Do you know the secret to healthy, radiant skin? It's all about your skin barrier!
When your skin barrier is healthy, your skin feels smooth, soft, and plump.
But when your skin barrier is damaged, your skin looks dry, rough, dull, and dehydrated, and may become irritated and inflamed.
To maintain a healthy skin barrier, it's crucial to consider the three main components that make up the barrier: the moisture barrier, lipid barrier, and acid mantle.
These three components work together to protect the skin from external aggressors and maintain optimal skin health.
This article will discuss:
- What is the skin barrier?
- The stratum corneum "The brick wall"
- What is the moisture barrier?
- What are natural moisturizing factors?
- What is the lipid barrier?
- Epidermal lipids in the lipid barrier
- Free fatty acids in the lipid barrier
- Sebum in the lipid barrier
- What is the acid mantle?
- Summary
- References
What is the skin barrier?
The skin barrier is essentially what you can see and touch on the surface of your body.
The skin barrier is made up of several layers, including the outermost layer called the stratum corneum, which is responsible for preventing water loss and protecting the skin from external stressors.
Your skin barrier includes:
- The moisture barrier
- The lipid barrier
- The acid mantle
The health and integrity of the skin barrier is crucial in maintaining healthy skin.
A healthy skin barrier appears smooth, soft, and plump to the touch and is essential in maintaining the skin's moisture balance.
In contrast, a damaged skin barrier appears dry, rough, and dull, and is more prone to irritation and inflammation.
Our skin is the primary barrier from the outside environment- it protects us from injury, water loss, UV radiation and invasion from microbes and toxins.
The skin barrier plays important roles in dry skin, acne, skin aging, dermatitis, psoriasis and atopic dermatitis, and is the subject of intense research.
The stratum corneum "The brick wall"
The stratum corneum is the most outer layer of the skin.
The stratum corneum can be thought of as a brick wall that protects you.
The "bricks" are the skin cells, called corneocytes, and the "mortar" that holds the bricks together is the lipids or fats, that together create the outer barrier.
The stratum corneum is the most outer layer of the epidermis and is the layer directly exposed to the external environment.
There are approximately 15 to 30 layers of corneocytes in the stratum corneum.
Learn more: What is the Stratum Corneum?
Corneocytes are regularly replaced through desquamation and renewal from lower epidermal layers, making them an essential part of the skin barrier property.
Desquamation is the natural process of shedding skin cells.
New skin cells are formed at the base layer of the skin, and they differentiate and migrate towards the skin surface, in a process that takes approximately 30 days. Nearly a billion cells are lost each day from the surface of adult skin (Milstone et al, 2004).
What is the moisture barrier?
The skin's moisture barrier is a part of your skin barrier.
Water is essential for the normal functioning of the skin.
The water content of skin is remarkably high - the epidermis (the outer skin layer) contains more than 70% water, while its outermost layer, the stratum corneum has been shown to contain ~15 - 25% water (Warner et al, 1988; Caspers et al, 2001; Caspers et al, 2003).
- it maintains plasticity of the skin, protecting it from damage
- it contributes to optimum stratum corneum barrier function
- it allows hydrolytic enzymes to function in the process of desquamation
When the water content of the stratum corneum falls below 10%, scaling on the skin surface becomes visible (Rycroft, 1985).
The retention of water in the skin is dependent on:
- Natural moisturizing factors (NMFs) and other humectants (such as glycerol and hyaluronic acid) to attract and hold onto moisture
- Intercellular lipids (fats) that form a barrier to prevent transepidermal water loss (TEWL) (Verdier-Sévrain et al, 2007).
Learn more: What is The Skin's Moisture Barrier?
What are natural moisturizing factors?
Natural moisturizing factors are a mix of humectants or hydroscopic molecules that help attract and hold onto water and maintain hydration in the skin.
Natural moisturizing factors include amino acids and their derivatives (pyrrolidone carboxylic acid and urocanic acid) made from the breakdown of epidermal filaggrin. Other components found within but also external to the corneocytes include lactates, urea, and electrolytes (Table 1).
