Epidermal Dehydration: A Cause, not a Condition

Florence Barrett-Hill

Have you ever wondered why you didn’t know exactly what you were looking for when it came to the skin condition called dehydration? Or that when you were in doubt about what to treat the skin with, you chose the treatment modality with the label suitable for dehydrated skins, knowing it wouldnt really do any harm.

The term dehydration is one of the most misused words in our industry, and this article has been written to dispel some of the myths and common misconceptions about water in the skin.
Fully understanding the role that free water plays in the functions of the cells and systems of skin is the place to start.
 

epidermal dehydration
Oil & water work in synergy to produce correct hydration of the epidermis

If there is not enough water in the bodies system the term dehydration is used to describe the lack of water and the remedy is to drink more water and raise the hydration.
In the early to mid 1950s the first moisturisers came on the market, and skin care companies looked for a word that would describe a lack of water in skin. The word dehydration was the result and has been the terminology used by skin care companies to sell moisturisers ever since.

The word to moisturise is easily related to water, giving the illusion that there was a perceived lack of water in the skin (dehydration), a moisturiser would alleviate the problem. Suppliers and formulators of beauty therapy products pick up on the word dehydration and used it to describe salon treatments and products that were used to moisturise skin. 

Along the way the true understanding of the word dehydration got lost, and consequently we as professionals got lost as well.

Dehydration means a lack of free water within a system
Therefore diagnosis of dehydration is difficult because it isnt there to be seen as a specific skin condition. The lack of free water (dehydration) is however, a cause of a number of other skin conditions such as: Excess keratinisation, impaired lymphatic system and accelerated skin ageing conditions like collagens loss of structural integrity. 

It is important we remember that epidermal hydration is directly affected by the fluid intake of the client, and if that fluid intake is not maintained at an acceptable level, all secretion, respiration and transpiration functions of the skin will eventually become impaired.
It is the impairment of these functions and systems that manifest themselves as the various skin conditions that have historically been bundled together as dehydration. 

Today, we are wiser and understand that each of these conditions should be identified and treated as separate entities to obtain best results as each have different side effects on other complementary systems.
When we used to say, the skin is dehydrated, what where we referring to as the specific condition to be treated? What was the cause of this dehydration we were looking at? What specific systems were affected and what was the course of remedial action to be taken? Did we just advise our client to drink more water and the condition will clear up?
Let us explore how we can dispel the often misused and generalised term dehydration, and replace it with the correct terminology that better describes the water phases of the skin, its origins and systems cycle.

dehydration
TEWL is influenced by a number of factors

Balanced hydration is determined by four major factors:
1. The relevant ambient humidity
2. The retention power of the stratum corneum
3. The quantity of water transmitted from the inner to the outer layers
4. The time span the water takes to move from the lower skin layers to the stratum corneum. 

These four things all influence the movement of water through skin, and when talking about water movement we use the words Trans Epidermal Water Loss/Flow (TEWL). 

There is a simple law of physics that can be applied to TEWL and that is; Oil sits on top of water. 

Logically, if we wanted to retain water within the epidermis or to slow down water movement, the oil phases of the skin are the key to achieving this. To let ourselves fully understand these systems and subsystems, and the relative effects they have on skin health, we will have a quick review of the fluid balance systems of the skin.

 

dehydration
Balanced hydration is dependent on a number of factors

What is responsible for a well-hydrated skin?
Balanced hydration of skin begins with a well functioning lymphatic/circulatory system. Interstitial fluid is brought into the dermis via the circulatory system; here it will be attracted to the hyaluronic content of the glycosaminoglycans (GAGs) in the dermis that was made by the fibroblast.
A percentage of free water will move through to the epidermal basal layer, and become part of the water phase of the epidermis, this will be added to by amino acids that were made by the breakdown of fillagrin in the granular layer.

The water retention power of the epidermis
The retention of water in the epidermis for as long as possible will aid enzyme activity and cell health. The oil phases of the epidermis mentioned are part of the defence systems that slow down the movement of water through the epidermis and evaporation of epidermal NMF. (Water phase)

Lymphatic system
In order to maintain optimum protection characteristics, the hydration levels in the lymphatic/circulatory network must be balanced, with hydration levels out of balance exhibiting distinctive skin conditions such as excess keratinisation caused by impaired enzyme activity or collagens loss of structural integrity aggravated by low dermal reserves.
Epidermal & dermal hydration is directly affected by the fluid intake of the client. If the fluid intake is not maintained at an acceptable level, all secretion, respiration and transpiration functions of the skin will eventually become impaired.

Relevant ambient humidity
The relevant ambient humidity also plays a role in the hydration of a skin. Conditions of high humidity will result in lower transdermal water losses and more balanced hydration levels. Conversely, conditions of low humidity (dry air) will cause higher than normal transdermal water flows and consequently, lower hydration levels of the epidermis.

The Stratum Corneum
The corneocyte also plays a role in slowing down water movement through the skin because it is a hydrophobic cell (repels water), in addition the corneocyte assists in keeping antigens out of the viable epidermis and of course is the surface on which the acid mantle rests.

dehydration
The bilayers of the stratum corneum play a major role in slowing down TEWL

Maintaining the skin lipid levels
The acid mantle is the first line of skin barrier defence and plays an integral role in slowing down water movement within skin; as a result it also plays a role in maintaining a percentage of free water within the epidermis.

The Epidermic lipidsthat make up the bilayers of the stratum corneum are the third in line of skin barrier defence. 
These are made by the keratinocyte during its cycle through the layers of the epidermis
Ultimately ceramides make up to 40% of these epidermic lipids and plays a very big role in slowing down trans epidermal water flow through skin. 

This percentage of free water is vital for the large amount of enzyme activity that occurs in the granular layer of the epidermis. 

Enzyme activity
Water regulates almost every enzymatic and chemical reaction of the body; enzymes are the first of the workers in the body. They are the catalyst that allows the minerals and vitamins in your body to do their job and are responsible for all metabolic functions. Consequently if there is a lack of free water in skin there will be an impairment of the enzyme activity required for skin health. 

As an example the skin condition excess keratinisation is exacerbated by poor dissolution of the desmosomes that tether keratinocytes to one another. This dissolution is assisted by the enzymes protease and glycosidase and will not be efficient without a percentage of free water for the enzyme activity required.  If this dissolution of desmosomes does not occur the keratinocyte will not be fully prepared for desquamation and may build up on the skin surface or cause comedones by blocking the pilosebaceous duct.

Skin Secretions: the systems involved and the related skin conditions
Remembering to think of and to treat all the systems that are directly involved with retaining water within skin is the secret. These systems are as follows: 

• Acid Mantle
• Sebaceous Secretions
• NMF & TEWL
• Epidermic Lipids
• Lymphatic System

By the therapist building and maintaining all skin barrier defence systems and the client ensuring that adequate water is consumed to assist the internal hydration of the body, will result in the ultimate hydration of the dermis and epidermis. The skin should then be able to maintain the systems and cells that reside within it.

Impaired enzyme activity is the new dehydration
This article has been a brief overview of the importance that water in relationship to a well functioning skin and related systems.

Understanding that dehydration is old cosmetic terminology given to the movement of water through skin and is a cause of other skin conditions, not a cause in its own right will bring you into the new millennium as a modern skin treatment therapist.


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