Background/aims: The hydration state of stratum corneum can be measured with different instruments. In the present study, five instruments were compared under different experimental in vitro conditions: Corneometer CM 820 and CM 825, Skicon 200, Nova DPM and DermaLab. Methods: A sorption‐desorption test, measurements on different filters and with liquids with different dielectric constants, measurement‐depth analysis and measurements on different agar plates were performed. Results: Good correlation between the values of the five instruments and μl (sorption test: varying from r= 0.8249 to r= 0.9635) and time (desorption test: correlation varying from r= 0.7615 to r=0.9909) could be demonstrated. A high Spearman correlation coefficient (r) could be proven for dielectric constant (dc)/CM 820 (r=0.9333), dc/CM 825 (r=0.9833) and dc/Nova DPM (r=0.9048). A lower correlation or no correlation was found for dc/DermaLab (r=0.8469; P=0.023) and dc/Skicon 200 (r=0.9000; P=0.083). Conclusions: For each of the five instruments, the electrical field of measurement can be assumed to cover the following depths: CM 820, between 30 and 45 μm; CM 825, around or less than 15 μm; Skicon 200, less than 15 μm; Nova DPM, between 45 and 60 μm; DermaLab, around or less than 15 nm.

Different irritation patterns need different measurement modalities in order to give optimal discrimination over time.

Background/aims: The hydration state of stratum corneum can be measured with different instruments. In the present study, five instruments were compared under different experimental in vivo conditions: Corneometer CM 820 and CM 825 (both capacitance based), Skicon 200 (conductance), Nova DPM (impedance based capacitance) and DermaLab (capacitance). Methods: Seven anatomical sites were tested, a sorption‐de‐sorption test (SDT) and a moisture accumulation test (MAT) were performed. Different hydration states were created on the volar forearms by occluded application of an oil‐in‐water (o/w) emulsion, glycerol and urea containing oil‐in‐water (o/w) emulsion, an untreated control site and a site after lipid extraction with acetone. Measurements were performed 15 min after removal of occlusion. Results: The coefficient of variation for CM 820 ranged between 9.3% and 23.7%; for CM 825 between 14.9% and 36.8%; for Skicon 200 between 53.0% and 167.3%; for Nova DPM between 36.4% and 95.8%; for DermaLab between 23.6% and 45.6%. All devices showed a highly significant correlation (P<0.0001) with a high Spearman coefficient r ranging between 0.7928 and 0.9358. Conclusions: CM 820 and CM 825 seem to differentiate more precisely than Nova DPM, Skicon 200 and DermaLab in dry conditions according to previous findings, i.e., that conductance measurements might be more sensitive for hydrated skin and capacitance measurements might be more sensitive for dry skin conditions. The CM 825, the Skicon 200 and the Nova DPM are suitable for dynamic measurements of hydration parameters of the stratum corneum.

Purpose of the Study: We aimed to evaluate whether prolonged occlusion can induce stratum corneum barrier damage, alterations in stratum corneum hydration or water-holding capacity (WHC) lasting longer than the occlusion time. Materials and Methods: 12 subjects were occluded on the forearm for 24, 48, 72 and 96 h. Two hours after occlusion removal, transepidermal water loss (TEWL) and skin hydration were measured and a sorption-desorption test performed. Results: TEWL showed an increase reaching a plateau on day 2. Hydration and WHC did not show significant changes. Hygroscopicity showed the highest level on day 1, decreasing during the following days. A highly significant correlation between capacitance values and the WHC could be detected (p < 0.0001, r = 0.8206). No correlation could be detected between hygroscopicity and TEWL. Conclusions: Prolonged occlusion induces barrier damage without skin dryness. Occlusion also induces an increased hygroscopicity. A correlation between these two findings could not be proven.

Two studies were performed to evaluate the influence of glycerol on the recovery of damaged stratum corneum barrier function. Measurements of transepidermal water loss and capacitance were conducted in a 3-day follow-up after tape stripping (study 1) and a 7-day follow-up after a barrier damage due to a repeated washing with sodium lauryl sulphate. In study 1 a faster barrier repair (transepidermal water loss) was monitored in glycerol-treated sites. Significant differences between glycerol open vs. untreated and glycerol occluded vs. untreated were observed at day 3. Stratum corneum hydration showed significantly higher values in the sites treated with glycerol+occlusion, compared with all other sites. In study 2 a faster barrier repair was seen in glycerol-treated sites, with significant differences against untreated and base-treated sites 7 days after the end of the treatment. Stratum corneum hydration showed highest values in the glycerol treated sites after 3 days of treatment. Glycerol creates a stimulus for barrier repair and improves the stratum corneum hydration; stratum corneum hydration is not strictly related to barrier homeostasis and can be optimized by different mechanisms and pathways. The observed effects were based on the modulation of barrier repair and were not biased by the humectant effect of glycerol. As the glycerol-induced recovery of barrier function and stratum corneum hydration were observed even 7 days after the end of treatment, glycerol can be regarded as a barrier stabilizing and moisturizing compound.

The differences between pre- and postmenopausal women and men on corneocyte surface area were investigated by a noninvasive exfoliation method. Surface corneocytes were collected with a modified detergent scrub technique. Separated corneocytes were analyzed by videomicroscopy and image analyses (NIH Image^TM 1.59). Additionally transepidermal water loss (TEWL) and stratum corneum hydration, water-holding capacity and moisture accumulation velocity were measured. 21 postmenopausal females without hormonal substitution (age 50.6 years), 33 premenopausal women (age 41.0 years) and 25 men matched for age (age 44.0 years) were included in this study. The smallest corneocyte surface area was seen in premenopausal women (368.0 pixels). For postmenopausal women and the male control population almost equal values could be detected (postmenopausal women 401.1 pixels; men 401.8 pixels). Significant differences were calculated with the ANOVA test (p = 0.0050) and post-hoc analyses (Dunn test); premenopausal vs. postmenopausal women (p < 0.05) and premenopausal women vs. men (p < 0.05), but not postmenopausal women vs. men (p > 0.05). No statistically significant differences could be detected for TEWL, stratum corneum hydration parameters. No correlation could be found between the corneocyte surface area and barrier or hydration parameters. The detected differences support the hypothesis that sexual hormones have an impact on corneocyte surface area, because sex hormone levels are higher in premenopausal women than in non-hormone-substituted postmenopausal women or men.