ABSTRACT. The correlation between skin barrier function and transepidermal water loss (TEWL) was evaluated in dogs. Stratum corneum (SC) of 10 healthy dogs was removed by tape stripping (TS), which decreased the corneal layer to allow for permeation of fluorescent dye into skin. TEWL of damaged skin was measured with the closed-chamber-type TEWL analyzer, CC-01. The frequency of TS was directly related to the decrease of SC and the increased permeation of fluorescent dye, and TEWL increased with increasing impairment of skin barrier function. The results suggest that increased TEWL reflects impaired canine skin barrier function. KEY WORDS: canine skin, skin barrier function, transepidermal water loss.J. Vet. Med. Sci. 70(8): 841-843, 2008 The skin functions as an interactive wall of mammalian body, controlling egress of water and suppressing ingress of environmental and microbial agents, thereby preventing skin diseases [3]. Therefore, the maintenance of skin barrier function is critical for the treatment of skin diseases in mammals.Transepidermal water loss (TEWL) is defined as the volume of water that passes from inside to outside of the body through the epidermal layer. TEWL measurement has been used to evaluate skin barrier function in human [1,5,8], and an increase in TEWL has been reported to reflect impairment of skin barrier function [2], i.e., high TEWL suggests low skin barrier function. In addition, in human, a number of studies have suggested that high TEWL is associated in various skin diseases, including atopic dermatitis, psoriasis, contact dermatitis, and ichthyosis [4,10,11,14]. Thus, TEWL is thought to be a useful parameter that characterizes skin barrier function in human.Many skin disorders are suggested to be associated with skin barrier function in dogs [7]. However, the relationship between skin disease and the barrier function is not well analyzed because of paucity of studies on the TEWL value in normal and damaged canine skin. In this study, we evaluated whether TEWL could reflect impaired canine skin barrier function or not.Ten healthy dogs (8 crossbred dogs and 2 beagles, age range 7-13 years, 1 female, 3 sterilized females, and 4 neutered males) were enrolled in this study. All animals were fed on the same food and kept in an air-conditioned room. Two different anatomical areas, lumbar skin and inguinal skin, were used for TEWL measurement. Hair on both areas of each dog was clipped before measurement. Measurements were performed at 23-25°C and 45-65% relative humidity. All dogs were acclimated at least 30 min to the measurement conditions. All experiments were performed in accordance with the guidelines of animal research committee in Tokyo University of Agriculture and Technology.Tape stripping (TS) is a well-known method to artificially damage the stratum corneum (SC) [9,12]. TS was performed on the left and right sides of lumbar skin and inguinal skin of five of ten dogs, using adhesive cellophane tape (Nichiban, Tokyo, Japan). The tape-stripped areas were divided into five pa...