Before the invention of moisturiser, serums, and oils, skin relied solely on self-created natural moisturising factor. A combination of ingredients able to soothe, soften and hydrate in tandem. Today, with the invention of air conditioning and central heating, through the discovery of soaps and surfactants, because of the industrial revolution and its consequential effect on pollution levels – skin needs a helping hand.
Your skin is best cared for when a ‘helping-hand’ is lent through skin-identical ingredients. Ingredients which mimic skin’s natural moisturising factor. Ingredients skin knows how to use. Ingredients recognised as ‘one-of-our-own’.
What is natural moisturising factor?
Skins natural moisturising factor is comprised of many individual ingredients – most of which can be classified as humectants. Ingredients which act like magnets to water, binding and retaining hydration within the skin.
The absence or impairment of skins natural moisturising factors (NMF) is responsible for dry skin, xerosis, and eczema. Lack of NMF is also linked to ichthyosis, irritant-induced dermatitis, and skin sensitivity. When skin’s natural moisturising factors are depleted, skin conditions caused as a consequence of dryness arise.
What is the function of skin’s natural moisturising factor?
An adequately cared for natural moisturising factor performs 3 key functions towards the maintenance of a healthy skin type;
- Effective lubrication – increased plasticity of skin
- Facilitates desquamation (exfoliation)1
- Aids in the maintenance of barrier function
Skin having good plasticity feels comfortable, moisturised and maintains a high resilience. However, a skin type lacking in plasticity caused by a degradation of the natural moisturising factor becomes prone to cracking, flaking and wrinkle formation.
How does skin’s NMF cause increased skin plasticity? Components of skins natural moisturising factor absorb and attract water molecules, these water molecules in turn hydrate and dissolve components of skin’s NMF2. Hydrated molecules of NMF are able to interact with skin’s keratin fibres, therefore reducing the interactions from one keratin fibre to another3. This interruption allows keratin fibres to smoothly slide past one another, resulting in a comfortably, supple skin barrier.
Desquamation describes the natural process of skins ability to self-exfoliate. A cycle averaging a months’ time from cell birth to natural maturation and finally removal. When skin is able to effectively desquamate it appears moisturised, youthful and smooth. When skins desquamation processes are interrupted by a change to skin’s NMF levels, skin becomes patchy, flaky and roughened.
How does skin’s NMF provoke effective desquamation? When skin cells reach their final destination – the stratum corneum, they are technically described as dead. At this stage skin cells have differentiated from keratinocytes to corneocytes helping form an impenetrable skin barrier to defend skin against irritation, sensitisation, and infection. Although stratum corneum corneocytes are technically dead, many biochemical reactions are staged in the areas surrounding them. These intercellular spaces play home to enzymes whose primary purpose is to break the adhesion holding corneocyte skin cells together. These desquamatory enzymes require adequate hydration for activity. As levels fall, their ability to work follows4.
Healthy skin types have a barrier function able to retain hydration while also defending against bacterial attack. Skin that has a healthy barrier function is resilient, hydrated and soothed. Skin that has a reduced barrier function is sensitive, roughened and dehydrated. Skin types with reduced barrier function are commonly prone to contact dermatitis, infection, and allergy.
How does skin’s NMF contribute to effective skin barrier function? Skin is a complex organism having its own inherent metabolism. Every minute, hour and day that passes sees many biochemical reactions undertaken – each requiring adequate hydration. A factor supplied and guaranteed by skin’s natural moisturising factor. Studies show skin types with reduced or non-existent NMF are prone to the development of dry skin conditions such as psoriasis, dermatitis and ichthyosis vulgaris5,6.
What happens when skin is deficient in NMF?
Skin can become deficient in its natural moisturising factors because of both external and internal causes. The most well-known external causes resulting in a reduction of NMF are;
Exposure to sunlight
Use of cleansing agents (specifically cleansing products with high alkalinity)
These NMF declining factors can be corrected and compensated for via changes we will discuss in depth very soon.
