Insensible perspiration is the loss of water through the skin which does not occur as perceivable sweat. Insensible perspiration takes place at an almost constant rate and reflects evaporative loss from the
epithelial cells of the
skin
Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation.
Other animal coverings, such as the arthropod exoskeleton, have different de ...
.
Unlike in
sweating, the fluid lost is pure water, i.e. no
solutes
In chemistry, a solution is a special type of homogeneous mixture composed of two or more substances. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent. If the attractive forces between the solvent ...
are lost. For this reason, it can also be referred to as "insensible water loss".
The amount of water lost in this way is deemed to be approximately 400ml per day.
Some sources broaden the definition of insensible perspiration to include not only the water lost through the skin, but also the water lost through the epithelium of the respiratory tract, which is also approximately 400ml per day.
Insensible perspiration is the main source of heat loss from the body,
with the figure being placed around 480 kCal per day, which is approximately 25% of basal heat production.
Insensible perspiration is not under regulatory control.
History
Known in Latin as ''perspiratio insensibilis'',
the concept was already known to
Galen
Aelius Galenus or Claudius Galenus ( el, Κλαύδιος Γαληνός; September 129 – c. AD 216), often Anglicized as Galen () or Galen of Pergamon, was a Greek physician, surgeon and philosopher in the Roman Empire. Considered to be one ...
in ancient Greece and was studied by the Venetian
Santorio Santorio
Santorio Santori (29 March, 1561 – 25 February, 1636) also called Santorio Santorio, Santorio de' Sanctoriis, or Sanctorius of Padua and various combinations of these names, was an Italian physiologist, physician, and professor, who introduc ...
,
who experimented on himself and observed that a significant part of the weight of what he ate and drank was not excreted in his faeces or urine but was also not being added to his body weight. He was able to measure the loss through a chair that he designed.
References
Excretion
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