Archives of Dermatological Research

, Volume 305, Issue 4, pp 315–323

Transepidermal water loss in young and aged healthy humans: a systematic review and meta-analysis

Authors

    • Department of Dermatology and Allergy, Clinical Research Center for Hair and Skin ScienceCharité-Universitätsmedizin Berlin
  • Andrea Lichterfeld
    • Department of Dermatology and Allergy, Clinical Research Center for Hair and Skin ScienceCharité-Universitätsmedizin Berlin
  • Ulrike Blume-Peytavi
    • Department of Dermatology and Allergy, Clinical Research Center for Hair and Skin ScienceCharité-Universitätsmedizin Berlin
Original Paper

DOI: 10.1007/s00403-012-1313-6

Cite this article as:
Kottner, J., Lichterfeld, A. & Blume-Peytavi, U. Arch Dermatol Res (2013) 305: 315. doi:10.1007/s00403-012-1313-6

Abstract

Transepidermal water loss (TEWL) is regarded as one of the most important parameters for characterizing skin barrier function but an agreed upon definition of what a “normal” TEWL is does not exist. In order to determine generalizable TEWL values for healthy adults, a systematic review and meta-analysis was conducted. The databases MEDLINE and EMBASE and publication lists were screened. After full-text appraisal of 398 studies, 231 studies were excluded due to unclear or insufficient reporting. 167 studies providing data about 50 skin areas were included in the final data synthesis. Pooled sample sizes ranged from n = 5 for the left cheek and the left lower back to a maximum of n = 2,838 for the right midvolar forearm area. The lowest TEWL of 2.3 (95 % CI 1.9–2.7) g/m2/h was calculated for the breast skin, the highest TEWL of 44.0 (39.8–48.2) g/m2/h for the axilla. TEWL in individuals being 65 years and above was consistently lower compared to the group of 18- to 64-year-old individuals. The quality of reporting TEWL in humans should be increased in future studies.

Keywords

AdultAgedDermatologyHumansMeta-analysis

Introduction

Transepidermal water loss (TEWL) is regarded as one of the most important parameters for skin barrier function. First descriptions for its measurement can be traced back until the 1940s and 1950s [3]. Today several TEWL measurement instruments with different technologies are commercially available and are used worldwide routinely in dermatological practice and research.

TEWL is a measure of the flux density of condensed water diffusing from the deeper highly hydrated layers of the dermis and epidermis to the skin surface and is usually expressed in g/m2/h. TEWL values are affected by the state and function of the stratum corneum (SC). There is convincing evidence today that increased TEWL is associated with skin barrier dysfunction whereas normal or decreased TEWL is regarded as an indicator for intact or recovered skin barrier [22, 37]. However, a precise definition of what a “normal” TEWL is does not exist. Among others TEWL is affected by the anatomic sites, climate conditions, and measurement devices including calibration, accuracy and many more [33, 37].

Above all, the association between physiological skin ageing, skin permeability barrier and baseline TEWL is conflicting and difficult to interpret [2, 47]. An often observed simultaneous decrease of TEWL and SC water content during skin aging is regarded as not affecting the skin barrier function and it is differentiated from pathologically dry skin with barrier impairments [6]. Due to decreasing TEWL during aging, the skin barrier was also described as “better than normal” [44] or even as skin barrier improvement [24]. Recent reviews suggest that there is still no clear consensus that TEWL actually decreases with age [2, 25, 26] and two recent studies found no TEWL differences between young and aged subjects [7, 17].

In order to determine generalizable baseline TEWL values that are “normally” to be expected in clinical practice and research, a systematic review and meta-analysis was conducted. The objective was to summarize available evidence about baseline TEWL in healthy adults taking especially skin areas and age into account.

Methods

Eligibility criteria

Studies had to meet the following inclusion criteria: (1) primary study report, (2) studies in humans, (3) in vivo measurements, (4) disease-free skin, (5) no systematic or topical treatments affecting the skin barrier function, (6) TEWL measured and reported [including measures of spread like standard deviations (SDs)] in descriptive non-interventional studies, (7) TEWL measured and reported (including measures of spread like SDs) at baseline and/or control without any intervention in experimental studies, (8) 18+ years and clear reporting of age, (9) Language English or German. Exclusion criteria were: (1) reviews, (2) animal studies, (3) TEWL measurements on nails, in vitro, in excised skin, (3) diseased skin, (4) 17 years or younger or unclear reporting of age, (5) TEWL measurement without reporting of sample size and/or spread parameters.

