Author	Title	No. of subjects	Study population/method	In vivo or in vitro	Device/s	Results: measurement property—measurement error/agreement	Results: measurement property—reliability
Anthonissen et al. 51	Measurement of elasticity and transepidermal water loss rate of burn scars with the DermaLab	32	Thirty‐two active burns scars (grafted and spontaneously healed) and normal skin. Two consecutive measurements for TEWL were taken by a first assessor and one measurement by a second observer. A period of 4 min between all measurements was taken.	In vivo	DermaLab (Cortex Technologies, Hadsund, Denmark)	SEM ≤1.74 for intra‐observer reliability and SEM ≤2.76 for inter‐observer reliability.	Intra‐ and inter‐observer reliability. ICC ≥0.86 for intra‐observer reliability and ICC ≥0.78 for inter‐observer reliability.
Barel and Clarys 55	Study of the stratum corneum barrier function by transepidermal water loss measurements: comparison between two commercial instruments—Evaporimeter and Tewameter	16	Volunteers aged 18–30 years. Various anatomical sites. Conditions: normal, after occlusion or stripping.	In vivo	Evaporimeter 2100 (Servomed AB, Stockholm, Sweden), Tewameter TM210 (Courage and Khazaka, Cologne, Germany)	The range of the CV for the Tewameter varies from 6% to 13% and the Evaporimeter varies from 3% to 6% at different anatomical sites.	Influence of external room temperature, r = 0.88 for Tewameter and r = 0.89 for Evaporimeter, correlates with increase in temperature. There is a significant effect of the pressure of the probe on the skin. Significant air movements have an effect on TEWL measurements but breathing or moving doors has almost no influence. Correlation between TEWL measurements at different skin sites under various conditions, n = 16, r = 0.97.
Blichmann and Serup37	Reproducibility and variability of transepidermal water loss measurement	10	Ten healthy volunteers. Measurements done on palm of the hand and flexor side of forearm. Successive measurements on the same individual over 3 min.	In vivo	Evaporimeter EP1 (Servomed AB)	Intra‐individual reproducibility on palm of hand: CV = 9.4%. Intra‐individual reproducibility on the forearm = 9.1%. Variation of TEWL among different individuals to measurements on the palm and forearm show a CV ranging from 31% to 57%. The variation by time of the group of individuals (over 24 h) was relatively minor.	Intra‐individual reproducibility reported as mean difference as % of initial TEWL measurements on the palm of the hand varied between 6.4% and 14.5% and for the forearm varied between 11.3% and 34.1%.
Cointereau‐Chardon et al. 49	Self‐recording the skin hydration and transepidermal water loss parameters: a pilot study	20	Twenty healthy women recruited through an employment agency. Selected as they had moderately dry skin on cheeks and forearms. Aged 45–60 years. Two successive measurements were self‐recorded and in the lab on two close regions on cheeks and forearm (four sites). Then applied glycerol product. Measured every hour until 6 h and again in the morning. Then after washing and 15 min later.	In vivo	GPSkin Pro (Gpower, Seoul, South Korea)	TEWL arm: mean = 2.96, SD = 4.49. TEWL face: mean = 3.85, SD = 7.06.
De Paepe et al.9	Validation of the Vapometer, a closed unventilated chamber system to assess transepidermal water loss versus the open chamber Tewameter	16	Sixteen healthy females, no skin disease. Evaluation of skin on forearms. Six visits over a 4 weeks period. Measurements: baseline values, reproducibility assessed by conducting 10 consecutive measurements per volunteer, effect of an application of a cosmetic cream and recovery after SLS. Corresponding test zone on other forearm treated with water.	In vivo	Tewameter TM210 (Courage and Khazaka), Vapometer SWL‐2 (Delphin Technologies, Kuopio, Finland)	The variability of the baseline readings for each site was similar for both devices. Values significantly higher (p < 0.001) for the Tewameter than for the Vapometer. Smaller differences in TEWL could be detected with the Tewameter at tape stripping skin. Based on the standard errors of the differences and the mean square error from the analysis of variance, the Tewameter provided more precise results when measuring the effect of a moisturiser. TEWL values obtained with the Vapometer, 10 consecutive measurements for each volunteer. A shift in an upward direction was observed going from 5 ± 3 g/h/m2 (first replicate) to 7 ± 3 g/h/m2 (10th replicate). The variability of each replicate, however, remained the same (Levene's test for equality of variances, p = 0.778). When the higher sets of readings were compared with the first set, a significant difference was found for the fifth and the seventh reading onwards, meaning that reproducible results were only obtained for the first four sets of readings.	Spearman's correlation coefficients were determined, the results retrieved with both devices were correlated (r varying from 0.503 to 0.966).
