Abstract:

Objective To evaluate the diagnostic significance of transepidermal water loss （TEWL）, skin capacitance （CAP） and skin surface pH in subclinical irritant dermatitis. Methods Thirty healthy females took part in the 8-day study. Four areas were delineated on the flexor side of both forearms of each subject: one area received no irritation and served as the control, one was challenged by 1% sodium lauryl sulphate （SLS）, one by repeated tape stripping, and one by irradiation with 0.75 MED UVB. Irritations were continuously given for 5 days. Clinical evaluation was performed everyday before irritation. TEWL, CAP and skin surface pH were measured at baseline, on day 6, 7 and 8 after the first irritation. Results Clinical score maintained at 0 for all subjects through the 8-day study. After SLS irritation, TEWL was 3.17 ± 3.07 g/m2h on day 6, 3.32 ± 2.84 g/m2h on day 7 and 3.22 ± 2.36 g/m2h on day 8, and all were significantly higher than that on day 0 （0.40 ± 1.35 g/m2h, P < 0.01）. Similarly, increased skin surface pH was observed on day 6, 7 and 8 after SLS irritation compared with that at baseline （all P < 0.05）. On the contrast, CAP decreased on day 6, 7 and 8 after SLS irritation （all P < 0.05）. After tape-stripping, a significant increase was observed in TEWL on day 6, 7 and 8 compared with that at baseline （2.54 ± 1.85 g/m2h, 2.40 ± 2.16 g/m2h and 2.17 ± 1.99 g/m2h vs 0.11 ± 1.10 g/m2h, all P < 0.01）; significant increase of pH was noted only on day 8; meanwhile, there was no any significant change in CAP. UVB irradiation induced no obvious changes in any of these physiological parameters. Conclusions These three physiological parameters can be applied to the diagnosis of subclinical irritant contact dermatitis, and their diagnostic value varies with the pattern of irritation.