Skin Moisture Barrier and Trans-Epidermal Water Loss

Updated: Jul 15

Did you know that your skin, if laid flat, would take up an area of around 2 square metres? This make skin the largest organ of our body, and an important one at that.

Skin Protective Barrier

Our skin's major function is to create a strong, flexible barrier between what constitutes us and the external environment. Having evolved from simple aquatic organisms, the transition our ancestors made to life on dry land required a waterproof barrier, in order to protect our moisture-rich interior from drying out. This is where the skin comes in: we wouldn’t last a moment without it, which makes it an organ as vital as our heart of lungs.


Dry skin as a result of trans-epidermal water loss
Skin with barrier integrity damaged vs healthy skin

Transepidermal water loss (TEWL) occurs when water from our skin evaporates into the surrounding environment. More water evaporates from skin whose barrier has been compromised. Broken skin barrier and TEWL have been shown to be correlated to skin ageing, more pronounced appearance of fine lines and wrinkles, as well as sensitivity to skin irritation, which studies show to be increased especially in post-menopausal women. High levels of TEWL are also linked to skin dryness, acne, atopic dermatitis (eczema), rosacea and psoriasis.


Let’s focus on the vital moisture barrier then. It is maintained in skin's outermost layer, the stratum corneum, which consists of about 10–20 layers of cells embedded in a lipid (fatty) mixture; this ensures skin's water tightness. This barrier can be damaged mechanically (cuts, burns etc.) or chemically. Pollution, UV exposure, over-exfoliating and applying too many strong actives in skincare routines can damage the lipid barrier, as can using harsh detergents such as sodium lauryl sulfate (SLS). Unfortunately, the alcohol present in hand sanitisers can also compromise our hands' protective barrier.

What has a positive effect on skin barrier function?

Products for very dry hands

In short, moisturising. This simple action can restore the integrity of the stratum corneum, replace the skin lipids, reduce TEWL, help prevent dry skin and loss of elasticity, reduce fine lines, smooth and maintain skin's healthy appearance.


As moisturising substances go, hydrating humectants and smoothing emollients are the types that we tend to think are best, but, while essential and very effective, they can often evaporate into thin air if not aided by an occlusive element of a moisturiser. Occlusive substances are oil-based, water repellent, have a thicker texture and form a protective film which can actually help rebuild or strengthen the lipid barrier of the skin. Examples include petroleum jelly, silicones, or - our plant-based favourite - Shea butter. So, in short, hydrating our skin is super-important, but so is sealing that moisture in. Humectants’ job is to pull moisture from the environment to the skin to hydrate and plump it, emollients’ is to condition and soften it, while an occlusive’s job is to create a waterproof barrier and prevent TEWL. Good moisturisers will have all three elements, but you can also use a more occlusive product on top of a light moisturiser, an essence, or a water-based serum. Such occlusive products include ointments, balms or facial oils.


Solid Hand Cream

At Blanka Soap, we design our products to respect and reinforce the natural skin barrier. Our recent bestseller, the Magic Hand Balm, contains light moisturisers packed with antioxidants: vitamin E, organic Rice, Sunflower and Grape-seed oils, as well as more occlusive butters: Shea, Cocoa and Mango.

Our soaps are rich in one of the best humectants, glycerine, and are formulated with extra fatty content which doesn’t end up being turned into soap (saponified). It is present in the finished bar, the main ingredient of this ‘leftover’ lipid portion being the fantastic Shea butter.