Jessica DeFino
May 29, 2020 7:17 am
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Jessica DeFino

Oh, to be an avocado. To be born with a built-in barrier that guards my most sensitive and squishy bits. To know that nature has provided all the protection I need; to be blessed with a layer of…wait. My bad. Humans totally have that, too. It’s called the stratum corneum, also known as the skin barrier: a 0.001-millimeter-thick layer of “dead” cells, Natural Moisturizing Factors, sweat, sebum, fatty acids, ceramides, bacteria, microbes, mites, and more that serves to keep the skin safe, strong, healthy, and hydrated.

In case you didn’t quite catch that, yes, you have a magical, microscopic layer of skin that just *does* all of the things you typically rely on products to do! At least, you should have that layer of skin. Seeing as it sits right on the surface and is almost incomprehensibly thin, the barrier tends to take a beating—from products, from pollutants, from UV rays—and once it’s compromised, all sorts of problems present themselves.

I would know. I destroyed my barrier with years of aggressive treatments for acne and dermatitis which, of course, only made said acne and dermatitis worse over time. After even more years of building it back up with skin-supportive practices, I consider myself something of a stratum corneum crusader. My battle cry? Save the skin barriers!

I’m not alone in my mission. Experts agree that preserving your skin barrier is the single most important thing you can do for your skin.

“The skin barrier helps to protect the skin from toxins, bacteria, and contaminants from the external environment. It acts as a shield for our skin,” says Devika Icecreamwala, M.D., a board-certified dermatologist with Icecreamwala Dermatology. “If the skin barrier is damaged, moisture can easily escape, leaving the skin more prone to inflammation and irritation. If the skin barrier is damaged, the skin will also be more prone to infections.”

Put simply, “the skin barrier functions to keep bad stuff out and good stuff in,” says board-certified dermatologist Aanand Geria, M.D.

“This structure is comprised of about 20 layers of dead skin cells that are configured in a ‘brick and mortar’ pattern, where the dead cells are the ‘bricks’ and lipids—such as ceramides, cholesterol, and free fatty acids—are the ‘mortar,’” he adds. And while 20 layers of dead skin cells might sound like a whole lotta nothin’, it’s important to realize that these cells—formally known as corneocytes—aren’t truly dead. They still serve a biological function: hoarding moisture in the form of the skin’s Natural Moisturizing Factors (NMFs). This moisture is locked in by the lipid barrier (the “mortar” that Dr. Geria describes).

“On your lipid barrier is the acid mantle, which acts as a protective film against bacteria and viruses,” Angela Caglia, a celebrity aesthetician and founder of Angela Caglia Skincare, tells HelloGiggles. “It has a slightly acidic pH, which naturally helps to save your skin from infections or even disease. It’s made up of sebum mixed with sweat.” Changes in the pH of the acid mantle—which ideally ranges from 4.5 to 6.2 on a scale from 1 to 14, with 1 being the most acidic—can mess with its ability to neutralize invading pathogens (like acne-causing bacteria).

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The skin barrier is also home to the microbiome, or “the millions of bacteria, fungi, and viruses that live on the skin’s surface,” per Dr. Geria. “This is a mutually beneficial partnership [between the skin and microbiome] that, when disrupted, has been linked to several skin conditions.”

“Some have called the microbiome our ‘forgotten organ’ because of its role in a functioning immune system and other bodily systems,” says Paul Schulick, an herbalist and the cofounder of skincare brand For The Biome. “Our microbial friends evolved right along with us and act as our co-pilot in sensing the environment and adapting effectively. In many ways, the microbiome is just as much a part of us as our human cells.” When the microbiome is stripped or compromised, it can lead to decreased barrier function and increased instances of dermatitis, eczema, breakouts, and more. “When the skin’s microbiome is rich and biodiverse, the skin can better adapt to environmental stress and retain hydration,” Schulick says.

In addition, the stratum corneum helps protect the inner, more vulnerable skin cells from environmental aggressors—like pollution and sunlight—via the “antioxidant barrier” and “photoprotection barrier.” Pollution and sunlight can cause the breakdown of collagen and the formation of fine lines and wrinkles—so, yup, you better believe the skin barrier has youth-preserving power, too.

All of these microscopic moving pieces of the stratum corneum are dynamic and interdependent (meaning the microbiome can only thrive if the acid mantle thrives and so on). “They work collectively to maintain healthy skin, characterized by invisible desquamation [self-exfoliation], smooth texture, and elasticity,” as one research paper from the Indian Journal of Medical Research puts it.

“The importance of skin barrier cannot be overemphasized,” it continues. “The skin barrier is important to human life.”

I know what you’re thinking right now: Um, it doesn’t feel like I have a layer of skin that locks in hydration; prevents dry skin, acne, and eczema; protects from pathogens, pollutants, and UV rays; keeps me young; and exfoliates itself…And that’s probably because you, like me, have unknowingly decimated this delicate and precious layer of skin cells. Don’t feel bad. It’s (unfortunately) very easy to do.

Perhaps ironically, the number one threat to the skin barrier is… skincare.

