title: Relationship between transepidermal water loss and temperature of the measuring probe.
abstract: OBJECTIVE
  Transepidermal water loss (TEWL) is an important parameter for the determination of skin barrier function. The open chamber method has been established as the technique of choice in most dermatological laboratories for measurements of TEWL. However, the influence of the probe temperature on TEWL measurements has been the subject of recent controversial debates. In this study the relationship between TEWL measured with the Tewameter and temperature of the measuring probe was therefore investigated by comparing two different measuring techniques.
  
  
  METHODS
  For one measurement, the probe was kept at room temperature (20°C) and for the other one, the probe was preheated to the actual temperature of the measuring object before obtaining the values. Measurements were performed on evaporative standards (EvSs) and healthy individuals. For the EvSs, semipermeable membranes were pulled over a petri dish filled with water, which could be heated.
  
  
  RESULTS
  TEWL values were found to depend on the temperature of the probe. TEWL values were higher when measured with the preheated probe. However, long-term measurements revealed that TEWL values measured with the unheated probe reached those higher TEWL values after approximately 8 min measuring time.
  
  
  CONCLUSIONS
  The final TEWL value was reached after shorter intervals for the preheated probe compared to the unheated probe (2.5 min vs. 4 min) for some measurements. However, preheating of the probe resulted in greater variability of the measurement values. Therefore, measurements with a preheated Tewameter probe is not be recommended.
authors.affiliation: Department of Dermatology, Medical University of Lübeck andproDERM Institute for Applied Dermatology Research, Schenefeld, Hamburg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Thoma
authors.affiliation: Department of Dermatology, Medical University of Lübeck andproDERM Institute for Applied Dermatology Research, Schenefeld, Hamburg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Welzel
authors.affiliation: Department of Dermatology, Medical University of Lübeck andproDERM Institute for Applied Dermatology Research, Schenefeld, Hamburg, Germany.
authors.forename: K P
authors.initials: KP
authors.lastname: Wilhelm
keywords: Tewameter; measuring probe; temperature; transepidermal water loss