Elkeeb et al. 30	Correlation of transepidermal water loss with skin barrier properties in vitro: comparison of three evaporimeters		Dermatomed human cadaver skin without obvious signs of skin disease. TEWL measurements were carried out by placing the collared probe over the specially designed top of the donor compartment 1 cm away from the surface of the skin, and was fitted using a surrounding rubber ring. Measurements were conducted at 0 times (before 3 h water dosing) and 1, 2, 4 and 24 h after dosing.	In vitro	Tewameter TM210 (Courage and Khazaka), AquaFlux AF200 (Biox Systems Ltd, London, UK)		The patterns of TEWL profiles from the three instruments were similar. However, the measurement capacity of the AquaFlux is significantly higher than those of Tewameter or Vapometer (value not given, p < 0.001). Baseline TEWL measured with AquaFlux at zero time is correlated with the flux rate of tritiated water (p = 0.04, r 2 = 0.34). Baseline TEWL measured with Tewameter, similar to that of AquaFlux, correlates with the flux of tritiated water (p = 0.00, r 2 = 0.50). Vapometer, however, shows no statistically significant correlation with the flux rate of tritiated water (p = 0.07, r 2 = 0.31).
Farahmand et al.33	Measuring transepidermal water loss : a comparative in vivo study of condenser‐chamber, unventilated chamber and open ‐chamber systems	6	Performed on human forearm skin (n = 6) without skin disorders, in the normal condition (baseline), and after (1) 10 tape strippings on both arms, (2) moisturiser cream (Eucerin Calming Cream) and petrolatum application for 1 h and (3) 1% SLS aqueous solution and distilled water (as control) application for 20 min. All measures performed three times.	In vivo	Tewameter TM210 (Courage and Khazaka), Vapometer SWL‐2 (Delphin Technologies), AquaFlux AF200 (Biox Systems Ltd)	Tewameter CV ranged from 17.3% to 60%. Vapometer CV 11.5%–49.6% AquaFlux CV 4.8%–31.1%	TEWL values measured by three instruments are correlated significantly (p < 0.001). Pearson's correlation coefficient is 0.58 for AquaFlux and Vapometer, 0.70 for Vapometer and Tewameter, and 0.88 for Tewameter and AquaFlux.
Fell et al.52	The Scarbase Duo: intra‐ and inter‐rater reliability and validity of a compact dual scar assessment tool	20	Twenty patients (20 scars) recruited from burns outpatient clinic with active scars. Scars on the upper and lower limbs. Average scar age 5.65 m. Contralateral area of skin used for comparison or neighbouring skin. Two measurements taken by the first rater with Scarbase Duo then measured the same area with the DermaLab. The second rater conducted a single measure with each device.	In vivo	DermaLab (Cortex Technologies), Tewameter (as part of Scarbase Duo: Courage and Khazaka)	Moderate SEM values (0.74–1.17) for Tewameter. The Bland–Altman plots for agreement between the two tools on scars show the bias of the mean is high, suggesting that a systematic error could be detected. The DermaLab systematically measures approximately 2.5 g/m2 higher than the Tewameter. The LoA are far apart, suggesting that the high correlation between the two measurement methods is not supported by high agreement.	Tewameter: intra‐rater reliability (scar), ICC = 0.95, SEM = 1.17, (healthy skin), ICC = 0.87, SEM = 0.74; inter‐rater reliability (scar), ICC = 0.96, SEM = 1.12, (healthy skin), ICC = 0.90, SEM = 0.75. Concurrent validity of TEWL measurements between the Tewameter and the DermaLab—scar: ICC = 0.81, r = 0.93, good to excellent correlation. Healthy skin: ICC = 0.52, r = 0.72, moderate correlation. The DermaLab systematically measures approximately 2.5 g/m2 higher than the Tewameter.
Fluhr et al.7	transepidermal water loss reflects permeability barrier status: validation in human and rodent in vivo and ex vivo models		Ex vivo mouse model: skin removed from mice. In vivo mouse model: lowering of TEWL with petrolatum, increase TEWL by tape stripping 2, 3, 6 and 8×. In vivo human skin: volar forearms, tape stripped skin 10×.	Ex vivo, in vivo	DermaLab (Cortex Technologies), Evaporimeter EP1 (Servomed AB), Tewameter TM210 (Courage and Khazaka), Tewameter TM300 (Courage and Khazaka), Vapometer (Delphin Technologies), H4300 (NIKKISO‐YSI Co, Ltd, Tokyo, Japan), MEECO (MEECO, Warrington, PA, USA)	The CV was highest for the DermaLab (18.0), followed by MEECO (16.6), Vapometer (12.8) (in vivo). The H4300 (12.4), TM210 (12.0), EP1 (13.5) and TM300 (1.9): in vivo study on human ventral forearm.	Correlation with gravimetric values: for EP1 (r = 0.8076) > TM210 (r = 0.7666) > VapoMeter (r = 0.7630) > TM300 (r = 0.7557) > H4300 (r = 0.7082) > MEECO (r = 0.6825). Significant correlation was found between all devices of at least r > 0.83 however the TM210 correlated less well than the other devices (r up to 0.9879). All instruments significantly correlated with each other from the in vivo study on the ventral forearms, however, the MEECO system correlated less well with the H4300 and the TM210.
