Objective To evaluate the diagnostic significance oftransepidermal 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/m,Zh 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 m the diagnosis of subclinical irritant contact dermatitis, and their diagnostic value varies with the pattern of irritation.