Potential for irritation increases from the wrist to the cubital fossa

Unbearable transepidermal water loss (TEWL) experimental variability: why?

Despite the wide breadth of research, much disparity exists in transepidermal water loss (TEWL) research data-possibly due to uncontrolled experimental variables. We determined whether such experimental variables significantly impact TEWL studies and cause this disparity. An initial literature search regarding TEWL was performed to determine potential confounding variables. A subsequent search procured relevant and representative studies investigating the impact of these variables on TEWL. Variables, such as age, anatomic site, and temperature, impact TEWL and should be controlled for in TEWL studies. Other variables, such as smoking and menstrual cycle, have inconclusive results or do not provide sufficient data breadth to make a conclusion regarding its effect, if such an effect exists, on TEWL metrics. Therefore, these variables require further research to determine their potential impact on TEWL. Matching for as many experimental variables as possible may reduce the disparity in TEWL data/conclusions.

Comparison of mechanical, chemical and physical human models of in vivo skin damage: Randomized controlled trial

INTRODUCTION

Human in vivo models of skin damage were often used in research of cutaneous disorders. The most commonly used models were tape-stripping as mechanical, sodium lauryl sulphate-induced irritation as chemical and ultraviolet radiation as physical damage model. In regard to differences between models, they were expected to have different responses to damage and recovery, with unique skin parameters' changes over time.

OBJECTIVE

The aim was to compare skin parameters in three different skin damage models on the same anatomical location, with and without topical treatment.

METHODS

Four test sites on each forearm were randomly assigned to three skin damage models with the fourth sites on each forearm chosen as a control, undamaged site. Skin parameters were assessed using non-invasive methods.

RESULTS

Sodium lauryl sulphate irritation caused the strongest damage with delayed reaction to the irritant. Tape stripping leads to highest initial skin barrier disruption but afterwards it showed the fastest skin recovery. Ultraviolet radiation did not affect skin barrier function, but it elevated skin erythema and melanin level. Tested preparation did not lead to changes in measured parameters.

CONCLUSION

The skin of the participants had different response to three skin damage models with distinct changes of skin parameters and recovery. The trial was registered at ClinicalTrials.gov under the identifier NCT03783819.

Site variations in susceptibility to SLS

According to the European Society of Contact Dermatitis (ESCD) guidelines on the sodium lauryl sulfate (SLS) exposure test 'the flexor side of forearm skin with cubital fossa and wrist excluded is the preferred study site'. In this study we analysed the exact anatomic region within the suggested test area in respect to the outcome of the SLS exposure test. 3 test areas at the volar forearm were chosen: 'distal' with a 5-cm distance to the wrist, exact 'midvolar' and 'proximal' with a 5-cm distance to the cubital fossa. 25 healthy volunteers were irritated for 24 hr with 1% SLS. Transepidermal water loss (TEWL) measurements were taken before and 1 and 24 hr after removal of Finn Chambers((R)). Median baseline TEWL showed no significant differences in the 3 test sites. However, postexposure TEWL proximal was significantly (P < 0.01) higher than midvolar and distal. The distal volar forearm showed the lowest TEWL 24 h after the irritation. The differences were in comparison to midvolar (P < 0.01) and proximal (P < 0.001) significant. The results show that it is essential to point out the exact position of the test area at the volar forearm in study reports and to randomize the irritation areas at the volar forearm if different treatments are to be compared.

Anti-irritants I: dose–response in acute irritation

The term 'anti-irritant' (AI) was coined in 1965 by Goldemberg to describe a diverse group of topical product ingredients, which were able to reduce the irritation potential of other more irritating ingredients in the same product. 'AIs' are being added to cosmetic formulations in order, allegedly, to benefit tolerability of the products and allow claims such as 'soothing' and 'healing' ingredients. Limited documentation in favour of the efficacy of AIs is published. We studied the dose-related effect of 4 alleged AIs (nifedipine, (-)-alpha-bisabolol, canola oil and glycerol) on experimentally induced acute irritation in healthy volunteers. Each AI was used in 3 concentrations. Acute irritation was induced by occlusive tests with 1% sodium lauryl sulfate and 20% nonanoic acid in N-propanol. The irritant reactions were treated twice daily with AI-containing formulations from the time of removal of the patches. Evaluation of skin irritation and efficacy of treatments were performed daily for 4 days using clinical scoring, evaporimetry (transepidermal water loss), hydration measurement and colourimetry. Only glycerol showed dose-response and effects potentially better than no treatment. There was no significant effect and no difference between the three other AIs.