Natural moisturizing factors are present in high concentrations within corneocytes and represent up to 20% to 30% of the dry weight of the outer skin layer (Verdier-Sévrain et al, 2007).
Proper hydration of the skin is required for maintaining the aesthetic properties of skin, such as moisturization, softness, smoothness, lack of flaking, etc.
Furthermore, proper hydration of the stratum corneum is also necessary for the critical processes of lipid biosynthesis, desquamation and natural moisturizing factor (NMF) production, that take place within these non-living, yet biochemically active, layers of the skin (Loden et al, 2001; Harding et al, 2004; Feingold et al, 2007; Bowser et al, 1986).
What is the lipid barrier?
Your lipid barrier is a part of your skin barrier.
The surface of your skin is covered by a layer of protective fats, including epidermal lipids and sebum.
- Epidermal lipids include:
- Ceramides
- Free fatty acids
- Cholesterol
- Sebum is made of:
- Triglycerides
- Wax esters
- Squalene
Theses beneficial fats and lipids are naturally found in the lipid barrier and skin barrier and play a critical role in keeping your skin healthy.
Learn more: What is the Lipid Barrier?
Epidermal lipids in the lipid barrier
The surface of your skin is covered by a layer of protective fats, including epidermal lipids.
Epidermal lipids are released from keratinocytes (skin cells) and fill the spaces between the cells, like mortar or cement (Pappas, 2009).
The stratum corneum lipids consist of an equimolar mixture of ceramides (45–50% by weight), cholesterol (20–25%), and free fatty acids (10-15%), with lower quantities of cholesterol sulfate and nonpolar lipids (Verdier-Sévrain et al, 2007).
Free fatty acids in the lipid barrier
The main free fatty acids in the lamellar membranes are palmitic acid, stearic acid, behenic acid, lignoceric acid and hexacosanoic acid (Kang et al, 2006; Lin et al, 2017).
Other free fatty acids that are also found naturally in the stratum corneum include oleic acid, eicosapentaenoic acid, arachidonic acid, docosahexaenoic acid, linoleic acid as well as its derivatives of linolenic acids [α-linolenic acid (C18:3, n-3), γ-linolenic acid (C18:3, n-6) and dihomo-γ-linolenic acid (C20:3, n-6)] (Lin et al, 2017).
Learn more: Beneficial Fats Found Naturally in The Skin Barrier
Linoleic acid (n-6) is the most abundant polyunsaturated fatty acid in the skin barrier (Ansari et al, 1970).
Most of the free fatty acids can by synthesized by the keratinocytes and are released into the stratum corneum.
However, linoleic acid and arachidonic acid are essential fatty acids that must be provided externally through diet, supplements or topically through skincare products (Lin at al, 2017).
Learn more: What is Linoleic Acid? Omega 6 Essential Fatty Acid for Dry Skin
Sebum in the lipid barrier
Sebum is an oily, waxy substance produced by your body’s sebaceous glands and eventually released to the surface of the skin. Sebum is primarily made up of non-polar lipids as triglycerides, wax esters and squalene. Sebum coats the skin, seals in moisture, and protects your skin from getting too dry (Pappas, 2009).
The composition of human sebum collected from the skin surface is typically 1.4% cholesterol, 16% fatty acids, 40% triglycerides, 25% wax monoesters, 2% cholesterol esters and 12% squalene (Downing et al, 1969).
What is the acid mantle?
Your acid mantle is a part of your skin barrier.
Your skin's acid mantle describes the inherent acidic nature of the outer skin barrier, also known as the stratum corneum.
The pH of the skin barrier is slightly acidic, in the range 4.5 to 6.5.
A proper skin pH is important to maintain healthy skin.
Your skin pH influences:
- Skin barrier function
- Desquamation or shedding of skin cells
- Protection against pathogens "bad bacteria"
Many factors can affect the pH of the skin, including age, sebum, sweat, detergents, cosmetics, and irritation.
Soaps and cleansers that are high in pH should be avoided, as high pH soaps can irritate and disrupt the skin barrier.
