Everything you need to know about cutaneous xerosis.

The deterioration of the skin barrier observed in cases of xerosis results from internal and external factors that disrupt the skin's hydrolipidic balance. The first factor is age. Indeed, over time, the production of ceramides, cholesterol, and fatty acids, essential components of the intercellular cement, decreases. This scarcity weakens the cohesion of the corneocytes, making the skin more permeable to water evaporation. Simultaneously, sebum secretion slows down, which weakens the hydrolipidic film.

Environmental conditions also play a significant role. A cold and dry air, whether in winter or due to inappropriate air conditioning, accelerates water loss by disrupting the lipid structure of the stratum corneum. Additionally, wind and exposure to UV rays damage epidermal lipids, particularly polyunsaturated fatty acids, leading to a degradation of the barrier function and a reduced ability of the skin to retain moisture.

Finally, certain daily habits can exacerbate xerosis, or dry skin. The overly hot showers dissolve the protective lipids of the hydrolipidic film, making the skin more vulnerable to external aggressions. The use of certain soaps, particularly those containing sulfates like sodium lauryl sulfate (SLS), further damages the skin barrier by eliminating epidermal lipids and altering the skin's pH, which weakens the enzymes involved in the maturation of cells in the stratum corneum, or outermost layer of the skin.

The cutaneous xerosis can be effectively managed through the regular and long-term use of moisturizing and nourishing creams. The solutions to xerosis are based on three main types of active ingredients: humectants, film-forming agents, and emollients, each acting at their level to restore the integrity of the skin barrier.

• The humectants : Humectants are substances that attract water into the skin. Glycerin is one of the most commonly used and effective humectants for xerosis, due to its high hygroscopicity, lipid-modulating activity, and corneodesmolytic effect, meaning it facilitates the maturation of the corneocyte envelope by transglutaminase. Glycerin also promotes skin hydration by attracting and retaining water in the superficial layers of the epidermis. Other humectants, such as urea or components of the NMF, are also frequently used to combat xerosis.

• The film-forming agents : Film-forming agents work by creating a protective layer on the surface of the epidermis, thereby preventing the evaporation of water from the skin and strengthening the hydrolipidic film. It should be noted that film-forming agents can be hydrophilic and have an affinity with water, or they can be hydrophobic and repel it. Hydrophilic agents, like carbohydrates, capture water molecules to create a hydrogel and form a hydrated film on the skin's surface. Hydrophobic film-forming agents, such as silicones, mineral or vegetable oils, and waxes, have a more occlusive effect and block trans-epidermal water loss more by opposing water molecules.

• The Emollients : Emollients are ingredients that soften and smooth the skin, while enhancing its elasticity and flexibility. More specifically, emollients promote the accumulation of water in the stratum corneum and strengthen the cohesion between the lipids in the intercellular space, particularly ceramides, to hinder the movement of water in the stratum corneum. Some of them, like vegetable oils, can insert themselves between the lipids of the stratum corneum and reinforce the barrier function of the epidermis.

The daily application of creams containing humectants, film-forming agents, and emollients can compensate for the lack of lipids and improve the hydration and barrier function of the skin. Scientists agree that a combination of hydrophilic and lipophilic molecules is preferable.

Product recommendations?

To care for dry to very dry skin, we offer at Typology a dermatological bar as well as a lipid-replenishing balm. Enriched with calendula extract and sweet almond oil, our dermatological bar gently cleanses the skin without compromising its hydrolipidic film. It is formulated at a neutral pH and does not contain soap or sulfates. As for our lipid-replenishing balm, it is a high-tolerance treatment providing continuous hydration for 24 hours, while reducing feelings of discomfort and spacing out periods of severe dryness.