Psoriasis is a provoked disease. This means that the skin
reacts to various kinds of irritations with an accelerated and enhanced
formation of cells of its upper layer (epidermis). At the same time, the time
of division of these cells is reduced from about 18-20 to 1-2 days. The time
during which the newly formed cells of the epidermis must reach the surface of
the skin and go through many stages of development is also reduced from the
norm of 21-28 to about 3-4 days. The shortening of the period of cell
development leads to a violation of the formation of structures that stabilize
tissues, and, in this regard, to a typical violation of the keratinization of
the upper layer of the skin. Against the background of many times accelerated
cell division, massive thickening of the skin appears in the affected areas and
there is an increased exfoliation of its upper layers.
Exfoliation leads to roughening of the skin and to the loss of its natural
protective functions. An increased return of moisture and fat begins,
accompanied by a pronounced feeling of dryness and fragility of the skin. The
loss of the skin’s natural acid mantle allows bacteria and fungi to enter,
which often cause itching. The thin network of blood vessels located in the
dermis, which serve to nourish the tissue, must adapt to the thickening of the
epidermis. In this regard, blood vessels penetrate further into the upper
layers of the skin. This leads to reddening of diseased areas of the skin and
an increase in the vulnerability of blood vessels. These changes occurring in
the epidermis are accompanied by inflammatory processes in the deeper layers of
the dermis. At the same time, cells and substances that contribute to the
development of inflammation migrate to both layers of the skin. The reason why
there is an increased reproduction of cells and the activation of substances
that promote inflammation has not yet been established.