Skin Dryness - a Common Issue
Water is an essential substance for life and serves many functions, including within the skin. It acts as a building block in tissues and cells, creates an environment for metabolic reactions in the body, regulates body temperature, and transports nutrients within the system. When we are healthy, our skin contains about 20% of the water within our body. Depending on the depth, its content varies - in the stratum corneum (the outermost layer of the skin), it should not be less than 10%. When the water content in this layer drops below the appropriate level, we experience weakened cell adhesion and the effect of roughness and flaking.
So, how can we ensure proper moisturization? Is it enough to provide the skin with moisturizing ingredients? Will drinking plenty of water hydrate the skin? We need to be aware that the problem of dry skin is complex. The skin's moisture level, responsible for its proper tension, depends on the amount of water we supply externally and internally but also on the skin's ability to retain it.
The skin acts as a barrier, and its ability to retain water is assessed by determining the TEWL value - Transepidermal Water Loss. This parameter depends on many factors. Moreover, a crucial element in this regard is the NMF - Natural Moisturizing Factor, a mixture of substances present in corneocytes (skin cells). NMF retains water in cells and serves a protective role against external factors.
One widely known component of NMF is urea, which we associate with exfoliation. Indeed, in skincare products designed for callused skin, concentrations above 15-20% will exfoliate, but in lower concentrations, it binds water without disrupting intercellular connections (and thus, exfoliation). Studies show decreased urea content in the epidermis of individuals with dry skin, psoriasis, or atopic dermatitis.
Another important factor affecting skin moisture is the presence of superficial lipids. Water "escapes" from the epidermis through evaporation. Proper proportions between the components of the epidermal lipid barrier enable it to fulfill its function and limit water loss. Ceramides, ensuring coherence between corneocytes, are crucial lipids.
In dermatology, the terms 'skin dryness' and 'dehydration' are not synonymous. Dry skin is typically considered a pathological condition, manifesting as excessive flaking, roughness, a tendency for the epidermis to crack, and redness. Intensifying dryness might lead to itching, soreness, and burning sensations. However, when the skin lacks water and proteins that bind it (e.g., profilaggrin, loricrin), the stratum corneum loses its integrity, but this doesn't necessarily entail the typical symptoms of dry skin.
To alleviate dry skin, it's beneficial to use skincare products containing:
- Humectants - compounds with the ability to bind water, retaining it in the skin. Examples include urea, hyaluronic acid, amino acids, glycerin, and lactates.
- Occlusive agents - forming a physical barrier for evaporating water. Substances like vaseline, lanolin, mineral and silicone oils form a "film" on the skin's surface.
- Lipid-supplementing substances - ceramides, cholesterol, triglycerides, and fatty acids that naturally occur in the skin.
- Ingredients aiding the removal of dry superficial skin scales, e.g., polyhydroxy acids and lactobionic acid.
Emollients are essential in the care of dry and dehydrated skin. They combine hydrophilic (water-loving) and lipophilic (fat-loving) ingredients to retain water, form an occlusive layer on the skin's surface, replenish lipids in the hydrolipidic barrier, and often contain regenerating and anti-inflammatory agents. However, not all advertised as safe for dry and sensitive skin are devoid of potentially irritating ingredients. Pay attention to the INCI list for artificial colorants, fragrances, and the presence of hydro- and lipophilic components.
To restore the proper function of the skin's hydrolipidic barrier, it is crucial to limit factors that disrupt it and enhance daily care efficacy. Knowing the lipids that form the stratum corneum and support its protective functions, incorporating products based on these fats into skincare helps the skin function correctly, defend against microbes, and reduce susceptibility to irritation.
Plant-based oils in cosmetics have numerous advantages. Rich in essential unsaturated fatty acids and bioactive compounds, they exhibit not only emollient (softening, moisturizing) but also anti-aging, regenerative, anti-inflammatory, and sebum-regulating properties.
Chronic dryness:
- Increases susceptibility to external factors like radiation, microbes, temperature, minor injuries, detergents.
- Reduces skin elasticity.
- Causes an unaesthetic appearance: rough, matte, flaky.
- May lead to itching and burning sensations.
- Increases sensitivity.
TEWL level depends on various factors: gender, age, temperature, perspiration, body area, emotional state, humidity, air temperature, and airflow speed surrounding the skin."