Define water losses by Insensible perspiration?

Insensible perspiration accounts for a relatively constant amount of water loss that is proportional to the surface area of the body. It is so called because the evaporation takes place from the skin immediately and the water loss is not noticeable. As we have already seen, this evaporation is an important means by which body temperature is maintained. Infants have a much greater surface area relative to body weight than do adults; consequently, they are much more vulnerable to water loss from the skin and rapid changes in body temperature.