Gardien et al.21	transepidermal water loss measured with the Tewameter TM300 in burn scars.	53	Fifty‐five (final 53, two excluded due to instrument reading error) patients with burn scars 3, 6 and 12 m after burn. Morphological characteristics measured with POSAS and colour measured with DSM II ColourMeter. Three study areas: scar, adjacent normal skin and contralateral skin. Two observers. Two measures by first observer and one measure by second observer. 94% of observer 1 measurements were one person. Single measurements were performed by two different observers 42% and 58%.	In vivo	Tewameter TM300 (Courage and Khazaka)	Intra‐observer SEM: 2.38–2.68 g/m2/h. Inter‐observer SEM: 1.76–3.97 g/m2/h. Bland–Altman plots showed relatively wide LoA values for scar and healthy skin.	Intra‐observer reliability ICC: 0.89–0.92 (excellent agreement). Inter‐observer reliability ICC: 0.85–0.94 (excellent agreement).
Grinich et al. 45	Validation of a novel smartphone application‐enabled, patient‐operated skin barrier device	50	Fifty participants with healthy skin, volar forearms. Participants collected their own measurements with GPSkin with minimal instruction. AquaFlux measurements were taken by the investigator. Because of the low test‐‐retest reliability in the first trial, methods were modified to include increased participant education on device use prior to the start of trial 2.	In vivo	GPSkin Pro (Gpower), AquaFlux AF200 (Biox Systems Ltd)		In trial 1, GPSkin demonstrated ‘poor’ test‐‐retest reliability (ICC = 0.18, 95% CI: −0.08 to 0.42) for TEWL, whereas the AquaFlux showed ‘moderate’ reliability (ICC = 0.58, 95% CI: 0.36‐‐0.73) for TEWL. In trial 2, test‐‐retest reliability of GPSkin TEWL measurements improved to ‘good’ for participant (ICC = 0.89, 95% CI: 0.82‐‐0.94), investigator (ICC = 0.88, 95% CI: 0.79‐‐0.93) and participant‐‐investigator (ICC = 0.88, 95% CI: 0.79‐‐0.93) comparisons. The AquaFlux also demonstrated ‘good’ reliability for TEWL (ICC = 0.86, 95% CI: 0.76‐‐0.92). The devices were moderately correlated by Spearman's for TEWL (r 2 = 0.48, p = 0.0004) when AquaFlux versus participant taken measures with GPSkin. Participant GPSkin after education TEWL measurements and the AquaFlux were moderately correlated (rs = 0.40, p = 0.0045) while investigator GPSkin TEWL measurements and the AquaFlux were weakly correlated (rs = 0.34, p = 0.0147).
Grinich et al.46	Validation of a novel patient‐operated device for measuring skin barrier function in atopic dermatitis	50	Fifty 18+ years of AD patients with varying disease severity performed self‐measurements at volar forearm with GPSkin, while investigators collected data, two measurements with each, with all three devices, on both non‐lesional and lesional skin.	In vivo	GPSkin Pro (Gpower), AquaFlux AF200 (Biox Systems Ltd)	GPSkin demonstrated poor agreement with standard devices in Bland–Altman plots. GPSkin consistently measured lower mean values for TEWL compared to the AquaFlux as indicated by the positive bias line (mean difference between measurements from GPSkin and the standard device). The discrepancy in GPSkin and standard devices was most significant at higher TEWL values.	GPSkin versus AquaFlux demonstrated strong correlation for patient measured: r 2 (non‐lesional) = 0.72, r 2 (lesional) = 0.68 and clinician measured r 2 (non‐lesional) = 0.80, r 2 (lesional) = 0.66. Test–retest reliability ICC values for GPSkin ranged from 0.67 to 0.90 (CIs provided in the study). The AquaFlux ICC value was 0.90 (0.84–0.94) for non‐lesional skin and 0.76 (0.61–0.86) for lesional skin.
Grove et al.38	Comparative metrology of the Evaporimeter and the DermaLab transepidermal water loss probe	11	In vitro: foam fully loaded with standard amount of water placed under probes simultaneously under different polymeric films with different WVTR. A series of measurements in which the evaporative water loss was sequentially determined on the low, medium and high WVTR films 10 times in succession was performed using a fixed duration program that calculated the mean water loss rate. In vivo: 11 panellists had volar forearms exposed to 5% aqueous solutions of eight test products under occlusion for 24 h. TEWL rates measured in duplicate by Evaporimeter and DermaLab.	In vitro and in vivo	DermaLab (Cortex Technologies), Evaporimeter EP1 (Servomed AB)	The CV was higher for the Servo Med evaporimeter (6.2%–46.8%) than the DermaLab (4.3%–20.7%), which means the reproducibility was better with the DermaLab (in vitro).	There was excellent agreement between the Servo Med evaporimeter and the DermaLab TEWL probe (R 2 = 0.9589). The DermaLab values tended to be less than the corresponding value obtained with the Servo Med evaporimeter. There was excellent agreement between the Servo Med evaporimeter and the DermaLab in vivo (R 2 = 0.8665).