In contrast, sometimes a reduction in skin’s NMF can be as a consequence of a person’s DNA. Mutations in the filaggrin protein are known to cause a reduction or complete lack of NMF. The filaggrin protein is active in helping to align keratin fibres correctly within the skin, however, once this function is performed the filaggrin proteins accompanies skin cells throughout maturation towards the top layers of skin. Within these layers, when conditions are right, filaggrin proteins are broken down into a mixture of components recognised as skins natural moisturising factor7.
So called, ‘loss-of-function’ mutations can be inherited through family lines. These changes noticeable in the filaggrin gene contribute to ichthyosis vulgaris8, early onset atopic eczema9 and predisposition to the development of atopic dermatitis10.
What ingredients are found in skins natural moisturising factor?
The ingredients present in skins natural moisturising factor, aid in hydration, plasticity and barrier function of the stratum corneum. When these ingredients are present in optimal concentrations, skin is able to perform all of its functions efficiently. When these ingredients are lacking or low in concentration, deficiencies in hydration, plasticity and barrier function arise as recognisable dry skin conditions e.g. eczema. Therefore understanding how to replenish skin’s NMF can help in the treatment and reversal of these conditions.
Skins natural moisturising factor is comprised of 8 grouped types of ingredients11;
- Free amino acids (40%)
- Ions – chloride, sodium, calcium (18.5%)
- Pyrrolidone carboxylic acid (PCA, 12%)
- Lactates (12%)
- Sugars, inorganic acids, peptides (8.5%)
- Urea (7%)
- Ammonia, uric acid, glucosamines, creatinine (1.5%)
- Citrate (0.5%)
Of all ingredients found within skin’s natural moisturising factor, Pyrrolidone carboxylic acid (PCA) contributes the highest individual percentage. When Pyrrolidone carboxylic acid is present in its free form it contributes poorly to hydration, however, when Pyrrolidone carboxylic acid is associated as a sodium salt (sodium being a key component of skin’s NMF ion fraction) its water attraction is greater than the commonly used humectant – glycerine. Studies show the daily application of creams containing as little as 2% may treat and relieve the symptoms of dry skin12.
Contributing the highest overall percentage of skin’s NMF, free amino acids play an important role in skin’s hydration and metabolic health. As skin ages, its amino acid content also declines – both changes closely correlate with a decrease in hydration level13. Amino acids can function as humectants and antioxidants while also helping to increase the plasticity of skin. Natural and basic amino acids are particularly good at forming the ionic interactions responsible for NMF’s ability to improve the movement of keratin fibres and therefore suppleness of skin14.
Lactates are a type of alpha-hydroxy-acid known for their ability to hydrate skin as a humectant. Lactates such as lactic acid are also able to aid and trigger desquamation. Their presence is strongly correlated to the increased synthesis of stratum corneum ceramides15 – oil based ingredients providing effective barrier function. Topical application of lactic acid based creams has been shown to treat and prevent the symptoms of dry skin16.
How can skincare help to protect and replenish skin’s natural moisturising factor?
Two of the most effective ways to alleviate a skin concern is to supply skin with the ingredients it’s lacking and to protect the ingredients it already possesses. In the case of skin affected by dryness, sensitivity, irritation and eczematous symptoms – replenishing and protecting ingredients found in skin’s NMF has beneficial results. There are 3 primary changes you can implement into your skin routine to achieve this;
- Use of skin-identical ingredients
Skin identical ingredients present a class of ingredient skin already knows how to use. They can be ingredients with an inherent benefit of their own, or ingredients skin knows how to turn into other skin beneficial ingredients – for example, the use of lactic acid in ceramide synthesis. Creams containing NMF identical ingredients such as urea17 and lactic acid have been shown to help alleviate dry skin symptoms.
- Avoidance of over-washing
Skins NMF is easily corroded by harsh cleansers. Many cleansers and soaps contain very strong detergents able to remove make-up and impurities alongside skin’s own natural moisturising factor18. Keep baths to a minimum, turn the temperature down when showering and use gentle gel cleansers such as the griffin+row Cleanse.
- Daily application of sunscreen
Although some of the factors causing dry skin conditions are hereditary, others are environmental and controllable. There are 2 environmental factors having a significant effect on the decline of skin’s NMF – bathing and UV exposure. To protect your skin’s inherent NMF, avoid direct exposure to sunlight between the hours of 10-2pm and apply a suitable sunscreen daily.
