Transepidermal Water Loss and Skin Barrier Function
The Tewameter® TM 300 (previous model of the Tewameter® TM Hex) with its “open chamber” principle is the worldwide most accepted measuring device for the assessment of the Transepidermal Water Loss (TEWL). This is an indispensable parameter for the evaluation of the water barrier function of the skin and a basic measurement in all kinds of applications. Even the slightest damage in the skin water barrier can be determined at an early stage.
A certain evaporation of water from the skin takes always place as part of the normal skin metabolism. However, as soon as the barrier function of the skin is slightly damaged, the water loss will increase (even with smallest damages invisible to the human eye). Therefore this measurement is a basis for all cosmetic and dermatological research. The Tewameter® probe measures the density gradient of the water evaporation from the skin indirectly by the two pairs of sensors (temperature and relative humidity) inside the hollow cylinder. This is an “open chamber” measurement. This method is the only to assess the TEWL continuously without influencing its micro environment. The measured values express the evaporation rate in g/h/m2.
A = surface [m2]m = water transported [g]
t = time [h]
D = diffusion constant [= 0.0877 g/m(h(mmHg))]
p = vapour pressure of the atmosphere [mm Hg]
x = distance from skin surface to point of measurement [m]
The Tewameter® TM 300 is used in the Multi Display Devices (MDD).
Probe Heater PR 100
The sensors of the probe normally have room temperature (20-22°C), whereas skin temperature is 30°C and higher. As the amount of evaporating water measured with the device is extremely small (healthy skin 8-15 g/h/m² → 0.000001333 - 0.00000025 g/minute/cm²), the sensors inside the probe should reach skin temperature to measure this small amount exactly and stable. With the Probe Heater PR 100, the probe head is constantly warmed up to a temperature close to skin temperature and thus getting very quickly accurate and stable results.
sensors inside the probe cold (room temperature) sensors preheated to 30°C - stable measurement in an extremely short time