What is the skin barrier?

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What is the skin barrier?

Function  |  Definition  |  Maintenance  |  Tips

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Written by Dr. Ian Harrison BSc, PhD with contributions from Dr. Niyati Sharma Credentials: MBBS, FACD, MPH.

Updated on December 06, 2023

The skin is the body’s largest organ. A well-known fact that most of us have heard at least once, be it at school or in a quiz of some kind. We all also know that the skin is important for things such as appearance, temperature regulation and, perhaps most importantly, protection. But what exactly do we mean by ‘protection’? That is where the skin’s barrier function comes in.

Function

What is the skin’s barrier function?

The skin’s barrier function relates to its ability to act as the body’s first line of defence to the outside world; keeping all the good things like moisture in and all the bad things like irritants and allergens out.

Rather than one simple layer, the skin is actually made up of three primary layers: the hypodermis (deepest layer), the dermis (middle layer) and the epidermis (upper layer). These layers are each made up of different sublayers, but it is one sublayer in particular that is crucial to the skin’s barrier function: the outermost layer of the epidermis, also called the stratum corneum.

The stratum corneum literally forms the protective barrier between the inner body and the outer world1; it is the vanguard that helps to keep us healthy and safe. The stratum corneum is made up of approximately 15-25 layers of dead skin cells, called corneocytes, embedded within a lipid bilayer2 which forms a sort of “brick and mortar” wall3.

The skin barrier is the outermost layer of your skin that serves as a protective shield. A healthy skin barrier helps protects against irritants and allergens.

Dr. Niyati Sharma

Definition

Understanding the skin barrier with Dr. Niyati Sharma

Understanding your skin can be overwhelming, with a lot to take in. We sat down with dermatologist Dr. Niyati Sharma to break down and simplify the science of the skin. In this series, you'll learn all about the skin barrier, what 'pH balanced' means, and the layers of your skin.

Watch our Science Says video to learn more with Dr. Niyati Sharma

Maintenance

Maintaining the skin’s barrier function

The proper functioning of the stratum corneum is crucial for the proper barrier function of the skin in general. If it is working correctly, things like allergens and irritants have a very hard time getting in, and important things like moisture have a hard time getting out. On the other hand, if the barrier isn’t working properly, moisture can escape, leading to dryness, and all those allergens and irritants can have a field day. To continue the brick wall analogy, if the bricks and mortar aren’t in prime condition, the wall isn’t going to be very effective if it starts crumbling.

A compromised barrier function, either through water loss or the entry of irritants or allergens in through the skin can not only lead to dryness, irritation and discomfort, but can worsen the symptoms of many skin conditions, including eczema4.

Tips

How to support my skin’s barrier function

Some general tips can help substantially, including:

  • Look for products that contain one or more efficacious moisturising ingredients. Humectants, such as glycerin, mimic the action of the skin’s Natural Moisturising Factor (NMF) to draw and hold water in the cells of the epidermis5.  Occludents, such as petrolatum, are oil-based and form a near-waterproof coating on the skin to reduce transepidermal water loss and increase skin hydration6. Lastly, emollients, such as dimethicone, mimic sebum to lubricate the skin and reduce dryness7. 
  • Avoid common skincare ingredients such as fragrance and colour, as these are well-known to cause irritation8,9. 
  • Avoid the sun where you can: UV radiation is a leading cause of skin damage, from premature ageing to cancer. When out and about, use a high SPF sunscreen, preferably with moisturising ingredients.

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References

1. Matsui T, Amagai M. Dissecting the formation, structure and barrier function of the stratum corneum. Int Immunol 2015;27(6):269–80.

2. Holbrook KA, Odland GF. Regional Differences in the Thickness (Cell Layers) of the Human Stratum Corneum: An Ultrastructural Analysis. J Invest Dermatol 1974;62(4):415–22.

3. Harding CR. The stratum corneum: structure and function in health and disease. Dermatol Ther 2004;17(s1):6–15.

4. Agrawal R, Woodfolk JA. Skin Barrier Defects in Atopic Dermatitis. Curr Allergy Asthma Rep 2014;14(5):433.

5. Greive K. Glycerine: the naturally effective humectant. Dermatol Nurs 2012;11(1):30–34.

6. Ghadially R, Halkier-Sorensen L, Elias PM. Effects of petrolatum on stratum corneum structure and function. Journal of the American Academy of Dermatology 1992;26(3):387–396.

7. Greive K. Cleansers and moisturisers: the basics. Wound Pract Res 2015;23(2):76.

8. Johansen J. Fragrance contact allergy: A clinical review. American Journal of Clinical Dermatology 2003;4(11):789–798.

9. Mayer RL. Aromatic Amines and Azo-Dyes in Allergy and Cancer. Journal of Investigative Dermatology 1948;10(5):389–96.