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Defining the skin barrier

Article-Defining the skin barrier

When explaining the skin barrier and its importance to patients, more help is needed from the industry. For instance, a simple “Got Milk?”-type slogan that makes you immediately think of the skin barrier has not yet emerged. Physicians and scientists need a straightforward way to describe the skin barrier without getting too technical.

As described by Alice Prethima Michael, M.D., founder and managing medical aesthetic physician at Ageless Medi Spa (Kuala Lumpur, Malaysia), “The skin barrier, or stratum corneum, is the outermost layer of the skin, which provides critical defensive functions, including protection against all sorts of damage such as pathogens, major temperature changes, etc.”

In addition, the skin barrier is the first line of defense against the penetration of ultraviolet light, filtering much of it before it reaches deeper into the skin, which is where most of the pigment or ‘melanin granules’ reside,” she continued. “Melanin is, in fact, only a second line of defense against ultraviolet rays. Overall, any kind of disease condition will only worsen if the skin barrier is not maintained.”

On a deeper level, the skin barrier is composed of two different structural components, stated Nantapat Supapannachart, M.D., a cosmetic dermatologist in Bangkok, Thailand. “The corneocyte and inter-corneocyte lipids are arranged together with the cells providing structural support and acting as a hydrating reservoir for adequate enzyme processes,” she explained.

“The lipid bi-layer, a thin polar membrane made of two layers of lipid molecules, provides the boundary between the hydrophobic and hydrophilic interface, which regulates what goes into and comes out of the skin,” Dr. Supapannachart added. “Disturbing the function of this layer can have a significant effect on skin quality.”

According to Joel Schlessinger, M.D., a cosmetic surgeon and dermatologist who runs the Advanced Skin Research Center in Omaha, Neb., “The skin barrier is the difference between healthy skin and damaged skin. It is probably something that most dermatologists don’t think about at all. However, the reality is that the skin barrier is a very important concept to articulate to patients.”

Many people have been schooled to understand that the skin has seven layers," stated William Philip Werschler, M.D., F.A.A.D., F.A.A.C.S., a dermatologist and assistant clinical professor of medicine/dermatology, at the University of Washington School of Medicine in Spokane, Wash. “However, this really only refers to that millimeter or so of thickness of the epidermis,” he said. 

“When we think of the skin, meaning we in the industry, what we are mostly thinking about mostly is the dermis and the collagen,” Dr. Werschler indicated. 

The skin has several functions, and the first is the skin barrier, said dermatologist Carl R. Thornfeldt, M.D., the developer and founder of Episciences, Inc. (Boise, Idaho).

“This permeability barrier keeps the aqueous internal environment protected from the dry external environment, which includes all the toxins and contaminants in our environment,” he expressed.

Armed with an anatomical and technical understanding of the skin barrier, practitioners must then find a straightforward way to describe it to patients without getting too scientific. Dr. Werschler thinks physicians should consider how they might explain the skin barrier to a child. “I use a simple brick and mortar analogy,” he described. “The bricks are the skin cells and the mortar holding them together is the intercellular cement substance. At the bottom of the barrier you have the retaining wall foundation, otherwise the bricks would fall apart.”

Furthermore, there are specialized structures in the epidermis, Dr. Werschler continued.

“Imagine every ten bricks or so you place a decorative brick. Those are the melanocytes,” he said. “Your pigmentation is in the epidermis, and you are constantly shedding your pigmentation, as well. In addition, you can also have pigmentation after injury.”

Another visual way to explain the skin barrier is to conjur up the image of a shield, said Peter Lio, M.D., a clinical assistant professor of dermatology & pediatrics at Northwestern University Feinberg School of Medicine, and founding director of the Chicago Integrative Eczema Center (Chicago, Ill.).

“Our skin is designed to protect us from things in the world. When it is healthy, it acts like a shield for our skin. If the skin barrier is not working correctly, your skin can become inflamed and uncomfortable,” he illuminated.

As tissue migrates to the surface it matures and differentiates to form a shield or a brick-and-mortar type of barrier, Dr. Thornfeldt agreed.

“It has lipids and oils in an exact ratio and specific oil groups are required for function in a precise pattern,” he said. “When the skin barrier is damaged, the three barrier oils – cholesterol, ceramides and free fatty acids – are the first things made by the body to repair itself. Notably, 50% of that has to be linoleic acid and there are some other fatty acids, as well.”

