Skin Hydration

By Lorna Bowes / 26 Jun 2017

Aesthetic nurse prescriber Lorna Bowes details the role of hydration in healthy skin

From looking through the myriad of consumer marketing, it appears to be easy to get airbrushed, glowing, well-hydrated skin; you apply vast amounts of high street moisturisers and that does the trick. 

We’re also told that by drinking eight glasses or two litres of water a day this will give us the hydrated, youthful skin we are looking for and even flush out toxins. But what actually delivers the dewy look so sought after by our patients?

Dr Katie Rodan, board certified dermatologist from the US, is credited with providing the simple explanation that, “Human’s are not like plants. Our skin doesn’t perk up when we consume water, water goes through the intestines, gets absorbed into your bloodstream, and is filtered by kidneys. Then it hydrates cells.”1 This view is shared by nutrition scientist Heather Yüregir, “Just drinking water for the sake of drinking water really has no effect on improving the appearance of skin. It is just a common misconception.”2

Water balance in the skin

Hydrobalance – the water balance in our skin – is a balance between adequate supply and generation of water and prevention or reduction of trans epidermal water loss (TEWL) in the stratum corneum (SC), which is the outer layer of the skin, moderated by both lipids and natural moisturising factor (NMF).3 The stratum corneum comprises mature keratinocytes and, on average, is 15 cell layers thick.4 The structure of the stratum corneum can be described as similar to ‘bricks and mortar’; the ‘bricks’ are the keratinocytes, and the lipids and amino acids are the ‘mortar’.4 Amino acids, as well as other osmolytes in the stratum corneum such as glycerol, lactic acid, taurine and urea, act as a humectant, a substance used to reduce loss of moisture.5 

NMF is only found in the cells of the stratum corneum, and is highly humectant, being composed of water-binding chemicals.6 Being able to maintain a good level of hydration, even in a dry environment and in conditions such as ichthyosis vulgaris, where patients have reduced levels of NMF, is important for the various enzymes that have activity in the stratum corneum and rely on a moist environment to function.7

Water loss

It is important that the water content of the SC is at least 10% for our skin to feel and look ‘correctly hydrated’; when skin becomes dry, cracks and fissures appear.8 Most people with dry skin do not have an underlying disease, but are exposed to factors such as hot water, detergents, pollution, air travel, air conditioning, and even friction from clothing, as well as the dryness associated with autumn and winter months when humidity may be lower and patients are more likely to take hot baths.6

Topical application of emollients may improve skin barrier function and improve the appearance and feel of dry skin

It is important to note that TEWL is not the same as perspiration. TEWL is better described as insensible water loss through the skin, and is now used as an indicator of the integrity of the SC.9 Perspiration is carried out by eccrine sweat glands, distributed evenly over most of the body.10 Severe dehydration can affect the skin, causing tenting, and skin turgor;11 in these instances increased water consumption can improve skin thickness and density, however in healthy and adequately hydrated patients, increasing water consumption will not reduce fine lines and wrinkles, nor will it prevent other signs of ageing associated with genetics, or damage from UV and the environment.12,13 However, topical application of emollients may improve skin barrier function and improve the appearance and feel of dry skin.14

Lipids also make up around 10% of the SC by weight, and play a critical role in maintaining the watertight barrier that is in the skin.15 Dry, dehydrated skin leads to abnormal desquamation of corneocytes16 shedding of the outer layer of the skin, leading to clumps of corneocytes that leave skin looking uneven and dry, which appears as ashen coloured in darker skin.17

Components in the skin

In total, the skin contains approximately 30% water, and this quantity of water is visible through the plumpness, elasticity and resilience of skin. Lower layers of the skin, including the layers of the SC, are hydrated by body fluids rather than the humectant properties of the SC.5 The main cells of the dermis are fibroblasts, and the fibres of the dermis are collagen fibres and elastin fibres; with collagen fibres making up 70-80% of the dry weight of the dermis. Key dermal collagens are collagen type I (85% of skin collagen), collagen type III (15% of skin collagen) and small amounts of collagen types IV and VII. Elastin fibres only make up around 2% of dry dermal weight. Both collagen and elastin rely heavily on dermal water content being adequate. 

The ground substance of the dermis is made up of glycosaminoglycans, hyaluronic acid and dermatan sulphate, with smaller quantities of heparin sulphate and chondroitin sulphate.18 Glycosaminoglycans and ground substance provide various key functions; binding water, providing transport of nutrients, hormones, and waste products, lubricating the various dermal components such as collagen and elastin during skin movement and providing bulk and cushioning or shock absorbency.18

So, what actions can we take, or encourage our patients to take to increase hydration levels in the skin? 

Treatment options

Topical treatments

Moisturisers

The aim of moisturisers is to increase moisture levels in the skin, but this can be achieved in various different ways – reduction in evaporation and sweating, increased non-negative matrix factorisation (NMF), increased gylcosaminoglycans and improved skin barrier function. Moisturisers come in different carrier or vehicle formulations such as:19

  • Ointment (approx. 80% oil, 20% water)
  • Cream (approx. 50:50 oil: water)
  • Lotion (approx. 70% water 30% oil)
  • Serum (water-based)
  • Gel (water-based emulsion)

The vehicle used is often also one of the moisturising ingredients. For cosmetic preparations, creams, lotions and gels are commonly used, while moisturisers and serums tend to be carriers for active ingredients including antioxidants.20

Humectants

Humectants are the sponges of the skin – drawing water from the environment and atmosphere or from the dermis and underlying tissues. They are fundamentally short-lasting hydrators, but many humectants also deliver other properties that can claim to be antiageing or anti-wrinkle in addition to the transient hydration they offer. Glycerin (glycerol), urea, hyaluronic acid and its salt (sodium hylaronate), sorbitol, propylene glycol and hydroxy acids are all humectants. 

