ABSTRACT
The main function of skin is to serve as barrier at the interface between body and
environment. This is manifested in different ways, e.g., as a barrier to mechanical
stress, to UV-light damage, and to the penetration of drugs, allergens, microorgan-
isms, toxic substances, etc. For many dermatological patients, the skin may also
represent a strong social barrier. However, from an evolutional point of view, the
single most important task of skin is to create a watertight enclosure of the body to
prevent water loss. Water homeostasis is a strict requirement for normal body
function as an uncontrolled loss of water results in a dramatic increase in ion
concentrations with consequent harmful effects on cells and tissues.