How does your skincare routine stack-up? Are you taking the necessary steps to protect and replenish your skin’s natural moisturising factor? Are you using skin-friendly cleansing products?
- Dry skin, moisturization and corneodesmolysis. C. R. Harding, A. Watkinson, A. V. Rawlings, I. R. Scott Int J Cosmet Sci. 2000 Feb; 22(1): 21–52. doi: 10.1046/j.1467-2494.2000.00001.x
- Stratum corneum moisturization at the molecular level. A. V. Rawlings, I. R. Scott, C. R. Harding, P. A. Bowser J Invest Dermatol. 1994 Nov; 103(5): 731–741.
- Molecular analysis of elastic properties of the stratum corneum by solid-state 13C-nuclear magnetic resonance spectroscopy. Y. Jokura, S. Ishikawa, H. Tokuda, G. Imokawa J Invest Dermatol. 1995 May; 104(5): 806–812.
- Dry skin, moisturization and corneodesmolysis. C. R. Harding, A. Watkinson, A. V. Rawlings, I. R. Scott. Int J Cosmet Sci. 2000 Feb; 22(1): 21–52. doi: 10.1046/j.1467-2494.2000.00001.x
- Marstein S, Jellum E, Eldjarn L. The concentration of pyroglutamic acid (2-pyrrolidone-5-carboxylic acid) in normal and psoriatic epidermis, determined on a microgram scale by gas chromatography. Clin Chim Acta. 1973; 49(3):389-95.
- Horii I, Nakayama Y, Obata M, et al. Stratum corneum hydration and amino acid content in xerotic skin. Br J Dermatol. 1989; 121(5):587-92.
- Scott IR, Harding CR, Barrett JG. Histidine-rich protein of the keratohyalin granules. Source of the free amino acids, urocanic acid, and pyrrolidone carboxylic acid in the stratum corneum. Biochim Biophys Acta. 1982; 719(1):110-7.
- Smith FJ, Irvine AD, Terron-Kwiatkowski A, et al. Loss-of-function mutations in the gene encoding filaggrin cause ichthyosis vulgaris. Nat Genet. 2006; 38(3):337-42.
- Brown SJ, Sandilands A, Zhao Y, et al. Prevalent and low-frequency null mutations in the filaggrin gene are associated with early-onset and persistent atopic eczema. J Invest Dermatol. 2008; 128(6):1591-4.
- Palmer CN, Irvine AD, Terron-Kwiatkowski A, et al. Common loss of-function variants of the epidermal barrier protein filaggrin are a major predisposing factor for atopic dermatitis. Nat Genet. 2006; 38(4):441-6.
- Clar EJ, Fourtanier A. Pyrrolidone carboxylic acid and the skin [in French]. Int J Cosmet Sci. 1981; 3(3):101
- Pyrrolidone carboxylic acid and the skin. E. J. Clar, A. Fourtanier Int J Cosmet Sci. 1981 Jun; 3(3): 101–113. doi: 10.1111/j.1467-2494.1981.tb00275.x
- Jacobson TM, Yüksel KU, Geesin JC, et al. Effects of aging and xerosis on the amino acid composition of human skin. J Invest Dermatol. 1990; 95(3):296-300.
- Jokura Y, Ishikawa S, Tokuda H, et al. Molecular analysis of elastic properties of the stratum corneum by solid-state 13C-nuclear magnetic resonance spectroscopy. J Invest Dermatol. 1995; 104(5):806-12.
- Rawlings AV, Davies A, Carlomusto M, et al. Effect of lactic acid isomers on keratinocyte ceramide synthesis, stratum corneum lipid levels and stratum corneum barrier function. Arch Dermatol Res. 1996; 288(7):383-90.
- Harding CR, Watkinson A, Rawlings AV, et al. Dry skin, moisturization and corneodesmolysis. Int J Cosmet Sci. 2000; 22(1):21-52
- Lodén M. Role of topical emollients and moisturizers in the treatment of dry skin barrier disorders. Am J Clin Dermatol. 2003; 4(11):771-88
- Rawlings AV, Harding CR. Moisturization and skin barrier function. Dermatol Ther. 2004; 17(suppl 1):43-8