A key skin barrier function is the connection between cells within the stratum corneum and epidermis called “tight functions,” stated Nikolay Turovets, Ph.D., CEO of MediCell Technologies, LLC (Carlsbad, Calif.), a developer of stem cell- related therapies.

“The tight junctions are complex structures of very specific proteins and extracellular matrix molecules, produced by skin cells. If the connections are well-established, in other words there are no gaps between cells, then the skin will hold water and it will not be released by the skin,” he explained.

At the bottom of the epidermis, the dermal-epidermal junction (DEJ) is the tough layer between the epidermis and the underlying dermis. “It is made of collagen and gives us the strength to our skin, noted Dr. Werschler. “It is in that layer of the collagen that you have blood vessels, nerves and all the action of living tissue.”

On the other side of the DEJ, the basal or “basement layer” could be considered as the bricks sitting on top of the foundation. Those cells divide, and as they do, they move up to the skin’s surface to be shed.

Of all the damage possible to the skin barrier, at the top of the list is the environment, Dr. Prethima Michael said. “That is why we often see patients with photo-aging, which is characterized by wrinkles, pigmentation, rough skin and loss of skin tone. When accumulated in our bodies, environmental toxins, such as lead, can weaken the skin’s integrity, as well as promote darkening of the skin.”

In addition to the attacking environmental elements, infection can disturb the skin barrier, as well, Dr. Schlessinger indicated. For example, if a person ends up with a fungal infection, it can impair the skin barrier allowing bacteria to enter, which further impairs the skin barrier.

“What we have found is that with nearly every skin condition we deal with, from psoriasis, eczema to even poison ivy, the skin barrier ends up disturbed and bacteria swoops in and takes a further toll,” he said.

When that complex skin barrier requires protection, a wide range of products are at hand. According to Dr. Schlessinger, anything that improves the skin barrier is, by design, going to take into account a number of factors, the primary of which is moisture and any disease conditions that are impairing the barrier.

“That doesn’t mean that in order to improve the skin barrier you have to have creams,” he said. “Sometimes improving the skin barrier is nothing less than improving the biome on the skin, which is the collection of bacteria that is out of whack or in some way out of sync with a healthy skin barrier.”

There are many products that claim to address the skin barrier functions, so it can be overwhelming for both clinicians and patients, Dr. Lio admitted.

“Many people are interested in the ‘best’ moisturizer or barrier repair cream, but it is all relative to the indication,” he said. “A more apt analogy may be to cars; for example, a Ferrari might be the ‘best’ car by some measure, but if you are hauling a trailer, it would likely be among the worst. With moisturizers, we are blessed with a huge array of possibilities and formulations.”

Dr. Lio often meets patients that have tried several products and weren’t happy or experienced adverse reactions to them. “Part of my specialty is to read the skin and observe carefully so that I can pick a product that will meet patient needs, both in medical and cosmetic patients. I rely on over a dozen favorite products depending on the skin type, body location,
age, and type / severity of skin condition,” he said.

In Dr. Turovets’ experience, some skin moisturizers that claim to protect the skin from water loss and preserve the skin’s barrier actually provide only a masking effect. “After applying moisturizers on the skin, we may feel that it is hydrated, but that is nothing more than a feeling. Our actual skin barrier remains damaged and unrepaired.”

Worse yet, some skincare ingredients will actually harm rather than help repair the skin, Dr. Thornfeldt added. “It is the retinols, propylene glycols and lactic acid that damage the skin and activate varying degrees of inflammation. Physicians need to know about products that help repair and even optimize the skin barrier.”

“It is the retinols, propylene glycols and lactic acid that damage the skin and activate varying degrees of inflammation,” explained Dr. Thornfeldt. “Physicians need to know about products that help repair and even optimize the skin barrier.”

Only barrier balancing and repairing creams can genuinely help restore the skin barrier, Dr. Turovets concurred. “These creams restore barrier function by repairing cell membranes, and they may also contain ingredients, such as defensins that restore tight junctions,” he said.

Improving the skin barrier can be as simple as using the correct topical or oral antibiotic to reestablish the skin and its cohabitants, Dr. Schlessinger stated. “We see a lot of people walking around with a skin barrier that is disturbed, and via a simple regimen they could re-epithelize the skin and end up with a healthier and more robust epithelium.”

Most of the products traditionally used on the skin barrier have been abrasive in nature, expressed Dr. Werschler. “These include microdermabrasion, light chemical peels, alpha hydroxyl acids and RetinA to some degree. All of these have been designed to exfoliate the skin one way or another, to thin out the stratum corneum for a smoother, prettier air corneocyte interface, which makes the skin look healthy and glowing.”