Information sources and search strategy

A concurrent search in the databases MEDLINE (1948–May 2012) and Embase (1947–May 2012) via OvidSP was conducted and last updated in June 4th (Table 1). Publication lists of three TEWL probe manufactures (Biox Ltd., UK; Delfin Technologies, Finland; Courage & Khazaka, Germany) and reference lists of all full text publications and reviews were screened for additional primary studies.
Table 1

Search strategy in MEDLINE and EMBASE using OvidSP (04.06.12)

#

Searches

Results

1

Water loss, insensible/ph (physiology)

426

2

TEWL.ti. or TEWL.ab. or transepidermal water loss.ti. or transepidermal water loss.af.

3,767

3

1 or 2

3,984

4

Epidermis/in, ph, pp (injuries, physiology, physiopathology)

1,923

5

Epiderm$.ti. or epiderm$.ab.

270,794

6

4 or 5

271,263

7

3 and 6

1,335

8

Limit 7 to human

818

9

Limit 8 to (English or German)

776

Study selection

Results from the data base search were screened by two reviewers independently. Eligibility of studies was evaluated based on title and abstract. Study IDs were assigned to included references after full-text reading. For all excluded studies the reasons for exclusion were noted.

Data collection

Following variables were extracted: Author, year, country, season, sample size, sex, mean age, skin photo type, ethnic origin, measurement conditions and procedures (e.g., temperature, rel. humidity), instrument, skin area, measured mean TEWL and corresponding spread values [SD, 95 % confidence intervals (CI), standard errors (SEs)]. Data were extracted from the text, tables or figures as presented or recalculated when necessary. The data extraction was conducted by two reviewers independently. Any disagreements were resolved by reading the original publication again.

Methodological appraisal

In clinical research and practice TEWL values are affected by various sources of variation, e.g. type of instrument, calibration, temperature and humidity, probe application, number of repeated measurements and many more [33, 37]. To the best of our knowledge there is no reference standard device producing the most accurate TEWL in humans in vivo. We also reviewed published studies comparing measurements of at least two TEWL instruments under comparable measurement conditions in humans in vivo [4, 10, 11, 14, 16, 18, 20, 38, 39, 41, 43] but detected no systematic differences between the devices across all studies (Online Resource 1). Therefore, we extracted the variables as described in the studies but did not perform weightings or other kinds of formal methodological appraisals.

Synthesis of results

The mean TEWL-value per skin area and study was regarded as the primary outcome. We used a random-effects model [12] to combine the TEWL measures per skin area of all studies in the meta-analysis. The inverse of the variance method was used to weigh the individual TEWL estimates. 95 % CIs were given for each summary measure. In order to detect the possible influence of age, we repeated this procedure for studies including 18- to 64-year-old and 65+ year subjects. Non-overlapping 95 % CIs were interpreted as statistically significant differences between groups. All studies were this distinction could not be made were excluded from this subgroup analysis. The mean age across all studies and across studies including only younger or older subjects was calculated by a simple weighted mean according to the sample size n of the individual studies. The softwares SPSS Statistics Version 19 (IBM, US) and StatsDirect Version 2.7.8 (StatsDirect Ltd, UK) were used for all analyses.

Results

Study selection and study characteristics

The study selection process is shown in Fig. 1. After removal of duplicates, 503 publications in MEDLINE and Embase and 1,905 publications from other sources were identified and screened. Finally 398 articles were read in full text. From the 398 assessed full text articles, 167 were included into the meta-analysis and 231 were excluded. The main reason for exclusion was that baseline TEWL measures and/or spread parameters were not reported (Online Resource 2).
https://static-content.springer.com/image/art%3A10.1007%2Fs00403-012-1313-6/MediaObjects/403_2012_1313_Fig1_HTML.gif
Fig. 1

Identification and selection process of studies

Characteristics of the included studies are shown in the Online Resource 3. The majority of the studies (n = 39) was conducted in the USA followed by studies from Germany (n = 22) and The Netherlands (n = 15). Twenty-three studies were from Asian countries including 14 studies from Japan. Data about seasons were available for 43 studies, skin type and/or ethnic origin was reported in 63 studies. In total there were 32 studies where gender was not reported. TEWL measurements in nearly all studies were performed in comparable temperature- and humidity-controlled conditions.

