Not all ‘dry’ skin follows the same rules. A walk through any skincare aisle will have the words “moisturizing” and “hydrating” jumping out at you in spades – leaping off labels of product after product promising each. The problem is that – while often used interchangeably in the skincare industry – dehydrated skin and dry skin are not the same.
When skin is hydrated, it means that skin cells have enough water content within them to swell, allowing them to remain plump and full of elasticity while reflecting light well. That’s why hydrated skin cells result in skin that is fresh, smooth, and vibrant. When the opposite occurs, when skin cells are not retaining enough water – or water leaks from the cell walls – they can constrict and shrink, leading to dull, flat skin.
Moisturized skin is equipped to trap and seal in moisture in the name of building the skin’s natural protective barrier. This allows skin to stay smooth and soft, but also means it prevents skin from being vulnerable to flaking and frequent dryness.
With a strong barrier, skin is able to prevent water loss. When moisture leaks from the stratum corneum - the outermost layer of the epidermis - skin is experiencing TEWL (transepidermal water loss). To prevent TEWL, the stratum corneum must be continuously supported and strengthened to be the skin's first line of defense.
Knowing the Difference
With the two terms used so interchangeably in skincare, how can you tell which one you need? Your skin’s appearance and condition is the tell all. If your skin is frequently dry and flaking, it’s an indication your natural lipid barrier is weakening. You should be favoring moisturizers in your skincare rituals to restore the water content necessary to support better barrier-building.
But skin doesn’t need to show signs of dryness to be suffering from dehydration. If you are battling an overall dullness or lack of luminosity in your skin, it’s a leading sign that hydrating products should be the heroes of your skincare routine. Hydrating products contain humectants such as hyaluronic acid, glycerine, saccharide isomerate and xylitol to name a few. Humectant bring water to stratum corneum not only by drawing water from the surrounding environment but also by bringing it up from deeper layers of the skin.
Ethnicity and Hydration: The Correlation
The correlation between hydration and ethnic background is a complex one, because how the amount of water loss and dehydration varies throughout the body is complicated. It can be influenced by a number of environmental factors.
Influential scientific studies of skin hydration among different ethnic groups have used TEWL, capacitance and conductance as a measurement of how effectively the skin’s barrier retains moisture, and how resiliently skin cells hold water content to stay hydrated. The common finding is that darker skin pigmentation results in an elevated capacity of the stratum corneum to hold water, leading to better hydration, but the opposite was true for the strength of the skin barrier. Lighter skin tones had a naturally superior barrier function, while darker skin tones experienced much higher rates of TEWL.
How your skin pigmentation plays a part in your skin’s natural hydration informs the skincare routine that’s going to be the most impactful. For ethnicities that have darker skin tones, ensuring your ritual pays particular attention to negating the effects of TEWL by keeping your natural lipid barrier strong is paramount.
But just like not all dry skin follows the same rules – all melanated skin is not created equal. Hydration shouldn’t be neglected in caring for darker skin pigmentations. Melanated skin care is a dynamic dance of both. The key is finding a balance – coordinating hydration and moisturization – and educating yourself on your skin’s own warning signs.
Racho, Janeca. Hydrator vs. Moisturizer: What’s the Difference and Which One Do You Need? https://www.dermstore.com/blog/hydrating-vs-moisturizing/
Voegeli et al. International Journal of Cosmetic Science. 2019 Facial skin mapping: from single point bio-instrumental evaluation to continuous visualization of skin hydration, barrier function, skin surface pH, and sebum in different ethnic skin types.
Plessis et all. International guidelines for the in vivo assessment of skin properties in non-clinical settings: Part 2. transepidermal water loss and skin hydration. Skin Research and Technology. 2013.
Tagami, H. Location-related differences in structure and function of the stratum corneum with special emphasis on those of the facial skin. International Journal of Cosmetic Science. 2008
Diridollou et al. Comparative study of the hydration of the stratum corneum between four ethnic groups: influence of age.