Hon et al.22	Are skin equipment for assessing childhood eczema any good?	80	Subjects with AD, aged 1–18 years, measurements at 2 cm below elbow, volar forearm. Eighty sets of clinical scores.	In vivo	Tewameter TM300 (Courage and Khazaka), Vapometer (Delphin Technologies)		There are significant correlations between measurement by the two devices of TEWL (r = 0.357, p < 0.05). However, it seems that Vapometer performs better than TM300 in general with regards to comparison to other clinical measures.
Hua et al. 23	Comparison of two series of non‐invasive instruments used for the skin physiological properties measurements: the DermaLab from Cortex Technology versus the series of detectors from Courage and Khazaka	30	Thirty healthy volunteers, areas on the face measured. Randomly assigned to Group A or B where instruments were swapped with regards to which side they measured. Also measured on mid forearm. Three measurements on each side.	In vivo	DermaLab (Cortex Technologies), Tewameter TM300 (Courage and Khazaka)	DermaLab TEWL probe CV% minimum–maximum 0.00–20.75, mean = 6.35, SD = 3.92. TM300 CV% 0.86–17.70, mean = 6.08, SD = 3.57.	DermaLab versus TM300 r = 0.940, p < 0.001
Imhof et al. 31	Rapid measurement of transepidermal water loss with a condenser‐chamber instrument	1	A condenser‐chamber device (AquaFlux) was compared to a traditional open chamber device (Vapometer). In vivo studies used 12 measurements from seven sites (wrist to forearm) with both devices. In vitro study used 200 repeat measurements from each device.	In vivo and in vitro	Vapometer (Delphin Technologies), AquaFlux AF200 (Biox Systems Ltd)	For AquaFlux TEWL measurements in vivo SD varied between 0.81 g/m2/h, CV = 6.4% at wrist and SD 0.16 g/m/h, CV = 2.0% in middle of forearm. Compared to SD 0.09 g/m/h and CV 1.2% in vitro. For the Vapometer results from 200 measurements using an in vitro source had an average of 9.02 g/m2/h and a CV of 10.3%. The Vapometer in vivo source CV varied from 8.2% to 12.3%.	There is broad agreement between the VapoMeter and AquaFlux measurements, characterised by a Pearson correlation coefficient of R = 0.82 (in vivo).
Kikuchi et al. 24	Comparison of the measuring efficacy of transepidermal water loss of a reasonably priced, portable closed chamber system device H4500 with that of rather expensive, conventional devices such as Tewameter and Vapometer	15	Ten healthy volunteers. Measurements conducted by the same investigator, repeated 10 times on volar forearm (Study 1). Study 2: 15 healthy volunteers, forearms, taped stripped on the right and 0.5% SLS applied for 24 h under occlusion on the left.	In vivo	Tewameter TM300 (Courage and Khazaka), Vapometer SWL‐2 (Delphin Technologies), H4500 (Nikkiso‐Therm Co Ltd, Musashino, Japan)		Intra‐rater reliability: ICC with 95% CI of H4500, Vapometer and Tewameter were 0.927 (0.835–0.978), 0.856 (0.697–0.955) and 0.93 (0.842–0.979), respectively. All measured sites: H4500 versus Tewameter r = 0.945, H4500 versus Vapometer r = 0.910, Vapometer versus Tewameter r = 0.939 (all p < 0.001). Healthy skin: H4500 versus Tewameter r = 0.756, H4500 versus Vapometer r = 0.431, Vapometer versus Tewameter r = 0.492. Immediately after tape stripping: H4500 versus Tewameter r = 0.718, H4500 versus Vapometer r = 0.900, Vapometer versus Tewameter r = 0.850. 24 h after tape stripping: H4500 versus Tewameter r = 0.811, H4500 versus Vapometer r = 0.843, Vapometer versus Tewameter r = 0.861. After 24 h of SLS: H4500 versus Tewameter r = 0.768, H4500 versus Vapometer r = 0.849, Vapometer versus Tewameter r = 0.533.
Lau‐Gillard et al. 36	Evaluation of a hand held evaporimeter (VapoMeter) for the measurement of transepidermal water loss in healthy dogs	23	One human volunteer and 22 dogs. All healthy without skin conditions. Measurements carried out by a single operator in non‐climate controlled room but stable conditions. Human participant uncovered skin immediately before readings. TEWL measured 10× at four different body sites on human. Upright and upside‐down. Repeated measurements 4 days later. In dogs: 10 readings on unclipped skin and 2 min after clipping. Ten consecutive readings obtained at 12 body sites on 5 different days (non‐consecutive) in both the short‐coated dog and the long‐coated dog. To compare TEWL in a larger group of dogs, 10 consecutive readings obtained from the right and left lateral thorax in the additional 20 dogs.	In vivo	Vapometer SWL‐5 (Delphin Technologies)	For the short‐coated dog, CVs for readings obtained at various sites on various days ranged from 7.3% to 76.9% with a mean of 33.4% (95% CIs ranged from 29.5% to 37.2%). Long‐coated dog, CVs ranged from 4.7% to 43% with a mean of 20.3% (95% CIs ranged from 18% to 22.7%). CVs were significantly lower in both axillae compared to the top of head and between shoulders, and on the right leg compared to between shoulders (Tukey's multiple comparison, p < 0.05).
