Reliable use of the ServoMed Evaporimeter EP-2 to assess transepidermal water loss in the canine.

Transepidermal water loss (TEWL) describes the total amount of water lost through the skin, a loss that occurs constantly by passive diffusion through the epidermis. Although TEWL is a normal physiological phenomenon, if it rises too high, the skin can become dehydrated, disrupting form and function and potentially leading to infection or transepidermal passage of deleterious agents. We have validated the use of the Evaporimeter EP-2 for the accurate assessment of TEWL in the canine. We have identified a requirement for the subject to be completely still during measurements, a requirement that can be fulfilled by training. It was found that, following training of the subject, the mean TEWL value dropped, on average, 47% compared to that of untrained animals. A significant effect on TEWL of shaving the coat from the area to be measured was identified. Using the refined protocol we observed that TEWL tended to be higher in adult (2-7 y) than senior (8-11 y) dogs, suggesting that aging processes may be occurring in canine skin that impact barrier function. The implications of poorer barrier function with age could be increased susceptibility to certain skin conditions. The overall poorer skin and coat condition seen for many older dogs may also be related to an increased TEWL.