Article Summary

The stratum corneum
A perfect design
Do’s and don’ts
Corneotherapy

TikTok is full of videos on how to fix a damaged skin barrier and there’s countless Google search results on what the skin barrier is. But a decade ago, the term “skin barrier” probably wasn’t even on your radar - much less one of the marketing claims being touted on every new moisturizer launch. In this article, we’re stripping down the topic of barrier repair to what you actually need to know about your skin barrier and how to keep it healthy.

Meet the Stratum Corneum AKA the Skin Barrier

Before we zoom in on the skin barrier, it’s important to have a general sense of how our skin is structured. The skin is basically a protective covering that encases the entire body and acts as a shield against our environment. It’s split into two regions, the dermis (the deeper layer) and the epidermis (the upper layer). Below our skin, we have a subcutaneous layer that’s composed of fat and then there’s fascia, muscle, and then either bone or organ.

The epidermis is where the skin barrier is found and this region of the skin is a busy one as the cells there are rapidly dividing and growing. At the bottom layer of the epidermis (the stratum basale), epidermal stem cells divide and create new cells. This in turn pushes the cells above them upwards and the cells continue to move upwards through the epidermis as this process repeats. The cells change depending on what layer they’re in and keratinocytes eventually become flat, dead cells called corneocytes.

The stratum corneum is the top layer of the epidermis and what we call the skin barrier - it’s what you can actually see with the naked eye when you look at your skin. In between skin cells called corneocytes, lipids fill in the gaps and form a tight, waterproof seal. You’ll often hear the skin barrier described as a “brick wall” with the skin cells being the “brick” and the lipids as the “mortar.” This is a helpful visual to keep in mind as we discuss the skin barrier.

Like the skin, the skin barrier’s job is to act as a protective shield. It keeps water in so that the skin can function properly and remain healthy. And it keeps everything out that could harm us - like germs, sunlight, and allergens. While the skin cells of the skin barrier may technically be dead, don’t be fooled into thinking we don’t need them.

The Skin Barrier’s Perfect Design

There is no better engineer than nature and the skin barrier perfectly illustrates that. Every little detail has been thought of and when it’s healthy, it functions flawlessly. As I mentioned before, to understand the skin barrier you need to understand the skin. And everything that is happening within our skin barrier all starts with the layer underneath it... the stratum granulosum.

Think of the stratum granulosum as the prep shift at a restaurant. We’ve got prep cooks called lamellar granules hard at work preparing the ceramides and fatty acids that will be used to make up the lipid matrix we discussed - like the ingredients for the night’s entrees. We also have other “ingredients” being prepped - skin cells called keratinocytes have been slowly flattening and filling with keratin so they can become corneocytes and the lamellar granules are also making the enzymes that the skin will later use to shed these skin cells when they reach the end of their life cycle. In order for our restaurant to be successful (so our skin barrier in this analogy), the preparation needs to be completed.

Once all the “ingredients” make it to the final skin layer, they’re immediately utilized. Corneocytes not only contain keratin for water proofing but they also have a mixture of humectants within them that work with skin lipids to keep moisture in our skin. Meanwhile, our lipid “mortar” is composed of ceramides, cholesterol, and fatty acids and needs to be correctly “stocked” with the right number and position or the skin barrier can’t function correctly. Every piece of the skin barrier works together as a team and skin disorders or stressors that reduce skin lipids or influence the shape of skin cells will impact barrier function. Every aspect of the skin barrier is designed to work together.

But it’s not the structure of the skin barrier that makes it brilliant. It’s the layers and layers of protection built within it.

Barriers within the Skin Barrier

Antimicrobial Barrier. Antimicrobial peptides called defensins and the immune system work together to protect our skin.
Photoprotective Barrier. While not sufficient to replace sunscreen these days, melanin within this barrier helps protect the skin from UV exposure.
Antioxidant Barrier. Endogenous Vitamin C and antioxidant defenses help protect our skin against oxidative stress generated from our environment.

Moisture Barrier. The bricks and mortar structure of our skin barrier keeps moisture in with cell junctions tightly anchoring cells together and the lipids filling in the gaps.

Do’s and Don’ts of Skin Barrier Health

The skin barrier is integral to skin health but it’s easy to get excited when you first learn about it and get carried away. Most people don’t need a bunch of products with barrier repair claims and being a little dry or irritated doesn’t automatically mean you’ve damaged your skin barrier. Let’s discuss how to care for the skin without going overboard.