Synthesis of results

The main results of the meta-analysis are shown in Table 2 and in the Online Resource 4. In total 50 skin areas could be distinguished with sample sizes ranging from n = 5 (left cheek, left lower back) to a maximum of n = 2,838 for the right midvolar forearm. The lowest TEWL of 2.3 (95 % CI 1.9–2.7) g/m2/h was reported for the breast, the highest TEWL of 44.0 (39.8–48.2) g/m2/h for the axilla.
Table 2

Summary of pooled TEWL estimates and comparison between young and aged group

Skin area

All studies

Studies including 18–64 years subjects

Studies including 65+ years subjects

Number of studies

Sample size (n)

Mean age (years)

TEWL estimate (95 % CI)

Number of studies

Sample size (n)

Mean age (years)

TEWL estimate (95 % CI)

Number of studies

Sample size (n)

Mean age (years)

TEWL estimate (95 % CI)

(1) Scalp

1

125

41.3

11.0 (10.3–11.7)

1

125

41.3

11.0 (10.3–11.7)

(2) Forehead left

2

18

41.5

15.6 (12.9–18.3)

(3) Forehead mid

2

18

41.5

20.7 (16.7–24.7)

(4) Forehead right

26

748

39.9

13.8 (12.3–15.4)

17

644

36.4

15.8 (13.5–18.0)

3

40

72.8

7.4 (7.1–7.7)

(5) Upper eyelid

3

42

38.8

11.7 (8.7–14.8)

2

32

27.9

11.8 (7.4–16.2)

1

10

73.6

11.6 (9.1–14.1)

(6) Periocular

7

368

45.0

12.3 (11.5–13.1)

5

174

36.4

11.7 (10.8–12.6)

(7) Nose

3

42

38.8

11.8 (7.1–16.6)

2

32

27.9

12.8 (6.2–19.4)

1

10

73.6

9.8 (7.1–12.5)

(8) Lip

1

303

49.0

35.0 (33.5–36.5)

(9) Cheek left

1

5

29.0

11.6 (9.8–13.4)

1

5

29.0

11.6 (9.8–13.4)

(10) Cheek right

34

1,200

42.2

15.4 (13.9–17.0)

18

669

35.2

14.5 (12.9–16.1)

1

10

73.6

7.1 (5.1–9.1)

(11) Nasolabial left

2

32

25.0

26.8 (21.4–32.2)

2

32

25.0

26.8 (21.4–32.2)

(12) Nasolabial right

4

52

35.3

21.5 (14.4–28.5)

3

42

26.1

22.2 (14.1–30.3)

1

10

73.6

18.6 (11.0–26.2)

(13) Perioral

2

20

51.7

13.1 (9.7–16.5)

1

10

29.8

15.8 (8.6–23.0)

1

10

73.6

12.3 (8.4–16.2)

(14) Postauricular

8

88

46.8

6.8 (5.8–7.7)

3

36

27.0

6.7 (4.7–8.7)

2

30

72.5

6.2 (5.9–6.6)

(15) Chin

3

25

47.2

11.6 (9.9–13.4)

2

15

29.5

11.6 (8.7–14.6)

1

10

73.6

10.9 (8.3–13.5)

(16) Neck

3

70

33.3

7.1 (4.8–9.5)

2

60

26.3

7.0 (3.0–11.0)

1

10

73.6

7.9 (6.3–9.5)

(17) Breast

1

18

24.0

2.3 (1.9–2.7)

1

18

24.0

2.3 (1.9–2.7)

(18) Areola

1

18

24.0

3.4 (2.2–4.6)

1

18

24.0

3.4 (2.2–4.6)

(19) Axilla

1

125

41.3

44.0 (39.8–48.2)

1

125

41.3

44.0 (39.8–48.2)

(20) Upper arm

20

362

47.4

5.3 (4.4–6.1)

8

207

33.7

6.2 (4.9–7.5)

6

91

72.8

4.7 (3.6–5.9)

(21) Elbow ventral

3

239

44.3

9.4 (4.0–14.7)

2

215

40.8

12.4 (11.9–12.9)

(22) Proximal left volar forearm

1

90

40.0

12.5 (12.0–13.0)

1

90

40.0

12.5 (12.0–13.0)

(23) Proximal right volar forearm

5

49

36.8

4.3 (2.6–5.9)

3

31

34.1

2.7 (2.4–3.0)

(24) Midvolar left forearm TEWL

17

433

37.1

8.7 (6.5–10.8)

13

348

36.9

9.6 (6.8–12.5)

