probiotic called Lactobacillus. When applied topically, it has been shown to hydrate, reduce signs of aging and calm redness.
Learn more about reality check:
Researchers are also studying the possibility of microbiota transplants to solve skin problems. In a study published in 2018 in the journal JCI Overviewan abundance of S. aureus in the microbiome of people with atopic dermatitis has been replaced by a bacterium known as Roseomonas mucosa “with significant decreases in measures of disease severity and topical steroid requirements”.
The problem with nearly all of these findings, however, is that the mechanisms underlying the skin microbiome remain largely unknown and its impact disputed. For all the studies linking cesarean births to lower immunity, there are studies that either fail to find the same correlations or find statistically irrelevant associations.
“When the skin is healthy, we think the skin microbiome is also healthy, but we don’t know for sure,” the SMiHA team explains. “Our understanding of how to manipulate the skin microbiome using everyday products is still very low.”
“As consumers, we like to be able to associate a specific ingredient in our skincare with a specific result, but many 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 from person to person. There’s also no best direction to change it.
Recently, initiatives such as the Skin Trust Club have begun collecting samples from the public to dig deeper into our skin’s health and inner workings. From a biomedical perspective, researchers are also exploring the effects of antibiotics on the skin microbiome, to see if we can reduce antimicrobial resistance.
It’s much easier said than done, however.
“There is huge commercial demand to explore how to improve skin through a microbiome-targeted approach,” concludes the SMiHA team. “However, separating the effects of topical products on microbial population and skin cells – in a way that allows us to say categorically that microbial targeting leads to healthier skin – is a difficult challenge for the scientific community. “
Learn more about the skin: