Q&a / Beauty & Science
”Massive DNA sequencing studies have expanded our insights of the ecological and functional characteristics of the microbiome”
On the latest research on how good and bad bacteria affect our skin
15 Feb 2021

Dr. Ann’Laure Demessant, pharmacist and microbiologist, is in charge of La Roche Posay’s Scientific Communication and a specialist of probiotics and the impact of bacteria on human health.

For those who don’t know, why is the microbiome so important for our wellbeing?

— We are living with millions of bacteria lying in and on our skin. These bacteria play an essential role in our skin health. Thus, commensal bacteria — those which lie naturally on our skin and work for our health — shield our skin against external aggressors: they reinforce our skin barrier, protect us against infections by bad bacteria. These good bacteria also help us to be protected against internal aggressions such as chronic inflammation, responsible for skin diseases, or skin aging. Moreover, from an early age, our skin bacteria discuss with our immune system to train it to recognize the good things from the bad things, and thus not to overreact to potential irritants or allergens for example. Indeed a balanced microbiome will decrease inflammatory reactions; when an imbalanced one will trigger or aggravate inflammatory skin diseases, such as acne or atopic eczema, says Demessant.

The brand, she explains, is convinced of the huge impact of skin microbiome in the maintenance of healthy skin.

— That’s why we’ve been pioneering skin microbiome science since 2011 and conducted 19 clinical studies which have been published in 13 scientific publications and presented in the greatest dermatological congresses, EADV and WDC. We are passionate about the impact that bacteria, good or bad, have on skin. In the last years, the knowledge about skin microbiome has made huge progress and allowed us to better understand the impact of skin microbiome on skin diseases. Indeed, a loss of microbial diversity (when microbiome loses its balance) is associated with skin discomforts: dryness aggravation, spots, itching, or pain. We’ve conducted clinical studies to better understand the evolution of microbiome in patients with chronic skin diseases such as atopic dermatitis, acne, psoriasis, or rosacea.

A great number of scientific studies have shown that on atopic eczema lesions, the microbiome is imbalanced due to a bacteria, named Staphylococcus aureus

— It proliferates excessively and inhibits the growth of commensal bacteria — the beneficial ones. Staphylococcus aureus overgrowth is directly associated with itching and pain sensations. La Roche Posay Research was able to demonstrate that when the microbiome is rebalanced, the skin comfort is regained with a decrease of dryness and itching sensations. It was also demonstrated that the bacteria Staphylococcus bacteria are able to secrete a kind of shield, named biofilm, that promotes their adhesion and persistence on skin.

— In the same way, Cutibacterium acnes bacteria is associated with acne spots. Indeed, this bacteria is keen on sebum and is then able to proliferate in oily skins. It’s mainly responsible for the inflammatory reaction triggering redness and pain at the spot level. On the surface of spots, some Staphylococcus also contribute to this inflammatory reaction, which may induce pigmentary marks persisting even a long time after the spot’s disappearance.

— For 10 years now, we’ve been studying the skin microbiome and its potential disbalances to be able to design dermo-cosmetics enabling to take care of our microbiome and rebalance it to keep skin healthy. We are also developing pre- and post-biotic ingredients such as Aqua Posae (or APF), which is a bacteria coming from a natural thermal spring water. When grown in La Roche Posay water, this bacteria is empowered and gain new capabilities allowing it to strengthen natural skin defenses, especially in rebalancing skin microbiome and reinforcing skin barrier.

Why has the last couple of years seen this increased focus on the microbiome?

— The Human Microbiome Project (HMP) began in 2008 to examine how changes in the human microbiome were associated with human health or disease. It first focused on gut microbiome which is the main one in terms of the amount of microbes. Then new body sites were explored, such as skin, a few years later. We know now that more than 500 different species of bacteria, viruses, and fungi live permanently on and in our skin. It is a complete, although invisible, ecosystem living in symbiosis with human beings. The balance between the different microbial species is different from one person to another and is as unique as fingertips. It depends on genetics, food habits and lifestyle, the job we do, pets we have at home, and more. The microbiome is also very different from one skin zone to another: some areas are dry and fresh, as the skin of our arms, while some are moisty and hot, as in our mouth, and others are rich in sebum, as on the T-zone on our face. Microbes have their specific needs, depending on their favorite temperature of growth, the nutrients they need, and more, that will determine their capabilities to colonize a specific skin area, says Demessant, adding,

— Massive DNA sequencing studies have expanded our insights and understanding of the ecological and functional characteristics of the microbiome. Researchers have even discovered that bacteria have an impact on skin gene regulation. A better knowledge of the bacteria on our skin and how bacteria interact with each other and with the skin will help to better treat some skin diseases and maintain it in good shape. 

Clinical study by La Roche Posay

Demessant’s insights on how to take care of our skin microbiome:

— First of all, do not attack it! Our microbiome has to be considered as a friend — we have to protect it. Use of harsh cleansing products may disturb our microbiome, and especially on a fragilized or sensitive skin.

— Thus, people with acneic skin often cleanse their skin more frequently. These numerous cleansings may alter skin barrier functioning, especially in the case of the use of alkaline soaps or cleansers. Indeed, the pH of the skin is naturally acidic, and maintaining this acidity is essential for the health of skin bacteria. Using syndets, which are cleansers without soap, designed to be at physiological pH (corresponding to the skin pH) will protect skin microbiome balance.

— In addition, it is also possible to act more specifically, bringing our microbiome the nutrients it needs thanks to specific dermo-cosmetic care. These nutrients are called prebiotics. It can be sugars or mineral salts that feed our microbiome and help its good functioning. Adding a prebiotic allows helping the good bacteria to grow and to rebalance a poor microbiome. For example, La Roche Posay thermal water has a unique and specific mineral composition providing beneficial prebiotic properties for the skin.

— Some ingredients act directly on bacteria’s growth, decreasing their adhesion on the skin. For example, Microresyl is a natural ingredient that prevents Staphylococcus aureus’ adhesion on the skin to limit its growth. As it’s (the Staphylococcus aureus) mainly responsible for skin itching and irritation for atopic-prone skin, it contributes to restoring skin comfort. In addition to the prebiotic power of La Roche Posay Thermal water, Lipikar AP+M balm contains Microcresyl and APF, which both rebalance microbiome, to soothe the skin and improve people’s well-being and quality of life.