What is Dehydrated Skin?

Posted by Dr. Natasha Ryz on

Blue Ocean Water. What is Dehydrated Skin? Dry Skin Love Luxury Skincare for Dry Skin by Dr. Natasha Ryz. Calgary, Alberta, Canada

What is Dehydrated Skin?

Dehydrated skin is skin that is lacking water and water-holding substances, called humectants.

Dehydrated skin appears dry, rough, and may scale and flake. It may also show premature signs of aging, like surface wrinkles and loss of elasticity.

Dehydrated skin can happen to anyone, regardless of skin type — if you have dry, oily or combination skin, you can still experience dehydration.

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). 

Water and Desquamation

Daily insults from the environment, such as low humidity, surfactants, wind, and sun, can lower the skin's water content, causing improper desquamation and the appearance of dry, flaky skin (Verdier-Sévrain et al, 2007).

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).

Natural Moisturizing Factors (NMFs)

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

Our 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).

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).

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).

Summary

Dehydrated skin is skin that is lacking water and water-holding substances, called humectants.

Humectants include natural moisturizing factors, hyaluronic acid and glycerol.
To summarize, dehydrated skin:
  • Skin appears dull, loss of elasticity and fine lines are more pronounced.

  • Dehydrated skin is a condition that anyone can experience.

  • Caused by a lack of moisture in the stratum corneum, which is the top layer of the skin

 

References

Dehydrated Skin Dry Skin Skin Science Skin Type Skincare Water

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