When we say the word dehydration we most likely think of being thirsty during exercise. Perhaps our skin feels parched or dry after being in the hot sun. Do you live in a climate that is seasonal such as in regions that use heat in the cooler months or air conditioning in summers? Depending upon where you reside, the relative humidity within your environment greatly influences the balance of skin moisture. These variations may affect how the skin feels as well as interfere with its ability to have good moisture balance. Transepidermal water loss (TEWL) is the quantity of water that passes from inside the skin to the surrounding atmosphere. Damage to the skin through injury, infection, burns and other assaults will impair the functioning of the epidermis and its ability to retain a good water balance.
Dehydration may be a temporary condition within the body or it can be a deeper issue concerning lack of free water within the epidermis causing transepidermal water loss (TEWL).2 Discovering the underlying cause of this condition is essential for making appropriate choices to manage or correct dry skin conditions. There may be several explanations2 why the skin appears dry.
- Intrinsic (genetic traits) or extrinsic (life style) or acquired disease.
- Extrinsic factors: Sweating: the body maintains temperature through perspiration. Playing sports, running, and staying too long in the sun may indeed cause a temporary water loss. The skin barrier is still very balanced but you experience feeling dry due to these extrinsic factors.
- Intrinsic Factors: (a) Poor skin barrier: You may have a barrier disorder with enzymatic impairment within the bi-layers affecting water disbursement throughout the granulosum and stratum corneum layers. (b) One’s ability to maintain water balance decreases with age or through illness.
- The acid mantle has been disturbed through poor care, illness, or over-processed skin, i.e., excessive peels, microdermabrasion, and continuous use of abrasive products that disturbs the epidermal bi layers.
- Deep wounding or injury disturbs the acid mantle and moisture barrier.
It is not enough to say that the skin is “dehydrated” and base a remedy strictly on this observation. Instead we should explore several parameters from a newer paradigm that provides skin indicators based on “texture”, “secretions” and “colour”. Within each indicator are parameters relating to skin conditions and understanding their effect on cells and systems. A good diagnostic tool, a skin scanner, and the client’s health profile all provide vital information that uncovers possible risk factors and the probability of outcome regarding a treatment programme.
Water movement within the skin
The systems that are directly involved with skin secretions are2:
- Acid mantle
- Epidermal lipids
- NMF (natural moisturizing factors) and TEWL (transepidermal water loss)
- Sebaceous Secretions
- Lymphatic system
Since we are speaking about dehydration, this article will focus on the structures within the epidermis that are responsible for moisture retention and balance. All tissue must maintain sufficient water balance for proper function including the ability to adjust within one’s environment.7 Balanced hydration is based on the following facts.2
- Relevant ambient humidity.
- The retention power of the stratum corneum.
- The amount of water transmitted from the inner to the outer layers of the skin.
- The time span involving how long water moves from the lower skin layers to the upper regions of the stratum corneum.
Relevant ambient humidity
Skin hydration depends on a functioning natural moisture factor, the skin barrier, and balanced sebum. The skin continuously adjusts between outside atmospheric conditions and the temperatures maintained inside our homes and place of work. Depending upon where you live – arid regions such as high dessert, mountainous or tropical regions – the skin transitions with the atmospheric changes in order to maintain its natural moisture levels. Extreme changes of relative humidity may begin to stress the skin. It begins to have difficulty maintaining internal moisture levels. Air conditioning and heating systems change indoor atmospheric humidity. These transitions can easily become skin stressors as it (skin) continuously adjusts between inside and outside atmospheric conditions. In dry conditions, TEWL is much greater. It stands to reason that facial moisturisers may not be as efficient when there is very low humidity since there is a characteristic threshold for every moisturiser.7 It becomes inefficient and releases the moisture in the surrounding air.
Humidity can be measured in several ways. The most common is relative humidity and to understand this even further the physics of absolute humidity states that the hotter the air is, the more water it can contain. In other words, when there is 100% relative humidity, the air is totally saturated with water vapour and cannot hold any more.9 When the humidity is high, we actually feel hotter than the actual temperature because sweat will not evaporate. The higher the humidity, the more uncomfortable we are due to the fact that our body cannot cool. Conversely, when humidity is lower, we feel cooler because our body is able to maintain its appropriate temperature. Incidentally, clouds are condensed water vapour high in the sky as a result of warm air rising from the earth. They form to equalize the temperatures in the air.