1

10

73.6

2.7 (1.9–3.5)

(25) Midvolar right forearm

148

2,838

35.8

6.5 (6.2–6.8)

109

2,206

32.9

6.6 (6.3–6.9)

4

46

73.8

3.5 (2.3–4.6)

(26) Distal left volar forearm

4

141

37.7

14.9 (7.2–22.6)

3

123

39.1

18.5 (12.0–24.9)

(27) Distal right volar forearm

7

82

36.8

9.6 (7.3–11.8)

5

64

35.5

10.7 (7.0–14.4)

(28) Forearm left dorsal

9

114

44.1

3.9 (2.9–5.0)

3

45

29.2

6.5 (4.6–8.4)

1

15

70.5

3.0 (2.6–3.4)

(29) Forearm right dorsal

8

180

52.0

4.8 (3.7–6.0)

4

110

38.9

5.3 (4.4–6.2)

3

46

70.7

4.4 (2.5–6.3)

(30) Hand left back

2

608

40.4

21.2 (4.2–38.0)

2

608

40.4

21.2 (4.2–38.0)

(31) Hand right back

15

849

39.8

14.7 (11.9–17.6)

7

740

39.0

16.1 (9.0–23.1)

(32) Palm left

2

133

40.9

42.2 (40.3–44.1)

2

133

40.9

42.2 (40.3–44.1)

(33) Palm right

13

310

43.4

36.3 (29.5–43.1)

6

207

35.8

43.3 (32.6–54.1)

2

30

72.5

20.7 (19.8–21.7)

(34) Chest

3

37

26.7

8.6 (6.8–10.5)

3

37

26.7

8.6 (6.8-10.5)

(35) Abdomen

12

205

47.1

5.4 (4.0–6.9)

5

115

32.9

6.9 (3.5–10.4)

2

30

72.5

2.6 (2.5–2.7)

(36) Back left upper

2

130

40.7

8.9 (8.2–9.5)

2

130

40.7

8.9 (8.2–9.5)

(37) Back right upper

15

216

44.7

4.9 (4.2–5.6)

7

124

33.4

6.4 (5.4–7.3)

2

30

72.5

3.8 (3.6–4.0)

(38) Back mid

9

129

32.8

6.5 (4.8–8.2)

4

70

24.8

8.6 (5.8–11.4)

(39) Back left lower

1

5

24.5

8.2 (6.1–10.3)

1

5

24.5

8.2 (6.1–10.3)

(40) Back right lower

7

102

51.8

5.6 (4.0–7.1)

4

48

26.8

7.3 (5.4–9.2)

2

30

72.5

3.4 (3.3–3.5)

(41) Buttock

1

24

76.0

3.6 (2.8–4.4)

(42) Thigh

11

197

40.6

5.1 (4.1–6.1)

7

152

33.1

6.1 (4.1–8.1)

2

30

72.5

3.0 (2.9–3.1)

(43) Labia majora

7

131

39.5

16.8 (14.6–19.0)

4

96

30.8

17.6 (14.3–20.8)

(44) Shin

1

24

76.0

2.8 (2.3–3.3)

(45) Calf

7

251

39.9

9.2 (5.7–12.7)

5

216

34.4

9.6 (6.9–12.2)

(46) Leg medial

1

90

82.5

4.5 (4.1–4.9)

1

90

82.5

4.5 (4.1–4.9)

(47) Leg lateral

8

229

56.6

6.7 (5.5–7.9)

4

85

29.4

8.6 (5.6–11.6)

2

102

81.4

7.9 (0.1–15.6)

(48) Ankle

6

73

50.7

6.0 (4.6–7.5)

2

28

26.8

11.8 (9.8–13.8)

2

30

72.5

4.5 (3.9–5.2)

(49) Foot arch

3

183

42.5

41.0 (24.5–57.4)

2

159

37.4

50.2 (36.9–63.6)

(50) Foot back

1

125

41.3

18.0 (15.9–20.1)

1

125

41.3

18.0 (15.9–20.1)

TEWL was reported in 152 studies for 44 skin areas in 18- to 64-year-old subjects. In this young group pooled mean ages range between 24 and 41 years. TEWL estimates for 65+ years subjects were reported in 11 studies for 22 skin areas with pooled sample sizes between n = 10 (upper eyelid, nose, right cheek, right nasolabial area, perioral area, chin, neck, left midvolar forearm) and n = 102 (lateral leg area). Pooled mean ages ranged from 71 to 83 years.

