Here at CV Skinlabs, we’ve talked a lot about the skin’s outer barrier—the outer layer of skin that protects us from germs and environmental assaults, and that helps keep moisture trapped within the skin where it does the most good.
We’ve talked about keeping this outer barrier healthy and strong, and how things like sun exposure, environmental pollutants, harsh weather, poor diet, and low-quality skincare products can damage it, leaving you vulnerable to premature aging, dryness, fine lines and wrinkles, and infections.
You may imagine this skin barrier as a simple layer of skin that covers and protects the layers underneath. That’s a good way to envision it in general, but actually, the skin and its outer layer are much more complex.
In truth, that one outer barrier is made up of four barriers that help ensure protection from external harm:
- Physical barrier: Made up of the skin cells that preserve the structure of the skin, forming tight junctions and trapping moisture.
- Chemical barrier: Maintains the moisture and acid mantle of the skin, which helps inhibit the growth of bacteria.
- Microbiome barrier: A complex system of good and bad bacteria—similar to the microbiome in the gut—that helps keep dangerous microbes away while assisting the immune barrier.
- Immune barrier: Made up of immune cells that sense danger signals, protect against pathogens, and mount defenses when needed.
These four barriers work together to keep the skin and the body protected. Let’s look more closely at what each one does.
1. The Skin’s Physical Barrier
This is the barrier that you can see and touch. It provides the first line of defense against external threats. Formed by numerous layers of epidermal and dermal keratinocytes (types of skin cells), the outermost layer is called the “stratum corneum” and is composed of as many as 100 layers of keratinized cell envelopes (like scales, also called “corneocytes”) that together form a protective barrier all over the body.
This outer layer helps shield us from the environment, and though it absorbs some of what it comes into contact with, it also keeps much of it out. (Otherwise, you would drown while taking a bath!) The cells that form this outer layer are packed with keratin (a protein) and are tightly connected. These are also the “dead” cells that are frequently shed to make room for newer cells underneath to emerge.
Keeping the physical barrier healthy and strong helps provide that tough physical armor that you need to not only stay well but to enjoy smooth, soft skin. Whenever the outer, physical barrier is compromised, the skin suffers. Signs of problems in this barrier include:
- Skin infections and irritation
- Dry skin
- Cracked skin
- Bleeding skin
- Rough skin
- Fine lines and wrinkles
- Sagging and bagging
2. The Skin’s Chemical Barrier
The chemical barrier is formed by lipids and acids, including skin sebum (oil produced by the sebaceous glands), sweat, lactic acid, and fatty acids. It helps maintain the moisture and acid mantle of the skin.
The acid mantle is a fine, slightly acidic film on the surface of the skin that repels bacteria, allergens, and other potential contaminants. At the same time, it keeps moisture and nutrients in so the skin stays soft and supple.
This protective barrier also contains acids and proteins with antimicrobial properties that shield against fungi, bacteria, viruses and other icky things that can penetrate the skin. If this barrier is disrupted or damaged, the skin becomes more vulnerable to damage and infection. Signs of problems in this barrier include:
- Dryness
- Flaking
- Redness
- Sensitivity
- Acne breakouts
3. The Skin’s Microbiome Barrier
You’ve probably heard about the microbiome in your gut—the community of good and bad bacteria that when healthy, promotes good digestion and a strong immune system.
Your skin has the same type of bacterial community. It’s sort of unsettling to imagine, but your skin is colonized by millions of bacteria, with studies finding different species in different areas of the skin. Though bacteria are the most abundant organisms found on the skin, numerous fungi and viruses are there, too.
All of these organisms have adapted to enjoy life on the skin, which means they don’t want other organisms invading their space. Many of them produce molecules that inhibit the colonization of other microorganisms or alter their behavior. These organisms also play a role in educating the immune system and helping it to protect the skin from invaders.
Scientists have also found that the skin and gut play a balancing act between beneficial and harmful microbes, consistently working to maintain a healthy state. Though we are still learning about this fascinating barrier, we know that If the balance of the microbiome is damaged, the following problems may occur:
- Atopic dermatitis
- Eczema
- Acne
- Rosacea
4. The Skin’s Immune Barrier
The immune barrier in the skin works as it does in the body. Its main job is to protect from invasion by unfriendly microbes. It consists of cells that sense danger signals and recruit more cells to any site that is under threat. When you scratch yourself and the area turns red and swells up, that’s a sign the immune system is working to get rid of any bugs and help the area heal. Inflammation is the immune system’s primary weapon against dangerous pathogens, so whenever you see that red, swollen reaction, that’s the immune system going to work.
If the physical and chemical barriers in the skin fail—say, you cut yourself or you’re exposed to a toxic chemical—it’s then up to the immune and microbiome barriers to protect you. This is when these cells rush to your defense, recognizing the invaders, sending messages about them, recruiting new cells to fight them, and eventually eradicating them. This is a key process in protecting you from infections as well as illnesses. It’s also important in helping the skin heal from any injuries.
The immune system sometimes reacts by mistake, however, identifying harmless microbes as dangerous and mounting a defense. This occurs when the skin reacts to an ingredient in a skincare product, for example, or to an allergen.
Signs of problems with the immune barrier include:
- Skin allergies
- Hypersensitivity
- Skin reactions, hives, redness, swelling
- Psoriasis (an autoimmune disease)
- Acne
- Rosacea
How to Care for the Skin’s 4 Barriers
Now you have an idea of how much the skin is doing every day to protect you! It may all sound a bit complex, and it is, but you don’t have to remember all the details. By following these tips, you can help keep all the barriers working optimally, so skin looks and feels its best.
- Avoid harsh soaps: These can disrupt the acid mantle and strip the skin of its good bacteria, upsetting at least two barriers. Cleanse only twice a day with a gentle, moisturizing, and pH-balanced cleanser.
- Moisturize: A lack of moisture damages the physical and chemical barriers, and can lead to an imbalance of the microbiome too. Look for moisturizers with ceramides or natural oils, which are fats that restore the skin barrier, as well as hyaluronic acid or glycerin, which draw moisture into the skin. Then be sure to moisturize immediately after washing. Make sure you’re drinking water, too—the skin needs that moisture from the inside, out.
- Eat a healthy diet: Your skin, like the rest of your body, needs a variety of nutrients to support barrier function. Make sure you’re regularly eating enough fruits and vegetables, lean proteins, healthy fats, and whole grains.
- Use skin-friendly products: Many over-the-counter skincare products are filled with harsh and toxic chemicals that damage all of the skin’s barriers. Check out our list of ingredients to avoid, then choose products from conscientious companies that use natural and organic ingredients that are good for the skin.
- Reduce inflammation: If you’re struggling with acne, rosacea, eczema, or other skin conditions involving an over-reaction of the immune system, take steps to reduce that inflammation. Stop using any harsh or aggressive products (like retinols and exfoliating acids) and treat your skin to calming ingredients like oats, shea butter, natural oils, and extracts known to calm the skin. Note: All of our CV Skinlabs products are made to reduce inflammation, with ingredients like beta-glucan (from oats), calendula, valerian, comfrey, aloe, and more.
Have you struggled with malfunctioning skin barriers?