“The skin barrier can get disrupted in numerous ways, but usually it is self-induced,” Dr. Geria confirms. He says the most common offender is over-cleansing or “mis-cleansing,” a term he coined to describe “using the wrong cleanser for your skin type.” Another is over-exfoliation—because, again, your not-so-dead skin cells serve a purpose, and getting rid of them before they’re good and ready makes the skin more vulnerable to infection, irritation, and inflammation. Not to mention dehydration. Without dead skin cells, your NMFs have no home, and your lipid barrier has nothing to hold.

“Our societal obsession with cleanliness and manipulating the skin’s appearance has led to skincare routines that tend to stress the skin’s microbiome,” agrees Schulick. “The harsh exfoliants and chemical preservatives found in most cosmetics are like white noise for your skin and its microbiome, blocking communication and altering the pH of the skin.” Dr. Icecreamwala says to be especially wary of ingredients like alcohols and fragrance for this reason.

“Ultraviolet radiation is [another] way for the skin barrier to get disrupted,” she says. “As the skin barrier continues to break down due to UV rays, you will notice photoaging that consists of wrinkles, discoloration, and change in skin tone and texture.”

It’s not just external factors that bother the skin barrier, though. “One of the leading reasons for microbiome disruption begins from within: emotional stress,” Schulick says. Studies show that stress does weaken the skin barrier, leading to moisture loss, and affects hormone production as well. “Under these conditions, your body might produce more stress hormones, like cortisol, and influence an uptick in the skin’s sebum production. This creates a more acidic environment, which alters microbiome composition and can leave skin prone to irritation,” the founder shares.

So, how can you safeguard your skin barrier? It’s easy. Do less.

For starters, cut down on cleansing. This will differ from person to person, but a deep cleanse is probably only necessary at night, and a splash of water will do just fine in the morning. “Cleansers that contain sulfates, which function as a kind of detergent, basically strip the skin of its oil. This can raise the pH and disrupt the skin barrier, making you more prone to acne and rosacea breakouts as well as eczema and irritation,” Dr. Geria warns. He says to skip “cleansers that foam and bubble” to be safe.

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“You do not want to exfoliate your skin more than one or two times a week, as this will strip away the oils from the skin and break down the skin barrier,” adds Dr. Icecreamwala. That means only one or two nights per week of exfoliating pads, acids, scrubs, chemical peels, or dermaplaning—no more than that, and no more than one at a time.

Preserving the stratum corneum is about more than just avoiding harsh products, though. It’s about avoiding too many products, even the supposedly nourishing ones. The more ingredients you put on your face, the more likely you are to disrupt the balance of your microbiome. “I recommend keeping your skincare routine simple and gentle,” Dr. Icecreamwala says. “You want to protect your skin barrier from UV rays by using sunscreen diligently, and I recommend moisturizing with products that contain ceramides to help maintain hydration within the skin barrier.”

When in doubt, reach for natural oils—preferably ones that are a close chemical match to human sebum, like jojoba and meadowfoam seed oils—to reinforce the lipid barrier. “Lipid-loving, oil-based products are key to maintaining the natural oils in your skin,” Caglia says.

Think of it this way: “If you take fish from the sea and put them into [fresh water], it would kill them. It’s the same for the bacteria we have on our skin,” says Sue Nabi, founder of vegan skincare line Orveda. “They need the biomimetic ceramides, sterols, and essential fatty acids. If these bacteria are living in an ocean made of silicones and mineral oil, it’s not their natural environment.”

On that note, supporting your skin’s natural sebum production is key, which is a matter of hormone health. Be extra cautious with treatments that target the sebaceous glands, like Accutane and certain lasers, as lowered sebum production can negatively impact the pH balance of the acid mantle over time. The same goes for products or prescriptions that are known to thin the skin barrier, like steroids and retinoids. While these ingredients may be helpful at easing symptoms in the short term, they have the capacity to compromise the stratum corneum in the long term.

You can also boost your skin barrier from the inside out.

So that lipid barrier that Dr. Geria mentioned? It’s made up of omega-3 and omega-6 fatty acids, which are considered “essential fatty acids” because they are essential to brain, heart, and skin health. But get this: The body can’t produce these omega fatty acids on its own. It needs to source them from your diet, which is where omega-rich foods and supplements come in. Nuts and seeds are excellent sources of omegas, as are salmon, sardines, spinach, and cod liver oil.

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There’s even evidence to suggest that the gut microbiome and the skin microbiome are “intertwined.” You can theoretically support your skin barrier by loading up on probiotics in the form of fermented foods—think yogurt, kimchi, sauerkraut, kefir, miso, and anything pickled. (Of course, probiotic supplements are always an option, too.) Pro tip: The skin microbiome may benefit from a topical application of probiotics, too. Try a 20-minute yogurt face mask or more conventional probiotic products, like the ones offered by Mother Dirt and Aurelia Probiotic Skincare.

Finally, don’t forget to get sweaty every once in a while. Sweat is an integral part of the acid mantle, after all.

With that, your skin will be as perfectly protected as the inside of an avocado—the way that nature intended.