Comparisons between both age groups were possible for 21 skin areas. Mean TEWL in the aged group was statistically significantly lower compared to the middle aged group in 11 skin areas. With one exception (neck) pooled TEWL estimates of remaining skin areas were also always lower, but without reaching statistical significance.

Discussion

This systematic review and meta-analysis aimed at summarizing available empirical evidence about TEWL in healthy human adults. We are able to provide estimates of 50 skin areas from head to toe presenting a comprehensive mapping of the human body. Because we pooled TEWL values measured with various devices under various assessment conditions from many geographical locations results can be regarded as largely generalizable.

This meta-analysis confirms that TEWL varies largely between skin areas that might be related to corneocyte size, turnover rate and corneocyte maturity at the respective anatomical locations [30, 42]. As pointed out by Menon and Kligman [29] there clearly is “no single optimal TEWL for the entire skin” but the question is whether the skin barrier function is good enough to allow survival. On the other hand, calculated ranges of the 95 % CIs of the pooled TEWL estimates suggest that inter individual differences are comparably low for most skin areas. Therefore, results can be regarded as current TEWL reference values for clinical evaluation and decision making and for effect or sample size determination in clinical trials.

For planning and analyzing clinical trials it is important to realize TEWL baseline differences on tightly adjacent skin areas. For example the right volar forearm is the most often used skin area in dermatological research. Results of previous single studies [8, 9, 28, 32] indicate varying TEWL from distal to proximal causing randomization problems across the whole volar skin area. Our findings indicate a clear and statistically significant TEWL increase from proximal (4.3 (95 % CI 2.6–5.9)) to distal (9.6 (95 % CI 7.3–11.8)) on the right volar forearm skin. A comparable trend could also be observed for the left volar forearm but results show much larger variations.

This meta-analysis suggests that TEWL is usually lower in aged humans compared to middle aged adults. However, statistically significant differences were only found for 11 out of 21 possible comparisons. This might be explained by the absence of real differences indicating that the TEWL is the same in both groups or that sample sizes were too low and/or variation was too high between included studies. One the other hand, TEWL estimates in the aged group were never higher indicating that reduced TEWL in old age is highly likely. These findings contradict recent suggestions that there is no association between TEWL and age [17] or even an increase with increasing age [40].

The reason for decreased TEWL in aged individuals seems not to be fully understood today. Increasing corneocyte surface areas causing increasing SC transit times for water in aged individuals might be one explanation [5, 26]. Skin areas with larger corneocytes are usually associated with lower TEWL [30]. Based on finite element modeling, Xiao and Imhof recently showed that the SC water diffusion resistance increases with increasing corneocyte sizes. Therefore, the SC water diffusion flux decreases and so the water flux from the SC surface [48]. The influence of SC thickness on TEWL is also frequently discussed. While Waller and Maibach in their review [47] concluded that there are little or no differences in SC thickness between young and aged adults, there is evidence that the SC thickness decreases with in intrinsic skin aging [27] but that SC thickness seems to increase in photo damaged skin [45]. When looking closely into Table 2 it seems indeed that TEWL differences between young and old are larger in the primarily intrinsically aged skin areas (e.g. volar forearm, abdomen, back) compared to primarily extrinsically aged skin (e.g., dorsal forearm, nasolabial area, neck). This would indicate that TEWL of photo damaged skin is higher than in intrinsically aged skin but this is not a sufficient explanation for the reasons for a general decreased TEWL in the aged. Besides the anatomy and size of the corneocytes it is also known that the composition of the SC lipid bilayers directly influences the skin barrier function [34]. Therefore, the decreasing SC lipid content with aging might also contribute to decreasing TEWL [2, 19, 36]. Because the water diffusion coefficient of lipids is assumed to be 10 times higher than the water diffusion coefficient of the corneocytes [48] an overall reduction of SC lipids will consequently decrease the average diffusion coefficient over the whole SC thickness. Finally, corneodesmosomes play important roles in SC integrity and skin barrier function. Because corneocytes become “flatter” with aging the anatomy of the corneodesmosomes might also change. Maybe a reduced activity of enzymes for the proteolysis of corneodesmosomes as often observed in the SC in dry skin plays also a role here.

Despite these structural and biomechanical explanations the clinical relevance of the decreased baseline TEWL is unclear. How morphological age-related changes really translate into functional compromises in aged skin is difficult to explain [21]. Among others it seems unlikely that baseline TEWL can predict skin response [1]. Skin stress tests like repeated tape strippings seem to be more able to reveal clinically relevant functional differences between young and aged skin [19].

