STUDY OF THE STRATUM-CORNEUM BARRIER FUNCTION BY TRANSEPIDERMAL WATER-LOSS MEASUREMENTS - COMPARISON BETWEEN 2 COMMERCIAL INSTRUMENTS - EVAPORIMETER(R) AND TEWAMETER(R)

The measurement of transepidermal water loss (TEWL) is an important no ninvasive method in order to assess the barrier function of the stratu m corneum. As a consequence, TEWL has been found to be a very useful t echnique for studying skin irritation induced by various physical and chemical effects. Exposure of the skin to chemicals (detergents) and p hysical conditions (occlusion and stripping) generally results in an i ncrease of TEWL. Until recently the only commercially available TEWL i nstrument was the Evaporimeter(R) developed by ServoMed (Sweden). The instrument is based on the open chamber system with two humidity and t emperature sensors which measure the water evaporation gradient at the surface of the skin. Recently a new commercially available instrument based on the same physical principle of measurement was developed by Courage and Khazaka (Tewameter(R), FRG). Our aim in this study has bee n to compare the measuring capacities of both instruments. The accurac y, sensitivity, variability and reproducibility of both instruments we re compared in vivo under identical conditions on normal skin and skin damaged by external conditions. The influence of external and environ mental factors such as air and probe temperature, relative humidity, a ir turbulence and pressure of application was evaluated for both instr uments. Finally, the two instruments were compared in practice when fo llowing the increase in TEWL of the skin after stripping, occlusion an d exposure to irritant household detergents. A very good correlation ( r = +0.97) was found between the results of the two instruments over a wide range of TEWL values.