The atmospheric humidity approximately halves with every 10o C. When air with a relative humidity of 100% at a temperature of 0o C is warmed to 10o C, atmospheric humidity becomes about 50%. Warmed to 20oC, the humidity moves to around 25%. Comfort levels for humans are about 45% humidity.
Skin moisturisers and humidity
TEWL increases when the air becomes dryer. Balancing the skin barrier during changing environmental conditions becomes challenging. Moisturisers play a significant role by increasing skin elasticity as well as smooth the skin. They also become very inefficient in arid climates. Instead of releasing moisture into the skin, it evaporates into the dry circumambient air.4 Even when we re-apply, it isn’t enough. Well penetrating moisturisers that contain ingredients such as urea, glycerin, and glycols just cannot compensate due to their low molecular weight.4 An ideal moisturiser for dryer climates is to use hyaluronic acid, CM-Glucan, and other agents that form an additional barrier to prevent TEWL on the skin surface. When humidity gets even lower with higher temperatures, the quantity of lipid substances including phytosterols in skin care should be increased. Precaution should be taken when recommending for cases of rosacea skin conditions. Reapplication with too much moisture on this type of skin may lead to irritations including increasing the risk of creating an environment that encourages the growth of anaerobic bacteria that further perpetuates skin irritation.
Retention power of the stratum corneum
The process of differentiation and keratinization within the epidermis is a strategic process whose purpose is to build a strong barrier defense system for the skin. As the keratinocytes migrate upward from the spinosum layer into the granular layers, their cellular contents begin to transform into hardened filaments (keratohyalin structures) making the cells less flexible. The granular layer is very important for synthesising material for the stratum corneum. Cells at this layer produce membrane-coating lamellar granules called Odlund bodies that contain lipids and proteins. The lipid mixtures in the lamellar granules are made up of ceramides, cholesterol, free fatty acids and cholesterol sulfate. They are dedicated lipid-rich apparatuses that extrude their lipidic and enzymatic contents through the keratinocyte cell membrane out into the extracellular spaces where they come in contact with the water (NMF – natural moisturizing factors). The lipids then form two layers, one of oil and the other of water and are reorganized into multiple long sheets of lamellar structures. These structures play a dynamic role in barrier defense and controlling transepidermal water flow and maintaining proper hydration levels within the epidermis.
The epidermal tissue must remain as impermeable as possible with the exception of allowing enough water to maintain hydration at the outer layers of the stratum corneum as well as supporting the enzymatic processes that facilitate corneo-desmosomal degradation and desquamation. The water content supports skin flexibility and the ability to adjust to relative humidity (internal and external). The ability for the stratum corneum to maintain its water content is dependent upon (a) the thickness of the stratum corneum and (b) the organisational and compacting characteristics of the corneocytes that allow them to function properly and (c) the presence of very hygroscopic (NMF) compounds largely found within the corneocytes.
NMF – Multi-function Qualities
The natural moisturizing factors (NMF) are composed primarily of amino acids, PCA and other compounds. The hygroscopic properties of NMF greatly contribute to the corneocytes’ ability retain moisture. NMF also facilitates enzymatic processes including the dissolution of the desmosomes. NMF consist of amino acids that are not only responsible for the moisture content of the skin but also for the osmolytic balance, i.e., they correct imbalances in the osmotic pressure of the skin. Furthermore, the amino acids and the urea of the NMF protect against ROS (reactive oxygen species – free radicals).
The skin has a network of enzymatic and non-enzymatic antioxidant systems that help combat oxidative injury from pollution, bacteria, UVR (ultraviolet rays), microorganisms, or chemical oxidants. The normal functioning of these systems is reliant upon a balance of lipid and protein systems that maintain the barrier function and are essential for skin moisturisation. When there is oxidative stress within the lipid and protein structures of the cells it degrades the barrier integrity. The skin begins to show signs of dryness with the increased water loss (TEWL).
