title: 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.
mesh_terms: D000269:Adhesives / Q000494:pharmacology; D000473:Alkanes / Q000494:pharmacology; D000818:Animals; D004058:Diffusion; D005260:Female; D051381:Rats; D011919:Rats, Inbred Strains; D012867:Skin / Q000187:drug effects; D014870:Water Loss, Insensible / Q000187:drug effects
chemical_list: D000269:Adhesives; D000473:Alkanes; C007932:n-hexadecane