Contrary to all expectations, it is worth noting that there is no definition of normal skin, the latter being qualified in comparison with the other skin types: a normal skin is not a dry skin, not an oily skin, not a mixed skin, and no more a pathological skin.
A brief analysis of its structure and of its functions enables to draw a more positive definition of the normal skin.
At the more external level, there is a very thin protective epithelium that constitutes the epidermis. It plays the main part in protecting the organism against external aggressions, notably ensured through the cohesion of epithelial cells and the keratinocytes that undergo a specific process of differentiation as they migrate from the dermoepidermal junction to the skin surface. This cohesion results from intercellular ties caused by the desmosomes, which are mainly responsible for the very great mechanical resistance of the epidermis. However, the migration of the keratinocytes remains possible since these desmosomal ties are submitted to a continuous process of dissolution and reconstitution associated with a progressive decrease in their adherence strength.