Caring for the skin barrier
The stratum corneum contains signal functions that influence important controls within the epidermal layers. The horny layer has a direct influence of the regenerating process in the deeper layers of the skin. The normal function of the skin barrier declines with age including lipid synthesis and the pH of the acid mantle. Choosing correct products for protecting the barrier is based on several factors, especially the age of the client, life style, and the extent of accumulated damage. Many cosmetic products actually can interfere with the natural TEWL process. Mineral oils and silicones form too much of an impermeable film on the skin. They can easily cause a lower transepidermal water loss that actually slows down the regeneration process. The client ends up experiencing dry skin upon discontinued use of these substances. The perplexity of this situation is compounded since there wasn’t a clear understanding that the skin barrier began to experience disorder and lost its ability to regenerate with the use of inappropriate cosmetic or dermatological products. Moreover the prescribing of corticosteroids for inflammations provide a temporary relief, however, they actually contribute to increased skin sensitivity and deterioration of the condition.
Transitioning into products based on corneotherapy
When introducing skin care products based on corneotherapy principles, one must allow sufficient time for the skin to return to its normal and natural metabolic activity.6 The chemical and physical properties of a product greatly influence the integrity, regeneration and preservation of the horny layer. A key philosophy is to preserve the natural function of the epidermal layers. Choice of products should mimic the physical structures of the skin, be free of emulsifiers and contain the appropriate active agents such as linoleic acid to support the skin in reactivating its own regeneration capability. The skin is gently influenced with products that support its own environment in order to return to a more balanced state.
We now understand that true dehydration is really a condition that has to do with an impaired barrier function. It is important that we consume enough water on a daily basis and eat a variety of fresh fruits and vegetables along with quality protein and foods that are high in essential fatty acids. Life style habits including sufficient and undisturbed rest, and exercise all contribute to optimal health.
Based on corneotherapy principles, dermavidual® products with DMS® resemble the membrane structure of the natural skin barrier. They are both preventative and supportive to an existing problem. Recommended solutions for dry skin: DMS® High Classic Plus/liposome NMF concentrate, süüsmoon Lotion N, Rosehip Oil, as well as Hyaluronic Acid and Liposomes Plus. Each system should be customised for each client based on his or her personal skin condition. Barrier disorders also benefit from:
- Phytosterols – shea butter, avocado (skin protection)
- Fumaric acid – liposomal (psoriasis) (Lotion P)
- Aloe vera Extract – dry and cracked skin)
- Hammamelis Extract (dry and cracked skin)
- Evening Primrose Nanoparticles (atopic skin, dry skin)
- Linseed Oil Nanoparticles (atopic skin, dry skin)
- Akemi IshidaYamamoto, M. Simon, M. Kishibe, et al. (2004) Epidermal Lamellar Granules Transport Different Cargoes as Distinct Aggregates. J Inv Derma 122, 1137-1144; Retrieved from http://www.nature.com/jid/journal/v122/n5/full/5602318a.html
- Barrett-Hill, F. (2005). Advanced Skin Analysis. Virtual Beauty, New Zealand. p. 102
- Elias, P.T., Feingold, K.R. (2009) Skin Barrier. (23) Taylor & Francis, New York. p. 399, 407
- Lautenschläger, H. (2011) Moisturizers in skin care. Beauty Forum (3), 86-88 and 2011 (4), 46-49.
- Lautenschläger, H. (2007) Applied corneotherapy and skin care: guidelines for the anti-aging treatment. Ästhetische Dermatologie (3), 8-16
- Lautenschläger, H. (2000) Regeneration of the skin barrier. Kosmetik International (8), 100-103
- Rawlings, A.V. (2006). Skin Barrier: Chapter 24, Sources and Role of Stratum Corneum Hydration, Chapter 24. Taylor & Francis Group, NY, London.
- Svane-Knudsen, V., Halkier-Sorensen, L., et al. (2000) Stratum corneum barrier lipids in cholesteatoma. Acta Otolaryngol Suppl. 2000; 543: 139-42. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/10909003
- What is relative humidity and how does it affect how I feel outside? Retrieved from http://science.howstuffworks.com/dictionary/meteorological-terms/question651.htm
This dossier has been prepared on behalf of dermaviduals Australia and New Zealand as a reference that relates to various skin conditions. In no way does it replace the advice of your medical practitioner or a dermatologist. All views represent the research and findings of the writer in conjunction with derma aesthetics.