The hairless guinea-pig as a model for treatment of cumulative irritation in humans

BACKGROUND

The effect of six skin-care formulations (SCFs) on experimentally induced cumulative irritation was studied in hairless guinea-pigs (HLGPs) and in human volunteers (HVs). The formulations were a basic cream, a carbomer cream and four modifications of the carbomer cream, containing either 10% isopropyl palmitate (IPP cream), 10% glycerol (glycerol cream), 19.5% canola oil (canola oil cream) or 0.5% (-)-alpha-bisabolol (bisabolol cream).

METHODS

In HLGP, irritant dermatitis was induced with 30 min daily exposure for 4 days to 0.5% sodium lauryl sulfate aq. (SLS). In HVs, irritant dermatitis was induced with 10 min daily exposure for 5+4 days (no irritation on weekends) to 3% SLS aq. on the right and 30% nonanoic acid (NON) in n-propanol on the left volar forearm. Clinical scoring was performed daily; evaporimetry (total epidermal water loss (TEWL)), hydration and colorimetry were measured at baseline (day 0) in the middle and at the end of treatment. Treatments were applied twice daily. The basic cream and the IPP cream were excluded from testing in HLGP because they were known from previous studies to be irritant in HLGP, while all formulations were known to be equally and well tolerated locally in humans.

RESULTS

All formulations worsened the skin irritation in HLGP: the glycerol cream the least, the canola oil cream the most, while the bisabolol cream and the carbomer cream were indistinguishable. In humans, the glycerol cream was better than 'No Treatment' after cumulative irritation with both SLS and NON. The basic cream was better tolerated in humans than was expected from previous testing in HLGPs.

CONCLUSION

In conclusion, the results from the studies in HLGPs and HVs are in agreement with regard to ranking of the SCFs. Further, the glycerol cream showed a positive treatment effect on both SLS- and NON-irritated skin in HVs.

Variation of skin properties within human forearms demonstrated by non-invasive detection and multi-way analysis

BACKGROUND/AIM

It is known that the properties of human skin vary locally. The purpose of this study was to investigate the properties of human volar forearms even further using advanced non-invasive techniques and numerical methods.

METHODS

The skin properties of human volar forearms were investigated using measurements of trans epidermal water loss and multifrequency electrical impedance. Eight sites on the forearms of 27 healthy volunteers were measured. The sites were oriented as squares, four sites on both left and right forearm, approximately 40-50 mm apart.

RESULTS

Analysis of variance showed significant differences for epidermal water loss (P < 0.01) and the skin impedance (P < 0.001) between the inner and outer sides of the arms. Additionally, parallel factor analysis of the full skin impedance spectra also showed that there are systematic differences between right and left arm (P < 0.01).

CONCLUSION

It is crucial to design skin studies carefully in order to minimise the effects of the local skin properties of human skin.

Intra-individual variations in acute and cumulative skin irritation responses

It is well-known that humans show a wide range of variation in skin reactivity to irritant chemicals. This has been established through population studies, through the examination of inter-subject variability, and (to a limited extent) through studies of skin site variation in response within subjects. However, simple response variability within individual test subjects has not been examined as carefully, and this has implications for our ability to predict irritant reactivity. Some key questions are: (i) how consistently do human beings respond, even within a given study, to different equally irritating chemicals, or to the same chemical when comparing different concentrations or durations of exposure, and, (ii) Do individual test subjects' responses to one chemical (or exposure scenario) correlate with their responses to another? To examine these questions in some detail, we reexamined individual study subjects' responses from earlier published studies involving both acute and cumulative irritation patch test protocols. Acute irritation responses were compared across chemicals with similar irritation profiles. Cumulative irritation responses were compared across different concentrations of the anionic surfactant, sodium dodecyl sulfate (SDS). Acute (high concentration) and cumulative (low concentration) patch test responses to SDS were also compared. The analysis showed that, as might be expected, response correlations were greatest within test types, either when comparing chemicals of similar overall irritancy, or when comparing similar concentrations of a single chemical. However, individually divergent responses were also frequent, reinforcing the conclusion that a given individual's response to one chemical or exposure condition does not always predict their response to another. This has important ramifications for other questions related to population differences in skin reactivity.

