For New York dermatologist Doris Day, MD, co-author of the new book Rebooting the Biome which she cowrote with genetic scientist Thomas M. Hitchcock, PhD, the secret to beautiful skin lies in understanding the role the skin’s microbiome plays in keeping it balanced, clear and preventing skin aging. “Your skin microbiome can do so much for you. It can help with how your skin ages, how much redness and inflammation you have and can help against breakouts to keep your skin healthy and clear,” she explains.
What is the skin microbiome?
“The microbiome plays a crucial role in maintaining and repairing the skin barrier. Your microbiome is the microbes, germs, bugs, bacteria, and everything that lives in the environment. We have a gut biome, a skin biome, and many other organs have microbiomes as well.
These microorganisms interact with the skin cells and play a vital role in maintaining the skin barrier by regulating the skin’s pH, producing antimicrobial peptides, and promoting skin cell turnover. The skin microbiome produces lipids (like fatty acids and natural oils) that are necessary for maintaining the integrity of the skin barrier.”
Why is skin barrier repair important?
“The skin barrier is the outermost layer of the skin that protects against external stressors such as UV radiation, pollution, and bacteria. When the skin barrier is compromised, it can lead to skin dryness, irritation, and inflammation. We’re really in the infancy of understanding biome care, so I think of it as separate from skin care. At the same time, biome care is also paying special attention to those microorganisms that live and naturally inhabit the skin and what their balance should be, and which strains are best for what you’re trying to achieve.”
How does a healthy skin biome help with hydration?
“What happens is those microbes eat the sebum, or the oils in the skin, and they break them down into short chain fatty acids and propionic acid and antioxidants. Those work like vitamin C, they work like hyaluronic acid, and they work like humectants, so they help naturally hydrate your skin and they help to reduce the inflammatory processes that cause wrinkles.
The other interesting consideration is that your skin microbiome is not very diverse; there are not very many different microorganisms naturally co-existing there. There might be different strains, but the predominant microorganisms are C. acnes and a certain strain of Staph epidermidis. You see greater microbe diversity in people who have eczema, or psoriasis, or active acne. So that’s one of the myths and, one more interesting fact about your microbiome is that as you age, it becomes more diverse, not less as many scientists predicted, and is a sign of aging.”
What is one thing everyone should do to maintain a healthy microbiome?
“Stop over washing. That is as bad as not washing enough—it’s very harmful to the skin because you’re stripping away your skin’s natural oils and damaging your skin biome. You’re also washing away your skin’s innate immunity.”
What do you recommend for someone in their 20s and 30s?
“For someone in their 20s, the biggest change I suggest is lowering the use of oral antibiotics for acne. I suggest looking for topicals which help rebalance rather than attack microbes–like salicylic acid which is skin biome friendly when used in the 0.5-2% concentrations typically used in cleansers. Retinoids are also good, although I sometimes will suggest using them five days a week instead of seven days a week due to irritancy and also because they create an environment that mimics abundance which is what allows the skin to have the “luxury” of being able to work on rebuilding itself and build collagen, but it’s not necessarily good to always be in that state. I also recommend adopting a diet of lots of vegetables along with healthy fats, like in the Mediterranean diet, which includes olive oils, salmon and other fatty fish, walnuts, almonds, along with leafy greens and broccoli and other cruciferous vegetables. These changes will make the biggest difference in your skin.”
What about the 40s and 50s and up?
“Once you hit your 40s and 50s, you’re in that age of less collagen production, hormones are starting to wane a little bit and cell turnover is a little slower. The diversity of the biome starts to increase which is a negative thing, because now that’s a sign of aging. The change in diversity may lead to overgrowth of pathogenic bacteria and fungi, leading to skin rashes and infections. The increased diversity may also have an impact on overall health, which is just now starting to be studied. Now is the time to use products that are more protective of the biome.
It is important to hydrate better, add topical antioxidants and growth factors, and be extra careful about sun protection. Past damage is starting to show but can be slowed or sometimes even reversed with proper skin care and diet. It’s also a great time to see your dermatologist and consider a laser peel or laser resurfacing to help renew and restore more youthful, beautiful skin.”
What are some novel ways to improve barrier health?
“Scientists are discovering that mTORC2 acts as a master switch for skin health and renewal. When activated, it boosts lipid production and hydration, strengthening the skin’s protective barrier. This switch is even tuned by signals from the skin biome, which works hand in hand with your own cells. The new mTOR (mechanistic target of rapamycin) modulator, RLX-201, plays a significant role in mTORC2 activation, and early studies suggest it may enhance cellular renewal, barrier repair, and overall resilience, helping skin function as if it were younger. By combining advanced biology with the natural rhythms of the skin biome, RLX-201 represents a pro-longevity approach—supporting skin that is strong, supple, and radiant at every age.”
What’s next in microbiome-friendly skin care?
“More companies will evaluate the effect of their products and preservatives on the skin biome directly. My skincare line considers effect on the delicate balance between our beautiful and necessary microbes and looks to help them help the skin look radiant and age beautifully rather than trying to eradicate them. Other brands such as Biojuve which contains skin probiotics, created by my co-author and LaRoche Posay have also done excellent work to preserve and enhance the skin biome.”
