A comparison of techniques for the measurement of transepidermal water loss

Abstract

An Evaporimeter and a ventilated chamber technique have been compared in their ability to measure transepidermal water loss (TEWL) through rat skin. These techniques measure TEWL under very different conditions; the Evaporimeter measures the net TEWL under ambient relative humidity (RH) whereas the ventilated chamber employs a constant atmosphere, usually of low RH and thus measured the uni-directional diffusion of water. Paired Evaporimeter and ventilated chamber measurements were made of TEWL through normal skin and through skin whose barrier properties had been altered by tape-stripping (15 applications) or single applications of n-hexadecane (28.4 mumol cm-2). Both measuring techniques indicated the same level of TEWL through normal skin (mean 0.3 mg cm-2 h-1) and during increases in TEWL induced by n-hexadecane (max TEWL c 3.5 mg cm-2 h-1). However, the Evaporimeter was found to underestimate the higher rates of TEWL induced by tape-stripping, ie above TEWL raters of 7.5 mg cm-2 h-1. The Evaporimeter is portable, easy to use and suitable for measurements of net water loss up to 7.5 mg cm-2 h-1; it can only be used for comparative assessment of epidermal barrier function if used at a particular ambient RH. The more cumbersome ventilated chamber is to be preferred for accurate assessments of barrier function where high rates of TEWL occur.

A new approach for an estimation of the equilibrium stratum corneum water content

“…The baseline TEWL data are listed in Table 1, and the baseline transport of water across the SC is seen to have relatively stable values, despite the fact that the RH is altered from one day to the other. The average value of the baseline water transport is T b =4.7±0.40 g/hm 2 , which is in the expected range according to the literature (3, 18). The volar equilibrium water content under the TEWL probe is then estimated to be 80±7 μg when the probe area of 1 cm 2 has been accounted for.…”

Water loss through the lip, nail, eyelid skin, scalp skin and axillary skin measured with a closed-chamber evaporation principle

“…The evaporation rates were very high and were of the same order of magnitude as at the palm of the hand. Although the previous open‐chamber evaporimeters have had limitations when measuring high evaporation rates, 9 at low evaporation rates both the open‐chamber principle 10 and the present closed‐chamber principle yielded similar TEWL results for the dorsal forearm. The greatest interindividual variation, 47%, was observed with axillary skin, which may be related to emotional sweating as the measured TEWL value for axillary skin is the sum of passive diffusion and emotional sweating 10 …”

EEMCO Guidance for the Assessment of Transepidermal Water Loss in Cosmetic Sciences

“…However, only a limited number of comparison studies between different types of instruments have been described in the literature [26,27,29,31]. …”

“…In vivo factors, including sodium lauryl sulphate response, skin sites, tape stripping, acetone treatment and other parameters, have also been incorporated in evaluation studies [26,27,[29][30][31].…”