Evaluation of skin viscoelasticity and anisotropy by measurement of speed of shear wave propagation with viscoelasticity skin analyzer

Skin viscoelasticity was evaluated by a fast, noninvasive assay based on the measurement of the speed of elastic shear wave propagation in the skin by a new portable and user-friendly viscoelasticity skin analyzer. The range of speed of elastic shear wave propagation measured by viscoelasticity skin analyzer allows the evaluation of the stiffness of a wide spectrum of artificial materials as well as the viscoelasticity of skin of laboratory animals and human subjects. The directional nature of the measurement enables to monitor the anisotropy of the materials tested. The speed of elastic shear wave propagation was shown to have a positive correlation with the stiffness of the material tested. In symmetric contralateral areas of intact skin in rabbit ears, similar viscoelasticity and anisotropy were observed. Twenty-four hours after the induction of local edema by croton oil, skin stiffness and anisotropy were significantly increased. In healthy human subjects of both sexes significant variations in skin stiffness and anisotropy were observed in three different skin areas along the forearms, but the speed of elastic shear wave propagation was similar in the symmetric contralateral areas. Age (17-65 y) seemed to have a limited effect on the viscoelasticity of the forearm skin. Hydrating creams decreased the stiffness of the forearm skin for only approximately 3 h. The stiffness and anisotropy of the skin of the breasts in female volunteers (20-86 y) increased with age, but the speed of elastic shear wave propagation was similar in symmetric contralateral areas in the same individuals. Based on these results, we propose the application of the viscoelasticity skin analyzer in experimental and clinical practice for quantitative evaluation of skin condition.

Comparison between 2 test models in evaluating the effect of a moisturizer on irritated human skin

The purpose of the present study was to compare 2 experimental models of moisturizer efficacy on the recovery of irritated skin on the hands and the volar forearms. 12 healthy volunteers had their hands immersed in sodium lauryl sulfate (SLS) 10 min 2x daily for 2 days, and at the same time the volunteers had patch tests with SLS (0.125%, 0.25% and 0.5%) applied on their forearms for 24 h. After irritation of the skin, the volunteers had a moisturizer applied on one arm/hand 3x daily for the following 9 days. The other arm/hand served as untreated control. Evaluation was done on days (D) 1, 3, 5, 8 and 12 by transepidermal water loss, electrical capacitance, laser Doppler flowmetry and DermaSpectrometry. Both models were found useful, and the moisturizer was found to accelerate regeneration of the skin barrier function in both the hands (D8, p<0.05) and the volar forearms (0.5% SLS, D5 and D8, p<0.01). When the forearm model is used in the present set-up, a relatively high concentration of SLS (>0.25%) should be used and evaluation measurements are best performed on D5-D8. The forearm model proved reliable and easy to handle and we suggest that this model is used in future studies on moisturizer evaluation.

Intra-and inter-individual variations in transepidermal water loss on the face: facial locations for bioengineering studies

The volar forearm is the favored location for bioengineering studies. However, transepidermal water loss (TEWL), which is an important indicator of the function of the epidermal barrier, shows regional variations, and for the evaluation of cosmetic formulations, facial skin would be more suitable. In this study, we have compared 10 facial locations with 1 test site on the volar forearm for absolute TEWL values, reproducibility, and correlation. Measurements were performed over 3 consecutive days. The TEWL values of the facial test sites were higher compared to forearm values and did not correlate with the forearm. On the face, there was a good correlation between the values of the right compared to the left side of the face. The sites superior to the nervus supraorbitalis, the medial borders of the musculus masseter, and the center of the chin proved to be locations with relatively stable TEWL values. There was a greater variability at the center of the forehead and at the center of the cheeks. It is recommended that TEWL measurements on facial locations with stable TEWL values are used for the evaluation of cosmetic formulations.

