image:Tewameter Principle.png, Principle of an instrument measuring transepidermal water loss. Water vapor is diffusing through the transparently shown cylinder. The yellow arrow symbolizes the diffusion direction. The two dark red square elements are two pairs of sensors each measuring relative humidity and temperature. Transepidermal water loss (TEWL or TWL) is the loss of water that passes from inside a body (animal or plant) through the epidermis (that is, either the epidermis, epidermal layer of animal skin or the epidermis (botany), epidermal layer of plants) to the surrounding atmosphere via

diffusion Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemica ...

and evaporation processes. TEWL in mammals is also known as insensible water loss (IWL), as it is a process over which organisms have little physiologic control and of which they are usually mostly unaware. Insensible loss of

body water In physiology, body water is the water content of an animal body that is contained in the tissues, the blood, the bones and elsewhere. The percentages of body water contained in various fluid compartments add up to total body water (TBW). This ...

can threaten

fluid balance Fluid balance is an aspect of the homeostasis of organisms in which the amount of water in the organism needs to be controlled, via osmoregulation and behavior, such that the concentrations of electrolytes ( salts in solution) in the various b ...

; in humans, substantial

dehydration In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mil ...

sometimes occurs before a person realizes what is happening. Measurements of TEWL may be useful for identifying skin damage caused by certain chemicals, physical insult (such as " tape stripping") or pathological conditions such as

eczema Dermatitis is inflammation of the skin, typically characterized by itchiness, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become thickened. The area of skin involved can ...

, as rates of TEWL increase in proportion to the level of damage. However, TEWL is also affected by environmental factors such as humidity, temperature, the time of year (season variation) and the moisture content of the skin (hydration level). Therefore, care must be taken when interpreting the meaning of TEWL rates.

Implications

Human health

From a clinical standpoint, TEWL measurements are of great importance in evaluating skin barrier functionality. Often normal rates of TEWL – from 2.3 g/(m²h) to 44 g/(m²h)Jan Kottner, Andrea Lichterfeld, Ulrike Blume-Peytavi (2013) ''Transepidermal water loss in young and aged healthy humans: a systematic review and meta-analysis'', Arch Dermatol Res Vol. 305 pp. 315–323, – are compromised due to injury, infection and/or severe damage as in the case of burns causing rates over 50 or even over 100 g/m²/h.K.L. Gardien, D.C. Baas, H.C. de Vet, E. Middelkoop (2016) ''Transepidermal water loss measured with the Tewameter TM300 in burn scars.'' Burns Vol. 42(7) pp. 1455-1462, Damage to the stratum corneum and superficial skin layers not only results in physical vulnerability, but also results in an excess rate of water loss. Therefore,

metabolic acidosis Metabolic acidosis is a serious electrolyte disorder characterized by an imbalance in the body's acid-base balance. Metabolic acidosis has three main root causes: increased acid production, loss of bicarbonate, and a reduced ability of the kidneys ...

, and conditions such as anhydremia or concentration of the blood are often critical issues for healthcare providers to consider in the treatment of burn patients. TEWL is of major concern in public health, considering the relatively high rate of burn incidence among communities in the developing world due to poor quality cooking stoves. Resources for burn care in local clinics are often scarce and depending on the affected surface area, TEWL is a major issue that can be overlooked. Furthermore, TEWL is also affected by variations in sweat gland activity, temperature, and metabolism. Therefore, transepidermal water loss becomes a significant factor in dehydration associated with several major disease states.

Botany and earth science

The amount of water that trees and other plants move from the ground to the atmosphere with TEWL is of interest in botany and earth science, as

transpiration Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth ...

by plants is a substantial component of the

water cycle The water cycle, also known as the hydrologic cycle or the hydrological cycle, is a biogeochemical cycle that describes the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly cons ...

on Earth.

Acronym variation

Web

corpus Corpus is Latin for "body". It may refer to: Linguistics * Text corpus, in linguistics, a large and structured set of texts * Speech corpus, in linguistics, a large set of speech audio files * Corpus linguistics, a branch of linguistics Music * ...

searches show that the acronym ''TEWL'' is about 40 times more common than ''TWL'' in reference to transepidermal water loss. A large advantage of ''TEWL'' is that it has higher specificity to that

sense A sense is a biological system used by an organism for sensation, the process of gathering information about the world through the detection of stimuli. (For example, in the human body, the brain which is part of the central nervous system re ...

than does ''TWL'', which has more alternative senses, including, most importantly, two other senses having to do with evaporation of

thermal work limit Thermal Work Limit (TWL) is defined as the limiting (or maximum) sustainable metabolic rate that well-hydrated, acclimatized individuals can maintain in a specific thermal environment, within a safe deep body core temperature (< ) and sweat rat ...

(TWL), which is the highest sustainable metabolic rate that well-hydrated, acclimatized individuals can maintain in a specific thermal environment, and total water loss (TWL), which in its physiologic sense is a superset of transepidermal water loss, because it also includes respiratory losses and urinary losses. Use of the acronym ''TEWL'' for transepidermal water loss avoids this ambiguity. As with many other acronyms in biology and medicine (for example, polymorphonuclear MN bronchioloalveolar carcinoma AC dolutegravir TG, there is no law preventing the letters of the acronym from representing combining forms (''trans-'' + ''epidermal'') or other syllables irrespective of word boundaries. For certain regions of human epidermis specific acronyms for TEWL are common. Water loss through finger and toe nails is called ''transonychial water loss'', abbreviated TOWL.Krönauer C., Gfesser M., Ring J., Abeck D.: ''Transonychial water loss in healthy and diseased nails.'' Acta Derm Venereol. (2001) 81(3):175–177.

References

External links

* {{YouTube , id=Elsoay13Lco , title=Transepidermal Water Loss Skin physiology Skin tests