Skin Moisture Barrier - What Is It?

Posted by Dr. Natasha Ryz on

Skin Moisture Barrier - What Is It?

The skin moisture barrier is a part of your skin barrier. 

The skin moisture barrier ensures your skin is hydrated by trapping and holding water into your skin.

This article will discuss:

    • What is the skin barrier?
    • What is the stratum corneum? "The brick wall"
    • What is the stratum corneum made of?
    • What is the moisture barrier?
    • Normal skin hydration
    • Water and skin cell turnover
    • What are natural moisturizing factors (NMFs)?
    • What is hyaluronic acid?
    • What is glycerol?
    • Summary
    • References

Skin Moisture Barrier - What Is It?

What is the skin barrier?

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

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

The skin barrier protects you from physical, chemical, and microbial insults, and prevents the loss of water from 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.

Learn More: What is The Skin Barrier?

Skin Moisture Barrier - What Is It?

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.

 Skin Moisture Barrier - What Is It?

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.

Learn more: Lipid Barrier - Beneficial Fats in The Skin Barrier

Skin Moisture Barrier - What Is It?

What is the moisture barrier?

The skin moisture barrier is a part of your skin barrier. 

The skin moisture barrier ensures your skin is hydrated by trapping and holding water into your skin.

The skin moisture barrier is composed of water, natural moisturizing factors (NMFs) and other humectants, such as glycerol and hyaluronic acid to attract and hold onto moisture.

Normal skin hydration

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).

Adequate hydration of the stratum corneum serves three major functions (Fowler, 2012):
  1. it maintains plasticity of the skin, protecting it from damage
  2. it contributes to optimum stratum corneum barrier function
  3. 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:
  1. Natural moisturizing factors (NMFs) and other humectants (such as glycerol and hyaluronic acid) to attract and hold onto moisture
  2. Intercellular lipids (fats) that form a barrier to prevent transepidermal water loss (TEWL) (Verdier-Sévrain et al, 2007). 

Skin Moisture Barrier - What Is It?

Water and skin cell turnover

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 4 weeks. Nearly a billion cells are lost each day from the surface of adult skin (Milstone et al, 2004). 

One of the critical functions of water in the skin is to participate in hydrolytic enzymatic processes required for normal desquamation. 

In other words - water is necessary for the enzymes to function properly. 

If the skin water content falls below a critical level, the enzymatic function required for normal desquamation is impaired, leading to skin cells sticking and building up on the skin surface (Verdier-Sévrain et al, 2007). 

These changes lead to the visible appearance of dryness, roughness, scaling, and flaking (Verdier-Sévrain et al, 2007).

Learn more: What is Dehydrated Skin?

Skin Moisture Barrier - What Is It?

What are natural moisturizing factors (NMFs)?

The role of the natural moisturizing factors is to maintain adequate skin hydration.

The outer skin layer is called the stratum corneum and it is made up of cells called corneocytes, which form the physical barrier of the skin. 

Corneocytes are filled with keratin filaments as well as amino acids and other small molecules, collectively referred to as natural moisturizing factors (NMF), derived from the breakdown of filaggrin, a protein that surrounds the keratin filaments (Verdier-Sévrain et al, 2007).

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).

Skin Moisture Barrier - What Is It?

What is hyaluronic acid?

Hyaluronic acid is well known as one of the major components of the dermis, and is highly hygroscopic, meaning it can absorb moisture from the air.

Hyaluronic acid provides hydration and structural integrity to the dermis (Verdier-Sévrain et al, 2007).

What is glycerol?

Glycerol is also known as glycerin.

The beneficial effects of glycerol on the skin have been recognized for over 75 years, and glycerol has been widely used as an ingredient of skincare formulations for its moisturizing and smoothing effects (Fluhr et al, 2008). 

Interestingly, it has been shown that glycerol is made by our skin in the pilosebaceous unit and transported through aquaporin-3 (AQP3) channels to the skin. 

Endogenous glycerol plays a role in skin hydration, cutaneous elasticity and epidermal barrier repair (Fluhr et al, 2008).

Skin Moisture Barrier - What Is It?

Summary

The skin moisture barrier is a part of your skin barrier. 

The skin moisture barrier is composed of water, natural moisturizing factors (NMFs) and other humectants, such as glycerol and hyaluronic acid to attract and hold onto moisture.

The skin moisture barrier ensures your skin is hydrated by trapping and holding water into your skin.

Do you want healthy skin?

Sign up for Dry Skin Love Newsletter below

 What is Dry Skin? Sign up for newsletter below.

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. 

Warner RR, Myers MC, Taylor DA. Electron probe analysis of human skin: determination of the water concentration profile. J Invest Dermatol 1988; 90: 218–24.

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.

Fowler J. Understanding the Role of Natural Moisturizing Factor in Skin Hydration. Practical Dermatology. 2012; July. 36-40.

Rycroft RJ. Low humidity and microtrauma. Am J Ind Med 1985; 8:371–3.

Verdier-Sévrain S, Bonté F. Skin hydration: a review on its molecular mechanisms. J Cosmet Dermatol. 2007 Jun;6(2):75-82.

Milstone LM. Epidermal desquamation. J Dermatol Sci. 2004 Dec;36(3):131-40.

Fluhr JW, Darlenski R, Surber C. Glycerol and the skin: holistic approach to its origin and functions. Br J Dermatol. 2008.

← Older Post Newer Post →



Leave a comment