Effect of barrier perturbation on cutaneous salicylic acid penetration in human skin: in vivo pharmacokinetics using microdialysis and non-invasive quantification of barrier function

We have used microdialysis in the dermis for assessing penetration kinetics of salicylic acid (SA) in healthy volunteers (n = 18), following application on the volar aspect of the left forearm. Penetration was monitored at four locations: in normal (unmodified) skin and in skin with perturbed barrier function from (i) repeated tape stripping (ii) irritant dermatitis from 1 or 2% sodium lauryl sulphate (SLS) for 24 h and (iii) delipidization by acetone. The order of the treatments was randomized according to a latin square design. Epidermal barrier function and skin irritation were assessed in each location using evaporimetry and colorimetry. Transepidermal water loss (TEWL) values confirmed that both mild (acetone), moderate (1% SLS) and severe barrier damage (tape stripping and 2% SLS) had occurred. Microdialysis sampling with two parallel probes in the dermis was performed in each of the four treatment areas for every subject. SA (5% in ethanol) was applied in a chamber glued to the skin overlying the microdialysis probes and sampling was continued for 4 h. SA was detectable in all samples and measurable in all samples from penetration through perturbed skin. Comparing the SA penetration in barrier-perturbed skin with the penetration in unmodified skin in the same subject, the mean SA penetration increase was 2.2-fold in acetone-treated skin (P = 0.012), 46-fold in mild dermatitis and 146- and 157-fold in severe dermatitis and tape stripped skin, respectively (P < 0.001). The penetration of SA significantly correlated with the measurements of barrier perturbation by TEWL (P = 0.01) and erythema (P = 0.02) for each individual. Microdialysis sampling of SA penetration was more sensitive than non-invasive measuring techniques in detecting significant barrier perturbation in acetone-treated skin. A positive dose-response relationship for the percutaneous penetration of SA in response to increasing SLS pretreatment concentrations and thus the degree of irritant dermatitis was found. When analysing data by location on the forearm, a tendency towards an intraregional variation in the reactivity to barrier damage was found, with the most proximal location displaying higher reactivity scores than the most distal location in response to the same barrier perturbation procedures. The penetration of SA was not significantly different between locations. In conclusion, using microdialysis in the dermis to obtain real-time dermal pharmacokinetics in the target organ, this study demonstrates highly increased and differentiated cutaneous penetration of SA in barrier-perturbed skin. The measured drug penetration was demonstrated to correlate with non-invasive quantification of barrier damage.

Regional differences in stratum corneum reactivity to surfactants. Quantitative assessment using the corneosurfametry bioassay

The skin does not react similarly to the presence of xenobiotics over all anatomic sites. Distinct regional differences have been described for irritancy and percutaneous absorption. The present study assesses the regional variation of stratum corneum reactivity to surfactants using the corneosurfametry bioassay. Stratum corneum was harvested from 6 body sites in 20 young adults. Corneosurfametry was performed using water, 1% SLS and a 5% soap solution. Data show that the best variable to assess regional variability in irritancy is the overall difference in corneosurfametry (ODC), comparing the effect of a given surfactant with water. The dorsal hand and volar forearm were the least reactive, the neck, forehead, back and dorsal foot the most reactive, sites. It is concluded that the corneosurfametry bioassay, through the ODC variable, is a practically noninvasive tool for the evaluation of regional variation in irritancy at the level of the stratum corneum.

Guidelines on sodium lauryl sulfate (SLS) exposure tests. A report from the Standardization Group of the European Society of Contact Dermatitis

This report reviews the clinical and histopathological reactions caused by sodium lauryl sulfate (SLS), and the non-invasive methods that can characterize these reactions. Furthermore, SLS exposure techniques and factors that may influence the outcome of these exposures are discussed. Finally, guidelines are introduced for each exposure technique in order to have a uniform approach to SLS testing in man. Since different study aims warrant different testing conditions, we have proposed 2 categories, namely susceptibility testing and provocative testing, tailored to the aim with which the study is performed.

Olive oil--contact sensitizer or irritant?

Adverse cutaneous reactions to topically applied olive oil are seldom reported, and positive patch tests to it are mostly regarded as allergic. To evaluate such "positive" patch test reactions, 77 female (mean age: 44 years) and 23 male eczema patients (mean age: 46 years) were prospectively patch tested with freshly prepared olive oil. Tests were performed openly (including ROAT) as well as using Al-tests and Finn Chambers on Scanpor. 5 patients (2 male) showed "positive" test reactions (all patients at the Al-test site, 3 at the Finn Chamber site, 1 with ROAT). In only 1 patient could the reaction be classified as probably allergic, in contrast to previous reports. In conclusion, olive oil is very weakly irritant in general, but bears relevant irritant capacity when applied under occlusive conditions. Therefore, olive oil appears to be less than suitable for the topical therapy of patients with venous insufficiency and associated eczema of the lower extremities.

