The skin is our largest organ which, apart from being a physical barrier from the environment, also protects with a chemical barrier. A chemical barrier consists of the epidermis, the most important layer of it being the stratum corneum, with all its belonging components. The barrier function of the skin therefore depends on the skin`s pH value (on the surface), composition and orderliness of the lipid layer of the skin and its level of moisture content, skin microbiota and the activity of the enzymes, which all affects the course of physiological processes in the skin. If the skin`s barrier is not adequate, the pathogens from the environment can enter the skin, evaporation of water is increased and the skin becomes dry, which makes it incapable of performing the functions needed for the correct build and cohesion of the skin barrier. The skin barrier can also be negatively affected by various skin diseases. Therefore, we have two groups of structural abnormalities of the skin barrier, the primary group being where the structural abnormality is caused by gene defects, and the secondary group of structural abnormalities which are caused by environmental factors. Within these two groups, different diseases are found; atopic dermatitis, psoriasis and ichthyosis. These three diseases have in common that the key components and processes that are important for the correct build of the skin barrier are negatively affected in many ways. Basic care of the affected skin by any of the three diseases is achieved by the use of cosmetic products which are made of ingredients that encourage the regeneration of the skin barrier and increase the hydration of the epidermis. The treatment of the said diseases is based on local therapy in milder forms of the disease, in case of a severe form of the disease, the treatment is a combination of local therapy, systemic treatment and some other approaches for the treatment of skin diseases.
There are many different products on the market which contain different ingredients for the regeneration of the skin barrier. We have examined in more detail 13 skin care products which are intended for skin with atopic dermatitis, 11 skin care products intended to relieve the symptoms of psoriasis and 9 skin care products for skin ichthyosis. These products were then divided into two groups, one for products that are intended for daily skin care, and the other for products intended for skin cleansing. We have found that all examined products for all three diseases use ingredients with moisturizing action, which was in line with our expectations. The most commonly found were emollients, which fill the open spaces between the cells in the stratum corneum and in that way prevent excessive skin peeling and increase the hydration of skin, followed by humectants and then occlusives. They were all found in products for skin care of inflammatory diseases and also in products for skin cleansing; however, the occlusives were rarer in the latter group of products. The use of vegetable oils that contain unsaturated fatty acids (γ – linolenic, linoleic, palmitooleic) which exhibit special effects on skin with a damaged barrier is a bit more common in products made for treatment of atopic dermatitis.
In accordance with the theoretical fundamentals, we have examined the presence of keratolytics in cosmetic products, which are used to reduce hyperkeratotic lesions on the skin. They were only found in skin care products for skin with psoriasis and ichthyosis. Cosmetic products for care of atopic skin do not contain keratolytics because the hyperkeratotic lesions on the skin are not specific for them. The most commonly used keratolytic is salicylic acid, which is a type of beta and aromatic hydroxy acids and allows reducing of the thickening of lesions on the skin as it affects the easier exfoliation of cells in the epidermis.
We have found the biggest differences between the products intended for skin care with different inflammatory diseases in the use of active ingredients. Common to all is an ingredient called nicotinamide, which is an active form of B3 and it has been proved that it increases the hydration of the epidermis, affects the synthesis of keratin, filaggrin and ceramides in the stratum corneum. We have also found out that the active ingredients are rarely present in products for ichthyosis, as it is typical in products for atopic dermatitis and psoriasis.
Pre-, pro- and postbiotics are added to cosmetic products predominantly for the purpose of regulating a healthy skin microbiota. They are one of the latest approaches to maintaining a healthy skin barrier function and at the same time take care of skin with a damaged skin barrier. In accordance with this, we have come across products on the market which contain thermal water with selenium and colloidal oat extract, which are prebiotics. These are mainly oligosaccharides, sugar alcohols and complex polysaccharides, which are food for commensal bacteria and promote the colonization of the skin with a healthy microbiota.