Adequate moisturisation is the cornerstone of skin health and beauty. John Woodruff gives his edit of ingredients to hydrate our skin and strengthen its integrity
A person’s face reveals personality, health and character, and it is that part of ourselves by which we are recognised. The face is covered in skin and the outermost layer of the skin’s epidermis is the stratum corneum (SC).
Healthy SC is a versatile material that combines the functional property of being an effective transport barrier and the material properties of being soft, strong and sufficiently pliable to tolerate deformation from physical strain and stress.
Keeping skin in good condition is part of the recognised function of cosmetics, and keeping it in good condition means keeping it properly moisturised, which is the focus of this feature.
The SC is approximately 10-15μm thick and comprises corneocytes embedded in a multi-lamellar lipid matrix in a fashion often described as a ‘bricks-and-mortar’ structure.
Water evaporates through skin to the external environment due to the water vapour pressure gradient on both sides of the skin barrier. It is referred to as transepidermal water loss (TEWL).
Increased TEWL impairs enzymatic functions required for normal desquamation, resulting in the visible appearance of dry, flaky skin.
The retention of water in the SC is dependent on the presence of natural hygroscopic agents within the corneocytes, collectively referred to as natural moisturising factor (NMF), and on the SC intercellular lipids being arranged in an orderly way to form a barrier to TEWL.
Cosmetic ingredients with claims to improve skin moisture levels are aimed principally at supporting the NMF and regulating TEWL by improving barrier function. In so doing they impart additional benefits.
Nouryon suggests that skin care products should reduce fine lines and facial wrinkles, improve elasticity and firmness of skin, and provide higher levels and longer lasting skin hydration.
It makes these claims for its Hydrovance Moisturizing Agent comprising hydroxyethyl urea in aqueous solution.
Nouryon undertook a series of in vivo trials comparing gels containing 5% Hydrovance versus gels containing 5% glycerin. Results showed that both gels improved short and long-term skin hydration and elasticity, and there was no significant difference between them.
However, an expert sensory panel compared absorbency, gloss, stickiness and the amount of residue at the immediate after feel of Hydrovance, glycerin, sodium PCA and urea in aqueous solution.
Hydrovance was rated significantly better than glycerin and better than or equal to the other moisturising agents tested.
The lipid layer separating the corneocytes of the SC is a mixture of ceramides, cholesterol and saturated long-chain free fatty acids in a lamellar gel-like structure that is essential for maintaining a tight water barrier and low TEWL.
Approximately 10% of the corneocyte mass is the NMF, comprising free amino acids, inorganic salts, sugars and lactic acid, with the balance being proteins.
Trimoist KMF from Mibelle Biochemistry is described as a three-step moisturising system that supports the skin’s own moisture balance system.
It contains CM-Glucan to enhance the skin’s defence system and build a superior protecting film. Skin-like lamellar lipids boost the barrier function of the lipid layer, and the humectants glycerin and sodium lactate provide an instant burst of hydration.
Trimoist KMF also contains carnosine, which prevents the crosslinking and stiffening of collagen and elastin by glycation, a process that leads to loss of skin elasticity.
Omega-CTP-Active PHE from GfN & Selco contains a mixture of amino acids, free radical scavengers and peptides, entirely of plant or synthetic origin (INCI: Aqua, glycerin, arginine, panthenol, proline, sorbitol, glycine, hydrolyzed soy protein, bis(tripeptide-1) copper acetate).
The di- and triglyceride content in olive oil has good affinity with human skin
Omega-CTP-Active PHE increases cell metabolism and is a potent antioxidant that protects the skin from free radicals. The amino acids L-arginine and L-proline are important for the water balance of tissue.
L-proline has the highest water binding capacity of all amino acids and L-arginine is metabolised to ornithine and urea in the skin, improving hydration of the SC and sustaining the epidermal barrier function.
Sabal Serrulata Lipophilic from GfN is a lipophilic extract from the fruits of the small palm Serenoa repens, rich in b-sitosterols and free fatty acids.
It is claimed to recover skin barrier function and fight inflammations of irritated skin. It reduces the production of inflammatory markers like IL-6 and helps to regenerate the integrity of the skin barrier after induced damage.
According to IFF-Lucas Meyer-owned Southern Cross Botanicals, because of their geographical isolation, plants of the Australian rainforest have developed unique survival mechanisms that enable them to thrive in a highly competitive tropical ecosystem.
The unique combination of powerful antioxidant fruits in its RainForest Harvest AF will nourish, moisturise and soothe skin, and fight the ageing process.
It comprises aqueous-glycerin extracts of the fruits of lilly pilly (Syzygium leishmania), lemon aspen (Acronychia acidula) and Davidsonia plum (Davidsonia pruriens), all of which contain high levels of anthocyanins, which are strong antioxidants. Lemon aspen, meanwhile, is also rich in essential elements.
Red fruits are known for their polyphenol content, but recent studies have shown that the highest concentration of diverse polyphenolic compounds are present in specific parts of silver fir branches.
From Abies Labs comes Belinal C, an extract of silver fir (INCI: Abies alba wood extract, maltodextrin) that contains 36 polyphenols of a molecular weight below 1,000 da, so the penetration of the dermis is significantly improved.
Tests demonstrate its anti-inflammatory and skin lightening properties, and a clinical study showed that it improved skin barrier and decreased TEWL by 20%, while increasing hydration by 26% after 12 weeks of treatment.