Logger et al. 47	Value of GPSkin for the measurement of skin barrier impairment and for monitoring of rosacea treatment in daily practice	43	Pilot 1: 27 healthy participants. GPSkin compared with AquaFlux at the forearm before and after tape stripping and at both cheeks without intervention. Pilot 2: 16 rosacea patients, GPSkin measurements at the forearm and both cheeks before and during anti‐inflammatory treatment, values compared to pilot 1 values.	In vivo	AquaFlux AF200 (Biox Systems Ltd)		Pilot 1: GPSkin versus AquaFlux: linear regression R = 0.8718, p < 0.0001, Spearman correlation coefficient R = 0.9256, p < 0.0001
Miteva et al. 25	Approaches for optimising the calibration standard of Tewameter TM300		Under laboratory conditions consecutive measurements taken with five different probes on three different membrane surfaces.	In vitro	Tewameter TM300 (Courage and Khazaka)	The results obtained by measuring with five different probes on three different types of models (i.e. a heated petri dish, an unheated petri dish and a calibration bottle) revealed some variation. SDs varied from 1% to 6% for the heated petri dish and 2%–9% for the unheated petri dish. The SD for the measurements completed on the calibration bottle reached a maximal of 0.4%.
Murphrey et al. 48	Can a hand held device accurately measure barrier function in ichthyoses?	30	Thirty ichthyosis subjects and 25 age and sex matched controls. Three serial TEWL readings taken at non‐overlapping locations on the volar arm. Taken on 2 successive days.	In vivo	GPSkin Barrier Light (Gpower), AquaFlux AF200 (Biox Systems Ltd)	Bland–Altman analysis was performed to assess agreement between AquaFlux and GPSkin, which was worse at higher TEWL values for GPSkin.	In the combined cohort, both devices showed excellent test–retest reliability, with ICC = 0.984 (95% CI, 0.973–0.991) for AquaFlux and ICC = 0.974 (95% CI, 0.959–0.984) for GPSkin. When the population was analysed after sub‐dividing into ichthyosis and controls, the ICCs remained excellent for subjects with ichthyosis (AquaFlux ICC = 0.976 (95% CI, 0.954–0.988), GPSkin ICC = 0.974 (95% CI, 0.953–0.987)), and was good for controls (AquaFlux ICC = 0.816 (95% CI, 0.646–0.912), GPSkin ICC = 0.868 (95% CI, 0.745–0.937)). Readings from the two instruments were strongly positively correlated for the entire cohort (rs = 0.743, p < 0.001) and moderately well correlated when analysed separately for ichthyosis (rs = 0.518, p = 0.003) and controls (rs = 0.536, p = 0.006). When the entire population was divided at the median of GPSkin measurements, the correlation between GPSkin and AquaFlux was better at the higher range (above the median, 9.7 g/m2/h; rs = 0.675, p < 0.001) than below the median (rs = 0.499, p = 0.008), although correlation was still moderate to strong with both devices.
Norlén et al. 56	A new computer‐based evaporimeter systemic for rapid and precise measurements of water diffusion through stratum corneum in vitro	36	A new computer‐based evaporimeter was used to measure water uptake, water diffusion rate under controlled conditions in vitro stratum corneum samples from 36 patients who had breast reduction. Measurements were taken over 10 000 s to achieve equilibrium. The system was used on a free water surface, with 20 runs to gain reference data. Water diffusion data were calculated 10 times (once every 3 days) in vitro on one SC piece. This was compared to 10 measurements of one patient from mid forearm.	In vitro	Author fabricated evaporimeter, Evaporimeter 2100 (Servomed AB)	The precision of the water diffusion rate measurements through mounted SC samples was 11% (TEWL being 1.9 ± 0.1 g/m2/h (95% CI of mean; n = 10)), the corresponding value for the TEWL measurements in vivo on human left forearm was 36% (TEWL being 8.7 ± 1.9 g/m2/h (95% CI of mean; n = 10).
