Dry and Dehydrated Skin

Skin dryness and dehydration are common, and although they are separate skin concerns the two are closely linked^2,5.  If the skin is dry it will inevitably lead to dehydration, and if the skin is dehydrated, it can lead to skin dryness^2,11.  Dehydration refers to a lack of water in the skin, whereas dryness refers to a lack of skin lipids and water due to a poorly functioning skin structure and physiology^4,8,11.

Keeping the skin hydrated is essential as all biological processes, even those within the skin, rely on its presence^1,4,11.  Without skin hydration, enzymes required for skin cell production and barrier function maintenance cannot function optimally leading to the formation of dry skin^4,10,11.

The ability of the skin to maintain hydration relies mostly on two aspects:

1. The natural moisturising factor within the skin and its ability to hold water
2. The barrier function of the skin^1,5,10,11

Skin hydration is also influenced by the amount of sebum present on the surface of the skin, acting an extra barrier to water loss^1,3.  Within the second layer of the skin, the dermis, it is hyaluronic acid that is important for the maintenance of hydration in this region¹¹.

Causes of skin dehydration and dryness may include:

• Air-conditioning: these systems reduce environmental humidity when used in both cooling and heating states, which draws water from the skin^1,2,5,10,11
• Environmental and seasonal changes: low humidity, cold weather, exposure to wind^{2,4,5,8,9,10,11}
• Ageing: as we age our skin barrier depletes, physiological function decreases, sebum production slows and natural moisturising factor levels are decreased, hence skin dryness and dehydration may result^1,2,3,5,9,10
• UV exposure can lead to the decrease in production of filaggrin, which is an essential structural protein involved in developing our skin barrier lipids. Without these lipids, our barrier function is compromised hence it can become rapidly dehydrated and dry. UV exposure also decrease the levels of natural moisturising factor within the skin^1,5,8,10,11
• Hormones: during menopause as oestrogen and progesterone levels decline there is an increase in skin dryness and dehydration¹⁰
• Mechanical disturbance of the skin barrier: scratching, rubbing of clothes or injury^8,10
• Frequent skin washing with use of harsh detergents: can strip skin lipids and moisture via a reduction in the level of natural moisturising factor and skin lipids^2,8,9,11
• Sodium lauryl sulphate and other detergents can increase water loss^2,8,9
• Chronic diseases such as psoriasis, atopic dermatitis and diabetes^1,2,5,8,10
• Malnutrition inclusive of a low protein diet¹⁰
• Psychological stress^4,10
• Medications¹⁰

Symptoms of dry skin may include:

• Scaly, flaky, rough skin
• Faint inflammation
• Dullness
• Itching
• Redness
• Tightness
• Skin cracking
• Increased incidence of skin tears, infection, dermatitis and pressure ulcers especially in the elderly^{2,3,4,5,8,9,10,11}

Treatment for dry and dehydrated skin is firstly focussed on prevention and then followed by maintenance^2,3,5.  The optimal strategy involves moisturisation through the application of topical skincare products to rehydrate and nourish the skin, with a focus on repairing the skin barrier to reduce further water loss and subsequent dehydration^1,2,5,9,11.

Moisturisers have multiple actions on the skin and at various depths, depending on their formulation⁴.  They contain emollients and humectants, which soften and smooth, and draw water and hold it into the skin respectively⁴.  Skin cells can swell up to 50% when they are fully hydrated, such as in a humid environment⁶.  When the skin is hydrated, it is more supple due to an improvement in flexibility, strength and elasticity^1,4,6.

To manage dry skin it is also important to use mild cleansers and avoid the use of soap due to its alkaline pH further drying out the skin^2,3.  When cleansing or washing the body, it is recommended to shower or bathe with lukewarm water to prevent further dehydration^2,3.

Common skincare ingredients incorporated into emollient and humectant moisturisers include glycerin, ceramides, macadamia oil, hyaluronic acid, dimethicones, triglycerides, cocnut oil, shea butter, olive oil, squalane, niacinamide, allantoin, urea, essential fatty acids, alpha hydroxyl acids, sodium PCA and vitamin E^2,3,4,8,9.

It is also suggested that drinking 6-8 glasses of water per day will influence skin hydration positively¹. There is minimal high quality research that has been performed in this specific area, however a common theme is that if you increase your water intake when previously it was low, it may lead to a small increase in skin hydration^1,7.

¹Akdeniz, M., Tomova_Simitchieva, T., Dobos, G., Blume_Peytavi, U., & Kottner, J. (2018). Does dietary fluid intake affect skin hydration in healthy humans? A systematic literature review. Skin Research and technology, 24(3), 459-465. doi: 10.1111/srt.12454

²Berardesca, E., Mortillo, S., Camelli, N., Ardigo, M., & Mariano, M. (2018). Efficacy of a shower cream and a lotion with skin-identical lipids in healthy subjects with atopic dry skin. Journal of Cosmetic Dermatology, 17(3), 477-483. doi: 10.1111/jocd.12668

³Lichterfeld-Kottner, A., Lahmann, N., Blume-Peytavi, U., Mueller-Werdan, U., & Kottner, J. (2018). Dry skin in home care: a representative prevalence study. Journal of Tissue Viability, (2018), 1-6. doi: 10.1016/j.jtv.2018.07.001

⁴Loden, M. (2003). Role of topical emollients and moisturizers in the treatment of dry skin barrier disorders. American Journal of Clinical Dermatology, 4(11), 771-788.

⁵Masaki, H., Yamashita, Y., Kuotani, D., Honda, T., Takano, K., Tamura, T., Mizutani, T,m & Okano, Y. (2018). Correlations between skin hydration parameters and corneocyte-derived parameters to characterize skin conditions. Journal of Cosmetic Dermatology, (2018), 1-7. doi: 10.1111/jocd.12502

⁶Mojumdar, E. H., Pham, Q. D., Topgaard, D., & Sparr, E. (2017). Skin hydration: interplay between molecular dynamics, structure and water uptake in the stratum corneum. Scientific Reports, 7(1), 1-13. doi: 10.1038/s41598-017-15921-5

⁷Palma, L., Marques, L. T., Bujan, J., & Rodrigues, L. M. (2015). Dietary water affects human skin hydration and biomechanics. Clinical, Cosmetic and Investigational Dermatology, 8(), 413-421. doi: 10.2147/CCID.S86822

⁸Proksch, E., & Lachapelle, J.-M. (2005). The management of dry skin with topical emollients – recent perspectives.  Journal of the German Society of Dermatology, 3(10), 768-774. doi: 10.1111/j.1610-0387.2005.05068.x

⁹Shim, J. H., Park, J. H., Lee, J. H., Lee, D. Y., Lee, J. H., & Yang, J. M. (2016). Moisturizers are effective in the treatment of xerosis irrespectively from their particular formulation: results from a prospective, randomized, double-blind controlled trial. Journal of the European Academy of Dermatology and Venereology, 30(2), 276-281. doi: 10.1111/jdv.13472

¹⁰Toncic, R. J., Kezic, S., Hadzavdic, S. L., & Marinovic, B. (2018). Skin barrier and dry skin in the mature patient. Clinics in Dermatology, 36(2), 109-115. doi: 10.1016/j.clindermatol.2017.10.002

¹¹Verdier-Sevrain, S., & Bonte, F. (2007). Skin hydration: a review on its molecular mechanisms. Journal of Cosmetic Dermatology, 6(2), 75-82. doi: 10.1111/j.1473-2165.2007.00300.x