Borealine Hydra is a mix of four actives extracted from the bark of red maple, black spruce, yellow birch and jack pine, obtained through a circular economy process by Bio ForeXtra and claimed to offer long lasting protection and hydration to skin by its supplier, IFF-Lucas Meyer.
The extracts are rich in polyphenols, stilbenes, flavonoids, proanthocyanins, lignans and hydroxycinnamic acids, and are targeted at aquaporin-3 gene expression to provide a long lasting moisturising effect of up to eight hours after one application.
Its INCI listing is glycerin, Picea mariana bark extract, Acer rubrum bark extract, Betula alleghaniensis bark extract and Pinus banksiana bark extract.
Also from IFF-Lucas Meyer, Hydrosella is an organic extract of wild rosella selected for its high betaine content. It stimulates the cellular intake of organic osmolytes and restores skin barrier function by increasing lipid and tight junction proteins’ production.
It is claimed to provide rapid and continuous improvement of skin hydration, and reduces skin water loss for up to 72 hours after application.
Olive oil and its derivatives are popular in skin care. The di- and triglyceride content has good affinity with human skin and enhances penetration through the SC.
CeraFluid from Roelmi is a liquid mixture of olive glycerides and ceramide-3 that provides long-term hydration, as well as improving adhesion amongst corneocytes, thus regulating skin barrier for water retention and protecting it from external aggression.
It also improves skin elasticity and smoothness, and helps to restore the barrier.
Avenacare is an oat beta-glucan ingredient from Lantmännen Functional Foods, which is a co-operative of 25,000 farmers in Northern Europe. The product comes from the waste stream of oat processing in the food industry and has anti-inflammatory and skin soothing properties.
Twainmoist from Sollice Biotech is a combination of high and low molecular weight polyglutamic acid obtained by fermentation of soybeans. The low molecular weight molecules penetrate the dermis to activate hyaluronic production while the high molecular weight material forms a silky-smooth film on the SC, reducing TEWL.
Fision Hydrate Pro (INCI: Aqua, sodium PCA, panthenol, glycerin, sodium hyaluronate, L-proline, hydroxyproline) from TRI-K is a clear, colourless liquid combination of natural moisturising factors, amino acids and pro-vitamin B5 that provides a hydrating active claimed to support skin barrier function to deliver immediate and long-term moisturisation, resulting in healthier, protected skin.
Twainmoist from Sollice Biotech is a combination of high and low molecular weight polyglutamic acid obtained by fermenting soybeans
Hyaluronic acid is a naturally occurring polysaccharide in skin’s connective tissue. It binds up to 1,000 times its volume in water to help skin retain moisture and suppleness.
It is available from various suppliers as the acid or sodium salt, and it also appears in many of the mixtures described here. Some materials are claimed to stimulate the skin’s own mechanism to boost synthesis of the acid.
ET-VC is 3-O-ethyl ascorbic acid from Corum, said to boost synthesis by up to 182%. Aquaphyline from Silab is an extract of wild pansy that is said to favour the renewal of epidermal hyaluronic acid.
Glucohyami from Alban Muller is an extract of Cichorium intybus or chicory, claimed to be a biomimetic activator of hyaluronic acid synthesis.
Mibelle Biochemistry encapsulated inulin within lecithin-derived liposomes to create Polyfructol Plus. According to Mibelle, inulin draws water from the environment into the skin, helping to keep it hydrated. In addition, it forms a smooth and pleasant film that acts as a skin-conditioning agent, leaving the skin soft and smooth.
Inulin also has prebiotic properties and by balancing the skin’s microbiota it enhances the natural protective barrier and improves moisture retention.
Sea Moist Complex from Gelyma is based on a synergistic association of natural osmotically active ingredients: glycerin, seawater rich in essential minerals, and an extract of the red seaweed Kappaphycus alvarezii, which provides bioprotective oligosaccharides.
Gelyma claims that Sea Moist Complex reduces dehydration by improving the structural integrity of the stratum corneum and the epidermal biosynthetic functions of dry skin, providing the ideal level of moisture for up 24 hours.
Crodarom Green Caviar from Croda is an extract of Caulerpa lentillifera, a green alga mainly comprising xylane-derived polysaccharides, known for their hydrating and smoothing activity, and oligoelements that bring energising and revitalising properties.
In vivo trials showed a statistically significant increase in skin hydration compared with placebo still visible at 24 hours after one application.
It is suggested that because Caulerpa lentillifera is exposed to high salinity in ocean water, it develops internal osmotic molecules to protect itself against dehydration and osmotic stress.
The same mechanism is used in Crodarom Green Caviar to protect human skin from dehydration by providing osmotic xylane carbohydrates.
Regulating osmosis within the skin is also the function of Hydrasoft Moist SAP from The Innovation Company. Comprising natto gum, Betula alba juice and butylene glycol, it is water dispersible, increases emulsion stability and forms a film on the skin.
1. Mojumdar EH, Pham QD, Topgaard D, et al. 2017. Skin hydration: interplay between molecular dynamics, structure and water uptake in the stratum corneum. Sci Rep. 7(1):15,712
2. Verdier‐Sévrain S, Bonté F. 2007. Skin hydration: a review on its molecular mechanisms. Journal of Cosmetic Dermatology. 6:75-82.