Nuutinen et al. 32	A closed unventilated chamber for the measurement of transepidermal water loss.	10	Water‐filled petri dish with a semi‐permeable membrane heated to 80°C then allowed to cool. Measurements taken during cooling process. Dish weighed with a scale simultaneously. Ten health volunteers had TEWL measurements repeated 10 times on volar forearm and palm of the hand.	In vitro and in vivo	Vapometer (Delphin Technologies)	For the Vapometer only: the CV was 8.0% for the forearm, 10.1% for the palm of the hand and 4.0% for the petri dish.	Evaporation rate from a petri dish was correlated with the Vapometer and DermaLab measurements. Evaporation rate of Vapometer was r = 0.99, p < 0.001 until the evaporation was 200 g/m2/h from the petri dish. For the DermaLab up to 120 g/m2/h, r = 0.99, p < 0.001, after this it underestimates evaporation rates
Park and Tamura 39	Measurement of regional evaporation rate from skin surface by evaporimeter	10	After calibration of two sensors measurements were taken at the thigh with and without a mounted wetted filter paper. Measurements confirmed by weighing the wetted filter paper every 30 min and comparing total weight loss of the person. Assessments also completed at different temperatures. The probe was applied on each skin/wetted paper surface every 5 s for 10 min. Subjects were 10 female students aged 22—34 years.	In vitro and in vivo	Evaporimeter EP1 (Servomed AB)		Correlation between evaporation rate measured and weight loss of filter paper, r = 0.98. Correlation between body weight loss and cutaneous evaporation rate, r = 0.91. Regression formula for body weight loss (y) compared with evaporation rate (x) is y = 2.06 + 2.53x.
Pinnagoda et al. 40	Comparability and reproducibility of the results of water loss measurements: a study of four evaporimeters	1	In vitro: petri dish filled with water and covered with Opsite dressing to form a semi‐permeable membrane. Plastic cover pulled away so probe can begin measuring from 3 mm away for 6 min, 5× per probe. In vivo: TEWL measured on volar aspect of the right forearm of one subject at one location. Recorded continuously for 4 min, 3× measurements per probe.	In vitro and in vivo	Evaporimeter EP1 (Servomed AB)	In vitro: after stabilisation the SDs of the mean for each probe decreased from 0.8 to 0.2 g/m2 h indicating reproducibility of the successive measurements is high. In vivo: until stabilisation was reached the SDs of the mean for each probe decreased from about 0.4 to 0.2 g/m2 h. After stabilisation, they remained below 0.2 g/m2 h.
Rogiers 41	Transepidermal water loss measurements in patch test assessment: the need for standardisation	21	The Tewameter TM200 was compared to the Evaporimeter EP1 in 21 females (22–29). TEWL measurements were measured and compared under various conditions (different probe temperatures, different skin hydration, environmental temperature and patch test with blank and SLS patches).	In vivo	Evaporimeter EP1 (Servomed AB), Tewameter TM200 (Courage and Khazaka)	For blank patch comparison Tewameter had TEWL of 8.1 ± 1.2 left arm and 8.0 ± 1.1 right arm as opposed to EP1 values of 4.6 ± 1 left arm and 4.9 ± 1.1 right arm. No significance was found in difference between sites, but EP1 had significantly lower values (p < 0.001) in both sites. For blank versus SLS patches the values for TM200 were 30.3 ± 11.6 (CV = 38%) versus 8.1 ± 1.4 (CV = 17%), respectively. The respective values for EP1 were 18.9 ± 8.5% (CV = 45%) versus 4.6 ± 1.2 (CV = 26%). The difference in values between blank and SLS was significant between the two groups. The intergroup CV was significantly higher for the EP1. Inter‐group variations (10.8 ±3.5) and intra‐group (20.1 ± 2.7) variability for measurements at different times of the day and on the same day across different weeks were not significant.
Rosado et al. 26	Comparative assessment of the performance of two generations of Tewameter: TM210 and TM300	15	Fifteen healthy volunteers. Measurements taken on the volar forearm. Comparative measurements with the two devices were carried out simultaneously, on opposite sites in each volar forearm. Recorded components: stabilisation time, TEWL, VC% after three TEWL measurements performed every 5 min, VC% in extreme conditions (three measurements every 5 min after the skin was covered with an occlusive patch for 1 h).	In vivo	Tewameter TM210 (Courage and Khazaka), Tewameter TM300 (Courage and Khazaka)	Under normal conditions the VC% was not statistically significantly different (p = 0.27) but the TM210 performed slightly better with an average VC of 6.75. Under extreme conditions the TM300 performed better but was not statistically significantly different (p = 0.310). For t1/2evap (evaporation half‐life) the TM210 provided higher TEWL results and slower decay and was statistically different from the TM300 (p = 0.003). The measurement of dynamic water mass also differed between the two models (p = 0.003).
Scott et al. 42	A comparison of techniques for the measurement of transepidermal water loss	72	Normal and tape stripped rat skin measured first with Evaporimeter then with a purpose built ventilated chamber apparatus. Measurements taken on 72 animals.	In vivo	Evaporimeter EP1 (Servomed AB)	Untreated skin: mean TEWL values was 0.30, SEM ±0.02 and for the unventilated chamber was 0.32, SEM ±0.02. Tape stripped skin (n = 9): evaporimeter mean TEWL 7.41, SEM ±0.16, ventilated chamber 19.04 ±SEM 1.60.