Some available therapies make use of microneedling and infusion to perform pre- and post-procedure skincare treatments, Dr. Werschler stated.

“A more accurate term to use is diffusion rather than infusion. Developers should use a fixed depth and accurate delivery system. If an energy-based system is involved, then it may involve damage to the skin via laser or some other method to strip the skin and deliver products into the different layers of skin,” he explained.

“Energy-based systems work by damaging the skin barrier,” Dr. Thornfeldt said. The key with those systems is you want to deliver a lot of ingredients before inflammation in the skin kicks up. The problem with a lot of the nutrients you put into the barrier is that they are proinflammatory, so they accelerate the inflammation. The patient will get plumping for one or two days, or until the inflammation goes down. However, some of what you’ve put in there will also damage the skin and destroy the extra cellular matrix.”

Dermalinfusion from Envy Medical, Inc. (Long Beach, Calif.), is an example of such a product that applies an advanced, non-invasive skin resurfacing technology to perform exfoliation and extraction, as well as accommodate the infusion of condition-specific serums to improve skin health, function and appearance. This system offers customization features that result in immediately noticeable improvement in volume, hydration, tone and texture. As with other dermal infusion-type products, it can also be used in conjunction with other non- and minimally invasive procedures to enhance results.

Among other energy-based microneedling solutions, Secret RF from Cutera, Inc. (Brisbane, Calif.), is a novel fractional RF-based microneedling system for tissue coagulation and hemostasis, designed to stimulate and remodel collagen and address the common signs of aging. Secret RF delivers precise, controlled energy at various depths to target patients’ most common skin concerns – fine lines, wrinkles, scars, photo-aging and striae – on the face and body with limited-to-no downtime.

Similarly, Vivace RF from Aesthetics Biomedical, Inc. (Phoenix, Ariz.), combines targeted microneedling with RF-based energy to help stimulate and tighten the skin. The system reportedly minimizes the appearance of pores, fine lines and wrinkles; reduces secretion of skin oils (seborrhea); smooths scars; improves delivery and absorption of medical-grade skincare products; and reduces the occurrence of acne.

After any energy-based procedure, “You need to slam that skin barrier shut,” Dr. Thornfeldt continued. “Positive ways to accomplish this include skin preparation so that you have a consistent response. Two to four weeks before you do anything, you want to get the skin barrier in shape. Eliminate inflammation, decrease the microbes, get the biome back in
balance, etc. That will give you the best, most predictable result.”

When considering the side effects of using some energy-based systems for skin barrier work, Dr. Supapannachart was less encouraging. “Many of these devices rely on disrupting the skin barrier to create a wound that brings about new collagen formation,” she began.

“Examples of this technique include laser-based resurfacing, skin needling, plasma-based resurfacing and chemical peels.” The use of energy-based devices in particular can lead to post-inflammatory hyperpigmentation (PIH), which is a serious concern among Asian patients,” she continued. “Thus, in my region, machines that can deliver active ingredients into the skin without disrupting the skin barrier are more popular.”

Safer approaches, such as phonophoresis, electrophoresis and electroporation can temporarily increase the permeation of skin,” noted Dr. Supapannachart. “Exposing the skin to a light electrical field can reduce the cell wall’s resistance, rendering it more permeable. We can then transfer a wide range of naturally nurturing solutions or oils into the skin cells – a treatment that is painless with no side effects.”

Along those same lines, a popular approach among APAC-based practitioners utilizes oxygen jet technology. “It is basically a ‘pressure wash’ that uses water to deep clean by infusing saline and oxygen into the skin, which is ideal for treating acne and rosacea,” stated Dr. Supapannachart. “The procedure deep cleans pores and works to eradicate bacteria from underneath the skin.”

Dr. Prethima Michael has used this type of approach for around 15 years. “Oxygenation therapy produces micro molecules, which allows us to deliver vitamins or serums into the skin,” she said. “First, we clean the skin by way of cavitation and scaling, then we inject molecules deep into the skin. This helps to produce the fibroblasts that will contribute to repairing or rejuvenating the skin.”

Recently, Dr. Prethima Michael adopted a newer hydro-jet technology, which exfoliates the skin without the use of crystals or abrasive wands. “We can infuse the skin with a soft rubbing action applied simultaneously with the micro-jets, which carries the serums and vitamins into the skin,” she said.