Protecting Your Barrier

Use gentle, skin friendly cleansers
Avoid over cleansing or excessive exfoliation
Skip products that are highly alkaline or harsh like soaps and baking soda
Use a well formulated moisturizer for your skin type
Consider a humidifier when the air is low in humidity
Limit too many long, hot baths and showers
Skin that is under stress like acne prone skin or anyone starting a retinoid may want to consider barrier therapy
Avoid treatments like microdermabrasion that remove the skin barrier while offering minimal benefits

Anyone can care for their skin barrier, you don’t need to be a sensitive skin type or wait until there’s signs of barrier impairment. Our skin barrier offers an invaluable defense against the outside world so a barrier friendly routine helps support that and keep the skin healthy. Adopting a routine that respects barrier health is a good idea for everyone.

While it’s important not to automatically assume you have a damaged barrier, it does happen. We’re human and can sometimes fall into the trap of over exfoliating or being a little too liberal with that new retinoid. It could also be something outside of our hands entirely like weather or medications. Let’s talk about how to identify possible signs and what to do.

Signs of a Damaged Barrier

Dull or flaky skin
Tight, shiny appearance
Irritation or increased skin allergy
Stinging when applying mild products
Skin feel uncomfortable after cleansing
Always needing to apply moisturizer but effects feel temporary

Important: Because the primary job of the skin barrier is to keep in moisture, an increase in water loss is a sign of potential impairment and this immediately sends a signal for repair. In most cases, the skin will repair itself without any intervention and experiencing anything on this list doesn’t mean that you need to take any action. It’s only when these signs are persistent and not resolving on their own that you want to start looking at barrier therapy.

Damaged Barrier Rehab

Pause all retinoids, exfoliants, or anything potentially irritating.
Strip down your routine to just a few gentle products (cleanser, moisturizer, sunscreen for daytime, soothing serum) to reduce further irritation.
Petrolatum is your friend. It shouldn’t sting and will protect and restore the skin barrier while allowing the skin to rehydrate itself.
Protect your skin with sunscreen and avoid sun when possible as a compromised barrier can cause sun sensitivity.
Wait till skin is fully healed to reintroduce the rest of your routine.

Here’s some of my favorite Stratia Skin Products to support the skin barrier.

Velvet Cleansing Milk. This uses a mild cleansing agent that won’t disrupt the cohesion of the lipid matrix while a low pH preserves skin surface acidity for optimal barrier function. Glycerin, chamomile, allantoin, and aloe reduce irritancy from cleansing.
Rewind Serum. Niacinamide is a multitasking ingredient shown to increase the production of skin barrier components like ceramides, improving barrier function as a result. Skin soothers centella asiatica and panthenol as well as hydrators glycerin and sodium hyaluronate also address the irritation and dehydration associated with barrier impairment.
Lipid Gold Barrier Lotion. A constant in my skincare routine since its creation, this highly potent lotion uses a highly concentrated blend of ceramides, fatty acids, and cholesterol capable of actually replenishing barrier lipids and the functioning of the skin barrier. For significant barrier impairment, the concentration and number of lipids are key and this delivers.

Corneotherapy

Dr. Albert Kligman is considered by many as the godfather of dermatology and his research on tretinoin has left its mark on the field of skincare. He’s also a highly controversial figure, conducting studies on prisoners during a time where we didn’t have protections in place for the subjects being used for research. But what is less discussed is his research on moisturizers - which after his death, would be used to form the basis of corneotherapy.

“Corneotherapy is a remedial skin treatment methodology with its core principle being the repair and maintenance of the skin barrier defense systems.” Corneotherapy.org

Corneotherapy is an approach to skincare that prioritizes the health of the skin barrier, both in terms of your general skincare routine and in-office treatments. While an experienced corneotherapist will go beyond barrier repair and also seek to replenish the extracellular matrix of the skin and regenerate connective tissue, anyone can utilize the basic principles of barrier therapy for happier, calmer skin at home.

Taking a skin barrier focused approach can feel counterintuitive at first because it really challenges some of our long held beliefs around skincare. In our teens, many of us used drugstore acne products that dried out our skin and there was a lot of messaging around getting our skin to “behave.” Even today, there is a heavy focus on exfoliating away dead skin so skincare can work better. But barrier therapy is about instead assisting the skin in doing what it’s designed to and adding back what it’s missing.

I wanted to close this blog discussing corneotherapy to really stress the importance of a functioning barrier and that there’s science here. Social media can easily lead you to believe that the skin barrier is something to be exfoliated away - that we need to remove these “dead” skin cells to reveal fresh new cells for smooth, healthy skin. It doesn’t stop at skincare products, professional treatments like dermaplaning and microdermabrasion capitalize off this as well. Exfoliation can have its benefits, just don’t neglect your barrier or fall into the “the more the better” trap.

Mira is a skincare educator, blogger, and the content creator behind Skin Science by Mira and The Skincare Forum on Facebook. While skincare keeps her busy, she’s also pursuing her degree in Nursing and loves to spend her free time hiking. As a content writer for Stratia Skin, Mira shares her evidence-based approach to skincare topics and a passion for making science accessible.

Skin Barrier 101