Summary
The skin barrier includes the outermost layers of skin, which is called the stratum corneum.
Your skin serves as the first line of defense against external threats, such as harmful microbes, toxins, and environmental stressors. Its protective function is largely attributed to the skin barrier, which is composed of three vital components: the moisture barrier, the lipid barrier, and the acid mantle.
The moisture barrier helps to prevent water loss and maintains adequate hydration levels, while the lipid barrier, consisting of oils and fats, acts as a protective barrier against external irritants and helps to keep the skin supple and moisturized. The acid mantle, a thin, slightly acidic film on the skin's surface, helps to regulate its pH and inhibit the growth of harmful bacteria and fungi.
A healthy skin barrier is crucial in maintaining skin health and preventing common skin conditions such as dryness, acne, dermatitis, psoriasis, and atopic dermatitis. As such, there is a growing body of research dedicated to understanding the mechanisms underlying the skin barrier function and identifying ways to enhance it.
Protecting and strengthening your skin barrier involves incorporating effective skincare practices, such as gentle cleansing, moisturizing, and using sunscreen, into your daily routine.
References:
Ananthapadmanabhan KP, Mukherjee S, Chandar P. Stratum corneum fatty acids: their critical role in preserving barrier integrity during cleansing. Int J Cosmet Sci. 2013 Aug;35(4):337-45.
Ansari, M.N.; Nicolaides, N.; Fu, H.C. Fatty acid composition of the living layer and stratum corneum lipids of human sole skin epidermis. Lipids 1970, 5, 838–845.
Bowser, P., White, R. and Nugteren, D. Location and nature of the epidermal per-meability barrier. Int. J. Cosmet. Sci.8, 125–134 (1986).
Caspers PJ, Lucassen GW, Carter EA et al. In vivo confocal Raman microspectroscopy of the skin: noninvasive determination of molecular concentration profiles. J Invest Dermatol 2001; 116:434– 42.
Caspers PJ, Lucassen GW, Puppels GJ. Combined in vivo confocal Raman spectroscopy and confocal microscopy of human skin. Biophys J 2003 July; 85: 572-80.
Feingold, K.R. Thematic review series: skin lipids: the role of epidermal lipids in cutaneous permeability barrier homeostasis. J. Lipid Res.48, 2531–2546 (2007).
Harding, C.R. The stratum corneum: structure and function in health and disease. Dermatol. Ther.17(suppl 1), 615 (2004).
Kang, L.; Ho, P.C.; Chan, S.Y. Interactions between a skin penetration enhancer and the main components of human stratum corneum lipids. J. Therm. Anal. Calorim. 2006, 83, 27–30.
Lin TK, Zhong L, Santiago JL. Anti-Inflammatory and Skin Barrier Repair Effects of Topical Application of Some Plant Oils. Int J Mol Sci. 2017 Dec 27;19(1):70.
Loden, M. Skin barrier function: effects of moisturizers. Allured’s Cosmet. Toiletries. 116,31–36 (2001).
Milstone LM. Epidermal desquamation. J Dermatol Sci. 2004 Dec;36(3):131-40.
Pappas A. Epidermal surface lipids. Dermatoendocrinol. 2009 Mar;1(2):72-6.
Rycroft RJ. Low humidity and microtrauma. Am J Ind Med 1985; 8:371–3.
Verdier-Sévrain et al. (2007). Skin hydration: a review on its molecular mechanisms. Journal of Cosmetic Dermatology, 6, 75–82.
Author Information
Dr. Natasha Ryz is a scientist, skin care expert and an entrepreneur. She is the founder of Dry Skin Love Skincare, and she creates skincare products for beauty, dry skin and pain relief.
Dr. Ryz has a PhD in Experimental Medicine from the University of British Columbia in Vancouver, and she is a Vanier scholar. She also holds a Master of Science degree and a Bachelor of Science degree from the University of Manitoba in Winnipeg.
Natasha is the former Chief Science Officer of Zenabis Global, and she oversaw extraction, analytics, and product development. Her team brought 20 products to market including oils, sprays, vapes and softgels.
Why I Started A Skincare Company