Shah et al. 34	Comparative evaporimetry in man	9	Two Tewameters and one Vapometer used on nine healthy volunteers with normal skin. Three sets of TEWL measurements performed simultaneously with each instrument. Seven sites chosen: three forehead, three volar forearm, and middle of the scalp (Vapometer only).	In vivo	Tewameter TM210 (Courage and Khazaka), Vapometer SWL‐3 (Delphin Technologies)	In all cases the SDs associated with each instrument were small and the CV for all sites clearly indicated that the reproducibility of successive measurements with any individual instrument was high. CV for TM210 ranged from 9.2% to 25%. CV for the Vapometer ranged from 14.9% to 21.2%.	For TEWL values of all forearm locations, there were no statistically significant differences between the mean values measured by all three instruments (p = 0.68–0.90). For TEWL values of forehead locations, there was significant difference between the mean values of both open chamber device and closed chamber device (p = 0.0049–0.04).
Sim et al. 50	Portable skin analysers with simultaneous measurements of transepidermal water loss, skin conductance and skin hardness		Device (THC) calibrated using a wet‐cup method: water‐filled petri dish is covered with a semi‐permeable membrane, controlled for temperature of the water. Evaluated in terms of sensitivity and linearity from the measured calibration curve. Compared against the GPSkin.	In vitro	GPSkin Pro (Gpower), THC	THC sensitivity of 0.0068 (%/s)/(g/m2/h) with the high linearity of 99.63%. Coefficient of determination shows 0.8613, indicating a good agreement of a linear relation between two devices.
Smallwood and Thomas57	An inexpensive portable monitor for measuring evaporative water loss	2	Device is calibrated first with three different saturated salt solutions. Then used to test water loss rates from two subjects with C5/6 spinal lesions at seven different locations.	In vitro	Author fabricated evaporimeter	The monitor can measure evaporative water loss at normal rates of 10–20 g/m/h to an accuracy of about 10% of the reading.
Steiner et al. 27	Side‐by‐side comparison of an open chamber (TM300) and a closed chamber (Vapometer) transepidermal water loss meter	17	Compared the results of TEWL measurements between two commonly used open and closed chamber TEWL devices. Five hundred and forty measurements were taken in 17 participants on the dorsum and palm of both hands on 2 days and the order of the devices was randomised. The TM300 was used in two modes: once as the standard open chamber model and second as a closed chamber model using the supplied semi‐permeable ring.	In vivo	Tewameter TM300 (Courage and Khazaka), Vapometer (Delphin Technologies)	The mean difference for open (TM300) minus closed method is 1.3 g/m2 h, with agreement limits of ‐5.4 and 8.2 g/m2 h. The agreement is very good for the range up to 20 g/m2 h. The measurements outside the agreement limit are predominantly for higher TEWL measurements. Comparing the Vapometer against the TM300 open chamber, the mean difference is 1.2 g/m2 h but the agreement limits are within the range of ‐35.8 and 38.3 g/m2 h difference. Both devices yield similar measurements in the range up to about 25 g/m2 h, and above an average of about 55 g/m2 h the TM300 records systematically lower readings compared with the Vapometer; this effect increases with increasing TEWL readings.	The intra‐class correlation coefficient (ICC) comparing the TM300 open chamber TEWL with the closed chamber version is 0.98 (95% CI: 0.97–0.98) and 0.70 (95% CI: 0.65–0.74) for the Vapometer.
Tagami et al.53	A portable device using a closed chamber system for measuring transepidermal water loss: comparison with the conventional method	21	Compared TEWL measurements between the H4300 and DermaLab evaporimeters in 21 healthy volunteers, four atopic dermatitis, three psoriatic patients aged 22—81 years. For healthy patients measurements were from cheek, flexor surface of forearm, extensor surface of leg. For patients with skin lesions measurements were taken from various lesions on the extremities. Measurements were at 50% humidity and 21°C.	In vivo	DermaLab (Cortex Technologies), H4300 (NIKKISO‐YSI Co, Ltd)	H4300 had variation of ∼15% when measured across different anatomical sites (higher on cheek than other areas). DermaLab 12.0 ± 1.0 cheek, 4.7 ± 0.5 forearm, 5.6 ± 0.7 leg (p < 0.0001). DermaLab CV 8.33, 10.64, 12.5%. Similar differences in closed chamber device: cheek (6.7 ± 0.6), forearm (2.3 ± 0.2), leg (2.8 ± 0.4) (p < 0.0001). Similarly results from patients with atopic dermatitis or psoriasis were higher than those from normal patients in both devices.	When all the data were compared, the TEWL values obtained with the closed system device correlated well with those obtained with the open system device, the DermaLab. An excellent linear relationship (R 2 = 0.92; p = 0.0001) was found, over a wide range of TEWL values, between the two different instruments
Van Sam et al.43	Transepidermal water loss management standardisation: kinetic and topographic aspects	34	TEWL measurements by the EP1C evaporimeter in 11 patients (aged 22—55 years) on three different sites (wrist, mid forearm, elbow). In the second set of experiments measurements were taken from seven patients from site 2 at 5 min intervals, for 2 h on 3 consecutive days to study reproducibility. Then measurements were taken from 16 patients on one day measured with the same intervals.	In vivo	Evaporimeter EP1 (Servomed AB)		ANOVA test showed no influence of subjects on variability in results and that inter‐subject reproducibility was good, and reproducibility was the same for the anatomical sties (p = 0.05). Hartley test showed that for each time, all patient values were the same and reproducibility was good.