What if you use an energy-based system that delivers product into the skin barrier, but the products have not been tested for internal use?

“We have seen this with microneedling, for instance, where there are punctures made within the skin and products are attempted to be introduced into these punctures. This is concerning and potentially harmful to the patient,” Dr. Schlessinger warned.

Unknown chemicals, formulations and preservatives, as well as many ingredients that are intended for topical use have not been tested for internal use, Dr. Schlessinger continued.

“There are risks associated with injecting substances into the skin without testing. Keep in mind there are certain skincare products that are perfectly safe to be internalized, but I’m less certain about introducing different fragrances or colors, and other components of skin creams,” Dr. Schlessinger said.

Mesotherapy can offer an effective system of delivery, but is more popular across Europe and Asia than the United States. “In certain countries, mesotherapy can be used to reduce fat as it contains bio salts and compounds that already exist in the skin, for normal skin structure. Those therapies do have measurable benefits,” stated Dr. Thornfeldt.

Dr. Schlessinger even noted the value of regenerative medicine to repair the skin barrier. “People use platelet-rich plasma (PRP), which is reintroducing your own autologous serum into yourself,” he said. “It may offer benefits, and it doesn’t seem to result in any harm. That is a lot different from compounding formulations like Minoxidil and then putting it into the skin via mesotherapy.”

Dr. Prethima Michael noted a recent focus on regenerative medical methods for the whole body, including attention to the skin barrier. “We can infuse the skin with growth factors and PRP via mesotherapy to increase the skin’s health.”

In addition to slowly emerging regenerative approaches, a few relevant skin rejuvenation technologies have entered the APAC marketplace in recent years. “I believe the newest is plasma technology, in which an ultra-high frequency (UHF) generator excites inert nitrogen gas, which is converted into activated ionized gas,” Dr. Supapannachart revealed. “This plasma-containing heat energy is directed to the skin via a handpiece equipped with a quartz nozzle tip.”

Specific to the APAC region, combination therapies that merge new and old approaches are likely to remain the norm when it comes to addressing the skin barrier. “We use multiple delivery systems and techniques to optimize results,” expressed Dr. Supapannachart. “For instance, we’ve applied emulsion infusion, micro-encapsulation, the molecular patch and nano technology to place substances under the skin. In addition, phospholipids, liposomes, microcapsules and hydrogels are all different molecules that allow active ingredients to bypass the outermost layers of the skin, which can provide better penetration.”

Unpredictable side effects are an overarching issue when using devices and infusion-style therapies to heal the skin barrier. In addition, most regulatory bodies, including the U.S. Food & Drug Administration, have offered no regulations or advice regarding anti-aging skincare and delivery systems, including microneedling and the wealth of cosmeceuticals that are routinely applied to the skin barrier.

“Thousands of cosmeceuticals have been tested in multiple clinical trials for customers or patients, but none of those trials deal with introducing cosmeceuticals into the skin or into the patient,” stated Dr. Schlessinger.

Cosmeceuticals do not exist in the eyes of the FDA, Dr. Werschler said. “The regulators should establish a third category of over-the-counter (OTC) skincare products that have limited effects, but the FDA will not do that. Unless you are a soap made from animal fat and lye, you are regulated by the FDA. For instance, Dial and Dove are considered OTC drugs because they are designed to affect the surface of the skin.”

However, some standards and methodologies do exist at the practice level. “Before a procedure, use a skin barrier renewal cream to ensure normalization of barrier functions; followed by a cleanser that would reduce the number of microbes on the skin; and then a rebalancing toner to obtain the proper pH,” Dr. Thornfeldt outlined. “I do this before a procedure to get a predictable result and minimize side effects.”

Under the current conditions, it is nearly impossible for the average patient to find the best method or approach to repairing the skin barrier. As such, “It is up to the practitioner to improve patient care and the health of peoples’ skin,” Dr. Thornfeldt advised. “We have the technology to do this and patients need to understand that, and search for products that work to control inflammation and optimize skin barrier function.”

Aesthetic practitioners and dermatologists must be clear and focused when approaching skin barrier repair, Dr. Supapannachart stated.

“In the aesthetic field, only by understanding the function of the skin barrier can we determine the best way to deliver active ingredients into the skin. In the dermatologic field, we should provide rational therapies that keep the skin in good shape and with good barrier reflex, which also addresses barrier-disrupted skin disease,” she concluded.