Lipid Barrier - Beneficial Fats in The Skin Barrier

Posted by Dr. Natasha Ryz on

The lipid barrier of the skin barrier is made of beneficial fats.

This article will discuss:

    • What are beneficial fats?
    • What is the skin barrier?
    • What is the stratum corneum? "The brick wall"
    • What is the stratum corneum made of?
    • Lipids "the mortar that holds the bricks together"
    • Free fatty acids in the stratum corneum
    • What is the dermis made of?
    • What is sebum?
    • Summary
    • References

Lipid Barrier - Beneficial Fats in The Skin Barrier

What are beneficial fats?

There are many beneficial fats and lipids that are naturally found in the lipid barrier and skin barrier and play a critical role in keeping your skin healthy.

The surface of your skin is covered by a layer of protective fats, including epidermal lipids and sebum.

Epidermal lipids are released from keratinocytes (skin cells), and are a mixture of ceramides, free fatty acids and cholesterol. These lipids are released from skin cells and fill the spaces between the cells, like mortar or cement (Pappas, 2009).

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). 

Beneficial fats and lipids help to lubricate and coat your skin cells and, nourish your skin.

Beneficial lipids:

  • Strengthen the skin barrier.
  • Improve the appearance of skin.
  • Make skin feel soft and smooth.
  • Reduce the appearance of fine lines and wrinkles.
  • Relieve dry skin, flaking and scaling.
  • Reduce redness and inflammation.
Lipid Barrier - Beneficial Fats in The Skin Barrier

What is the skin barrier?

The skin barrier includes the outermost layers of skin, called the stratum corneum.

Your skin barrier is essentially what you can see and touch on the surface of your body.

When your skin barrier is healthy, it feels and appears smooth, soft, and plump.

In contrast, a damaged skin barrier looks dry, rough, dull, and dehydrated, and may become irritated and inflamed.

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.

Learn More: What is The Skin Barrier?

Lipid Barrier - Beneficial Fats in The Skin Barrier

What is 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.

Lipid Barrier - Beneficial Fats in The Skin Barrier

What is the stratum corneum made of?

On a weight basis, the stratum corneum contains approximately 70% protein, 15-25% water and 15% lipids (Ananthapadmanabhan et al, 2013).

The structure of the stratum corneum can be described as a ‘brick and mortar’ model, in which the protein-rich corneocytes are the bricks, and the mortar is the lipid‐rich matrix containing ceramides, cholesterol, and fatty acids.

Lipid Barrier - Beneficial Fats in The Skin Barrier

Lipids "the mortar that holds the bricks together"

Epidermal lipids are are a mixture of ceramides, free fatty acids and cholesterol. These lipids are released from 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).

Lipid Barrier - Beneficial Fats in The Skin Barrier

Free fatty acids in the stratum corneum

The main free fatty acids in the lamellar membranes are:

  • 10% palmitic acid (C16:0)
  • 10% stearic acid (C18:0)
  • 15% behenic acid (C22:0)
  • 25% lignoceric acid (C24:0)
  • 10% hexacosanoic acid (C26:0)

(Kang et al, 2006; Lin et al, 2017).

Other free fatty acids that are also found naturally in the stratum corneum include:

  • oleic acid (C18:1, n-9)
  • eicosapentaenoic acid (C20:5, n-3)
  • arachidonic acid (C20:4, n-6)
  • docosahexaenoic acid (C22:6, n-3)
  • linoleic acid (C18:2, n-6)
  • α-linolenic acid (C18:3, n-3)
  • γ-linolenic acid (C18:3, n-6) 
  • dihomo-γ-linolenic acid (C20:3, n-6)

(Lin et al, 2017).

Linoleic acid 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

What is the dermis made of?

The dermis is the middle layer of skin, and is composed of a thick layer of dense connective tissue.

The dermis also contains hair follicles, sweat glands, and oil-producing glands called sebaceous glands, that produce sebum.

What is sebum?

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). 

Lipid Barrier - Beneficial Fats in The Skin Barrier

Summary

What is the lipid barrier?

The surface of your skin is covered by a layer of beneficial fats, including epidermal lipids and sebum.

Epidermal lipids are released from keratinocytes (skin cells), and are a mixture of ceramides, free fatty acids and cholesterol. These lipids are released from skin cells and fill the spaces between the cells, like mortar or cement.

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.

These natural fats and lipids help to lubricate and coat your skin cells and, nourish your skin.

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. 

Downing, D.T., Strauss, J.S. and Pochi, P.E. Variability in the chemical composition of human skin surface lipids. J. Invest. Dermatol. 53, 322–327 (1969).

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.

Pappas A. Epidermal surface lipids. Dermatoendocrinol. 2009 Mar;1(2):72-6.

Verdier-Sévrain et al. (2007). Skin hydration: a review on its molecular mechanisms. Journal of Cosmetic Dermatology, 6, 75–82.

Dry Skin Skin Barrier Skin Science

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