Yamamura et al.44	Simple monochromatic refractometer for transepidermal water loss	44	Forty‐four patients (21 males, 23 females, mean age 42.61 years) with normal skin and 12 patients with various skin conditions. TEWL measurements from frontal surface of the lower leg at the same time by both devices.	In vivo	Noevir‐EVA, Evaporimeter EP1 (Servomed AB)		There was agreement between the Noevir‐EVA device and the commercially available Evaporimeter EP1 r = 0.984
Ye et al.28	Validation of GPSkin Barrier for assessing epidermal permeability barrier function and stratum corneum hydration in humans	200	Measurements in 200 patients (74 males, 126 females) aged 1–78 years. All patients had no soap, or detergent for 12 h and no skin care products for 24 h. All measurements were performed by Ye et al. TEWL and SC hydration were measured on the cheek, the dorsal hand, and the forearm (flexor site) with TM300 and Corneometer CM825, respectively, attached to a Courage and Khazaka MPA5 system. Readings were taken with a laptop connected to MPA5. When using GPSkin Barrier, perpendicularly placing the device on the measurement site for 10 s, both TEWL and SC hydration readings are shown on a smartphone.	In vivo	Tewameter TM300 (Courage and Khazaka), GPSkin Barrier Light (Gpower)	In the cheek TM300 mean ± SEM was (19.08 ± 0.77) and GPSkin (12.34 ± 0.65). Forearm: TM300 (17.8 ± 0.73) and GPSkin (10.87 ± 0.54). Dorsal hand: TM300 was (21.57 ± 0.8) and GPSkin was (14.96 ± 0.61).	Cheek r = 0.7009, p < 0.0001. In the forearm, r 2 = 0.6449, p < 0.0001. In the dorsal hand, R 2 = 0.6991, p < 0.0001.
Yoshihara et al.29	A new method of measuring the transepidermal water loss of dog skin	21	Study conducted on 19 beagles (11 males, 8 females, 1–5 years old) and two cross‐bred dogs (7 years old females). CC01 was compared to T300. TEWL measurements were also taken across different anatomical sites, different relative humidity's (58%, 78%) and different temperatures (18°C, 20°C, 22°C, 24°C, 26°C, 28°C). Hair was clipped on four different sites (lumbar back, shoulder, leg, tail base) were measure at each site five times with each device.	In vivo in dogs	Tewameter TM300 (Courage and Khazaka), TEWL analyser CC01	Results for T300 are as follows: back (mean = 17.78, variance 1.26, SD 1.12), leg (mean 23.22, variance 5.87, SD 2.42), tail base (mean 26.58, variance 8.48, SD 2.91) and shoulder (mean 65.82, variance 7.81, SD 2.79). For the CCO1 it was: back (mean 20.56, variance 1.05, SD 1.02), leg (mean 23.4, variance 1.77, SD 1.33), tail base (mean 26.76, variance 5.9, SD 2.43), shoulder (mean 40.19, mean 0.58, SD 0.76). The lower variance and SD indicates more reliable results with the CC01.
Zhai et al.35	Tape stripping method in man: comparison of evaporimetric methods	10	Ten healthy patients (6 males, 4 females) had 10 or 20 strippings from bilateral forearms. Each patient/forearm was randomly allocated to have TEWL measurements using either an open or closed chamber device.	In vivo	Tewameter TM210 (Courage and Khazaka), Vapometer SWL‐3 (Delphin Technologies)	The closed chamber device showed a slightly higher (but not statistically significant) inter‐individual CV. Open chamber: 10 strips—mean TEWL 2.2 ± 0.9, CV (%) 41.7. 20 strips—TEWL 3.9 ±1.3, CV (%) 33.5. Closed chamber: 10 strips—2.4 ± 1.4, CV (%) 60.5%. 20 strips—TEWL 4.6 ± 2.2, CV (%) 47.8%.	There was no a statistically significant difference between two sites in measures by open and closed chamber devices, neither after 10 nor after 20 strips.

Abbreviations: AD, atopic dermatitis; ANOVA, analysis of variance; CI, confidence interval; CV, coefficient of variation; ICC, intra‐class correlation coefficient; LoA, limits of agreement; POSAS, The Patient and Observer Scar Assessment Scale; SC, stratum corneum; SD, standard deviation; SEM, standard error of measurement; SLS, sodium lauryl sulphate; TEWL, transepidermal water loss; THC, truncated hollow cone; VC, variation coefficient; WVTR, water vapour transmission rates.