One of the most important finding of this review is the poor quality of reporting of TEWL estimates in the literature. We excluded more than 200 studies due to the absence of reported baseline values, missing spread parameters or unclear reporting of sample characteristics. It is true that due to the many influencing factors TEWL is a more relative than an absolute parameter [37] and therefore intra individual changes are easier to interpret than between group comparisons but comprehensive reporting of baseline measures is a crucial element in every scientific study report [31, 46]. Based on the EEMCO [36], on the Standardization Group of the European Society of Contact Dermatitis [32] guidelines and based on our findings we recommend reporting the following minimum details:
  • Sample size (not included but measured subjects)

  • Sample characteristics: age, gender, ethnic background, skin status.

  • Skin area including reporting of left/right side.

  • Measurement device and procedure, e.g. number of replicates.

  • Measurement conditions: season, geographic location, relative humidity, temperature, acclimatization.

  • TEWL point estimates including SDs.

Based on the specific research questions many more details need to be taken into account before such a study is conducted which should be reported afterwards. Increasing the reporting quality in future TEWL studies would increase our knowledge about skin barrier characteristics in a wide range of conditions.

Furthermore, our results indicate that TEWL in aged individuals is largely unexplored. Out of 167 studies we identified only 11 reports providing data for 22 skin areas. Consequently the pooled sample sizes are comparably small which limits the generalizability to a certain extent. The proportion of aged individuals increases worldwide and therefore the prevalence of age-related diseases like xerosis cutis increases [13, 35]. It is widely agreed upon that adequate skin care interventions can promote skin barrier function in aging skin [15, 23] and therefore clinical studies in this population are likely to become more frequent in the future. Increasing our knowledge about skin barrier function in this population is of utmost importance.

Limitations

One limitation of this systematic review might be the high proportion of excluded studies. Due to poor reporting we were unable to consider a large amount of empirical TEWL measurements that might have changed our results. Furthermore, we might have missed publications due to our search strategy. However, we used a sensitive data base search and screened hundreds of studies from reference lists and from lists created by manufactures.

Another limitation might be the way of statistical synthesis of TEWL values. We assumed a random effects model taking heterogeneity into account but one can still argue whether it is appropriate to summarize TEWL estimates produced by different devices, in different measurement conditions, in persons with different ethnical backgrounds and many more. In our data extraction strategy, we considered many of these variables but due to the large amounts of missing information we are currently unable to perform more detailed subgroup analyses. Interestingly nearly all measurements (Online Resource 3) were conducted in highly comparable temperature- and humidity-controlled conditions as suggested in the EEMCO guidelines [37] and by the Standardization Group of the European Society of Contact Dermatitis [33]. There is also evidence that readings of available measurement devices are not identical but highly correlated [14, 16, 41]. On the other hand, there is no evidence that there is one device that is most accurate. As long as there are no proofs that one device is clearly superior to the others it is reasonable to assume that the “true” population TEWL is somewhere in between. We plan to add all upcoming studies to our database to do more powerful group comparisons in the future.

Conclusions

TEWL is a widely applied parameter to indicate skin barrier function. This is the first attempt to summarize available empirical TEWL estimates of the human body. While there are many studies focusing on “traditional” skin areas for research there is only little knowledge about other anatomic locations. TEWL in 65-year and older individuals seems to be generally lower compared to middle aged individuals but available evidence is too sparse to draw firm conclusions yet. TEWL in aged individuals seems to be generally underexplored. Future publications presenting TEWL measurements should include means and standard deviations for all TEWL estimates, details about measurement conditions, sample characteristics including ethnic origin, gender and age, and geographic and climate conditions.

Acknowledgments

This research was supported by the Clinical Research Center for Hair and Skin Science, Department of Dermatology and Allergy, Charité-Universitätsmedizin Berlin, Germany.

Supplementary material

403_2012_1313_MOESM1_ESM.pdf (22 kb)
Supplementary material 1 (PDF 22 kb)
403_2012_1313_MOESM2_ESM.pdf (181 kb)
Supplementary material 2 (PDF 180 kb)
403_2012_1313_MOESM3_ESM.pdf (296 kb)
Supplementary material 3 (PDF 295 kb)
403_2012_1313_MOESM4_ESM.pdf (324 kb)
Supplementary material 4 (PDF 324 kb)

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