The skin forms the outer protective layer of the human body. It is an association of different cell types and built up in layers, living, metabolically active cells in the depths, sensory cells for the sense of touch and temperature, and dry horny cells as the top layer. The skin is a fascinating interplay of different processes and numerous biological strategies to achieve the best possible protective function. To care for the skin optimally, it makes sense to know the most important processes and elements of this interplay, to support them and to disturb them as little as possible.
First, there are the skin cells, which we feel as tissue. For a long time, they were in the foreground when talking about the skin. Then there are substances that are important, such as the lipid layer formed by the skin, a mixture that leaks out through the pores of the skin and "melts" as a fine film. It not only keeps the outer skin supple, thus protecting it from cracks, but also has an immunologically active effect. The substances on the skin include substances secreted by the skin that determine the pH value, which is called the protective acid mantle. In the recent past, the microbiome of the skin has gained more and more attention since the importance of bacteria in the interaction with the whole organism and especially with the immune system is becoming better understood. Bacteria live on the surface of the skin with which we live in symbiosis in the same way as in the large intestine and other parts of the body. Every person has their own specific, healthy bacterial flora, which is made up of different strains of bacteria. They are an essential part of skin health and must be integrated into our skin care routine. They can be sensitively disturbed by substances in skin care products. Thus, the lipid layer, acid mantle and the microbiome of the skin form a layer that is important and lies on top of the actual skin cells. Then, from the outside in, different cell layers follow.
In recent years, spectacular insights have been gained into the immune system of the skin, which have contributed decisively to a better understanding of possible disturbances of this fine interplay. This is the prerequisite for us to be able to develop more and more suitable skin care products that better respect the conditions of the body and that interfere less with the well-rehearsed interaction of the various elements than was the case in the past due to ignorance. This contributes decisively to the preservation of skin health. For every disturbance in one part influences the stability or even susceptibility to skin diseases.
For example, the balanced colonisation with certain bacterial strains ensures that no foreign bacteria, viruses, or fungi can settle. One's own native bacterial flora thus ensures that the immune system does not even have to actively fight off pathogenic organisms. However, if this flora is disturbed, for example by excessive care or by preservatives in body care products, this flora can be damaged and can no longer fulfil this defense function. Also, if permanently added substances cover the skin, the acid mantle can be altered, which in turn shifts the balance of the various bacterial strains.
Knowledge of different cell types that actively contribute to the skin's immune system is becoming increasingly differentiated. These migrate through the network of skin cells and enable specific reactions once the skin is damaged or attacked. The interaction of all the processes in the skin are so important and diverse that a new field has formed: dermatoimmunology. This field also includes wound healing, which is closely connected with the immune system and the actual skin metabolism as well as the regenerative capacity of the cells. Accordingly, the complex immune system of the skin enables not only effective protection against pathogens, but also rapid wound healing, constant regeneration, and the development of tolerance to harmless antigens.
For their part, skin care and the cosmetics manufacturers who develop the necessary products have the opportunity but also the responsible task of integrating this knowledge into the products and refraining from doing anything that would disrupt this fascinating interplay. Sun protection products play an important role here on several levels: they directly protect the skin from UV damage and thus contribute directly to maintaining health. Sunburn is a serious skin damage that, if repeated, demonstrably increases the susceptibility to skin cancer (melanoma). At the same time, the substances contained in the sunscreen must not disturb the skin processes. Especially in the heat of sun exposure, when bathing or in the mountains, the skin must perform at a high level to maintain its own stability. That is why sun protection products must be finely tuned to the needs of the skin: they themselves are "high-performance products" that must be scientifically well-founded and constantly reassessed. They are intended to provide additional protection, protection from UV rays, but must not disrupt the interaction of the skin's various processes.
Urs Pohlman MD PhD