One of the main functions of the epidermis is to create a barrier between the internal environment and the external environment, protecting us from dehydration.
Our body is mainly composed of water (55-65% in relation to age), that is about 42 kg in a 70kg man in good physical shape.
For the survival of the individual, given the vital importance of body water, it is essential that the water content is kept constant. The skin is therefore very important, as it is opposed to an excessive water dispersion in the environment. Despite this, a fair amount of body water is eliminated daily through the skin. This phenomenon is called insensitive transpiration or perspiratio insensibilis, insensitive because we do not realize it.
The loss of body water through the skin increases dramatically in the event of a burn. In the damaged area the water loss is considerable and, if it is quite extensive, it compromises the vital functions of the organism.
The term " perspiratio insensibilis" commonly indicates the physiological loss of water through the skin or the respiratory tract. Skin water loss should not be confused with sweat, because while perspiratio is a passive passage, sweating is an active glandular secretion, which requires a certain energy expenditure.
The respiratory losses are instead linked to the abundant water vapor content of the exhaled air.
Under basal conditions, water losses related to perspiratio insensibilis amount to about 700 ml per day. Even if we do not realize it the elimination of water is therefore consistent, one more reason to emphasize, once again, the importance of adequate fluid intake with the diet.
It must also be considered that this loss can increase, for example, during sports activity. An organism engaged in physical exertion eliminates more water, because the frequency of breathing increases and above all because the loss of water through the skin is clearly higher. In fact, the evaporation of water removes heat from the body, participating in the thermoregulatory mechanisms, with the aim of maintaining internal homeothermia.
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