Olga Andrienko, general practitioner, family medicine, cosmetologist-esthetician, national methodologist of the company “Renew Ukraine”

The key unifying word for these two conditions is “water,” but the level of deficiency is completely different. By the term “dry skin” we mean the dryness of the stratum corneum of the epidermis, and the concept of dehydration is clearly associated with the state of the water balance of the dermis. Consequently, approaches to eliminating dry skin will be completely different.

Let's start with the stratum corneum - the most significant structure for retaining moisture in the skin. The cells of the stratum corneum of the epidermis are in a special state; it is often called “dead,” although this is not entirely correct. The stratum corneum provides the correct level of TEWL (transepidermal water loss) within 3-4 g/h per 1 cm2. TEWL is an absolutely healthy physiological process that ensures renewal of the stratum corneum. A constant one-way flow of water through the epidermis ensures an influx of water-containing ions to the cells, a normal level of functioning of the enzymatic system of the epidermis and the imperceptible exfoliation of keratinized particles from the surface of the skin. There is very little water in the stratum corneum compared to other so-called “living” layers, only 15%, which contributes to a very easy and rapid loss of its own moisture. This is prevented by the lipid barrier and moisture-retaining structures of the epidermis. These include:

- natural moisturizing factor (NMF - Natural Moisturizing Factor) - hygroscopic molecules concentrated around the horny envelopes of corneocytes. Up to 40% of NMF are amino acids, as well as lactic acid, urea, sodium pyroglutamate;

- keratin;

- sebum – sebum that provides natural occlusion.

Based on the above, we can conclude that the concept of dry skin means dryness of the stratum corneum of the epidermis. Most often this is due to a violation of the moisture-retaining structures of the epidermis and its barrier properties. The reasons for this may be various factors: aggression from the external environment, improper care, damaging cosmetic procedures with improper rehabilitation, and internal causes affecting the condition of the skin.

The symptoms that appear when the stratum corneum is dry are associated with a violation of its renewal: roughness, flaking, a feeling of tightness. Subsequently, as the process worsens, increased sensitivity, irritability, and reactivity of the skin appear, superficial wrinkles form, facial tone is disturbed, the skin looks dull and has an uneven color. This situation can happen to any type of skin – oily, normal, combination and dry. Yes, yes, there is such a thing as “dry dry” skin, where the first “dry” is the type of skin by nature, and the second word “dry” means the condition of the skin at the moment. When the stratum corneum is dry, all methods of topical application of cosmetics and any procedures aimed at moisturizing, nourishing and restoring the barrier properties of the epidermis work well. These same treatment methods may be ineffective for dehydrated (dehydrated) skin, as there is a violation of the dermal matrix. This condition is associated with a decrease in the level of glycosaminoglycans in the dermis, fibrosis, and the accumulation of AGEs products (end products of glycation - the process of binding sugars to proteins, which disrupts the structure of the latter).

It is quite difficult to visually assess the condition of the dermis, but upon palpation we observe a violation of skin turgor and elasticity (rotation test, skin fold test). Dehydrated skin looks flabby and slightly yellowish due to impaired microcirculation. There may not be a large number of wrinkles, but those that exist lie quite deep, gradually forming creases. What is most interesting is that the barrier properties of the epidermis may not be affected; the skin can easily tolerate all procedures and stages of care and is not sensitive or reactive. Superficial application of cosmetics in such a situation will not bring the desired effect; correction is possible using injection delivery methods and, possibly, hardware implementation, for example, using electroporation.

A combination of both dryness of the stratum corneum and dehydration of the dermis is often encountered in the practice of a cosmetologist. In such a situation, a tandem of cosmetic care in compliance with all the principles of moisturizing therapy and a deeper dermal effect using mesotherapy works ideally. Of course, by combining treatment with lifestyle modification and correction of internal conditions that affect skin hydration, excellent results can be achieved. We will talk about this in the following articles.