The hydroxy acid group of humectants is particularly interesting, as they also have widely reported antiageing properties. Gluconolactone, a polyhydroxy acid, is made up of multiple hydroxyl groups, as opposed to a single hydroxyl group like first generation AHAs (e.g. glycolic acid); the multiple hydroxyl groups attract water, providing enhanced moisturisation.21

Lactobionic acid, a bionic polyhydroxy acid from milk sugar, is a potent antioxidant which also has powerful humectant properties, strongly attracting and binding water. It is suitable for all skin types22,23 and its unique hydra-film delivers moisture, softness and smoothness to the skin.24 

Maltobionic acid has similar moisturising and hydration properties, and these advanced third generation hydroxy acids, lactobionic and maltobionic acid, are also powerful antioxidants trapping oxidation and promoting metals. They also prevent oxidative damage to lipids as well as inhibiting matrix metalloproteinases (MMPs) to preserve the dermal matrix increasing glycosaminoglycans and plumping and firming the skin, delivering anti-glycation effects, and demonstrating significant antiageing effects.23,24,25

Emollients

Emollients such as cetyl stearate, glyceryl stearate, octyl octanoate, decyl oleate and isostearyl alcohol, are used to soften and smooth the skin, and can fill in the gaps between the corneocytes, creating a smoother appearance. They may also be occlusive oils that offer an airtight barrier against water loss from the skin, thereby increasing hydration.26

Injectables

Mesostherapy

Various dermal filler ingredients have been demonstrated as effective biostimulants, increasing hydration and fibroblast activity. The technique known as meostherapy has been used around the world since it was coined in the 1950s by Dr Michael Pistor.27 Ingredient choice has been based on those that can improve fibroblast function and activity and improve biosynthesis of the extracellular matrix, increasing hydration.28

Organic silicium (SI(OH)4) is essential for wound healing,29 and has been used in mesotherapy solutions for many years, particularly for its benefits in increasing collagen production.30 Various studies have demonstrated the effects of organic silicium,31 one demonstrating a 2,400% increase in hyaluronan synthase 2 (HAS2) gene expression; HAS2 is responsible for the majority of high molecular weight HA synthesis in humans.32

Higher levels of Si are reported to be associated with healthy connective tissues (such as aorta, bone, trachea, tendon) and especially their connective tissue components, collagen and elastin...

Silicium (Si) is a natural trace element present in the mammalian diet and is important for the normal health of bone and the connective tissues.33,34,35 Indeed, dietary Si deprivation in growing animals appears to cause abnormal growth and defects of the connective tissues. Moreover in connective tissue, silicium is present as organic silicium Si(OH)4.36,37 However, much of the evidence points to a direct involvement of Si in extracellular matrix synthesis and/or its stabilsation, particularly so for collagen, which is one of the main structural proteins of bone and connective tissues.35,38 

Higher levels of Si are reported to be associated with healthy connective tissues (such as aorta, bone, trachea, tendon) and especially their connective tissue components, collagen and elastin, compared to non-connective tissues including liver, kidney and spleen.39,40 There is a 4-5 fold difference in (Si) between connective versus non-connective tissues (adult rats). Serum Si levels is a serum marker of type I collagen turnover.41 Si/collagen molar ratio is 1:6 in bones of rats, independent of age. This supports a structural role for Si(OH)4 as a cross-link between collagen units by the way of hydrogen bonds.42

In addition, it was recently demonstrated that organic silicium present in some injectable products could lead to a 25 fold hyaluronan synthase 2 gene expression, a 4 fold collagen type 1 and a 2.5 fold elastin gene expression when added in vitro to human skin fibroblasts, explaining why it can be so effective for skin rejuvenation purposes.43

Hyaluronic acid

HA has been in use now for well over 20 years, since the launch of Hylaform, a cockerel comb derived HA,44 followed by the many HA fillers that are available. This popularity has led to further research into the biostimulatory effects HA can have, as well as research into using the HA as a carrier medium for a variety of clinically-proven ingredients that also exhibit specific biostimulatory effects. In 2014 Baspeyras published a paper on the efficacy of a non-reticulated HA-based mesotherapy cocktail on radiance and elasticity. The study objectively demonstrated the efficacy and the tolerance of a non-cross-linked HA filler in sustainably improving skin elastic parameters and complexion radiance.45

A recent study in Clinical, Cosmetic and Investigational Dermatology presented experiments by Deglesne with Eurofins BioPharma Product Testing Spain SLU, an external independent certified laboratory, who reviewed the effects of HA on human fibroblast viability, collagen type I and elastin gene expression.46 This study used a resorbable medical device, long-chain non-cross linked HA at 6.66mg/ml for dermal biorevitalisation that includes a combination of other ingredients, including vitamins to support specific biologic reactions and cellular respiration, fatty acids to support the epidermal barrier function, coenzymes, antioxidants, polyphenols, amino acids and trace elements for cell nutrition. 

The authors reviewed the effect of the HA product on collagen type 1 and elastin genes that demonstrated increases in the expression of messenger RNA for collagen type 1 and elastin as early as 24 hours with maximal expression at 48 hours. In this in vitro study, the authors found that the HA injectable could promote a nearly tenfold increase in type 1 collagen gene expression and a 14-fold increase in elastin gene expression, demonstrating that the biorevitalisation product used can, at least in vitro, modulate human skin fibroblasts and produce glycosaminoglycans increasing the hydration of the skin.46

Conclusion

In conclusion, adequate hydration of all layers of the dermis can aid a patient in reaching their antiageing goals, and by targeting the SC, epidermis and dermal components with ingredients, whether applied topically or using mesotherapy and injection techniques, there is a body of evidence supporting certain key ingredients. 

References

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