Irritant effects of a detergent in wash, chamber and repeated open application tests

Development of irritant contact reactions in a wash test, in a repeated open application test (ROAT) and in chamber tests were compared with each other in 14 atopic and 14 non-atopic Caucasian medical students. In the wash test, the students washed their upper arm skin with 10% dishwashing liquid for 1 min 2 x a day for 1 week. In the ROAT, they applied the same detergent solution to 1 antecubital fossa 2 x daily for 1 week. Chamber tests were performed with the same detergent using 8 mm, 12 mm and 18 mm Finn Chambers applied to the upper back skin for 48 h. Additional 4 h and 24 h occlusion times were used with the 12 mm Finn Chambers. Test results were evaluated on days 0, 2, 4 and 7 by eye and by using an Evaporimeter EP1 for transepidermal water loss and a Minolta Chroma Meter CR-200 for skin colour. No statistically significant differences between atopics and non-atopics were found in any of the tests. The results of the tests did not correlate with each other, with the exception of the 12 mm/48 h chamber test and the wash test in atopics (R = 0.61, p = 0.02). It seems that other individual factors in addition to atopy influence the development of irritant contact dermatitis. The results of the chamber test and ROAT predicted poorly the result of the wash test.

Assessment of skin irritancy by 2 short tests compared to acute irritation induced by sodium lauryl sulfate

Irritant contact dermatitis is a very common disease that is preventable by protective measures. The development of screening methods to identify subjects with increased susceptibility to irritants is essential to reduce the incidence of this disorder in the workplace. On the outlook for such methods, 2 quick non-invasive tests for irritability of the skin were compared to reliable, but time-consuming, patch testing with sodium lauryl sulfate (SLS). In 20 healthy volunteers, 0.5% SLS was applied on the medial 1.3 of the forearm for 23 h in order to induce experimental irritant contact dermatitis. On the same part of the forearm, 3 concentrations of dimethylsulfoxide (DMSO) and a solution of 0.2 mol/l NaOH were applied for 5 min. Assessment of skin irritability was made by visual scoring and measurement of transepidermal water loss. No correlation between the "quick tests" and SLS patch testing was found, indicating that these tests assess different mechanisms of irritation.

The sodium lauryl sulfate model: an overview

Irritant contact dermatitis is a complex entity with several clinical forms (acute, cumulative, etc.) and multiple mechanisms. Sodium lauryl sulfate (SLS), the most widely utilized model for studying acute and cumulative irritation, has proved highly practical and informative for such studies. This article summarizes several decades of investigation, and provides details of dosing, application method (closed versus open), and biologic endpoints (visual grading, transepidermal water loss) that may be utilized in future studies.

Efficacy of topical corticosteroids on irritant skin reactions

Topical corticosteroids are frequently used in the treatment of irritant contact dermatitis (ICD). The efficacy of this treatment has, however, not been thoroughly established, and experimental studies on the topic have provided conflicting results. The aim of the present study was to evaluate the effect of potent topical corticosteroids on experimentally-induced irritant skin reactions in a double-blind, vehicle-controlled study. 16 healthy volunteers had sodium lauryl sulfate patch tests symmetrically applied to the upper arms. After removal of patch tests, a potent topical corticosteroid (betamethasone-17-valerate) was applied to the irritant skin reaction on one arm, while the corresponding vehicle was applied to the irritant skin reaction on the opposite arm 2x daily for 7 days. Reactions were evaluated by measurement of transepidermal water loss (TEWL) and erythema. After 7 days, statistically significant lower values of TEWL and erythema were found in corticosteroid-treated, compared to the vehicle-treated, skin reactions. The results indicate that topical corticosteroids improve healing of ICD.

The modulation of skin irritation

Irritant contact dermatitis (ICD) is a multifactorial disease, the onset and modulation of which depend on both endogenous and exogenous factors. Among the former, age, race, site, sex and history of dermatitis may all be important. Such variables can now readily be quantified by objective noninvasive techniques, such as measurement of transepidermal water loss (TEWL). Moreover, effects of irritants on the epidermis are related to the particular chemical properties of each molecule, contributing further to clinical heterogeneity. Release of cytokines and mediators may be initiated by a number of cells, including living keratinocytes and those of the stratum corneum, thus modulating inflammation and repair. Furthermore, differences in mechanisms of inflammation between acute and chronic ICD may exist, the former being characterized predominantly by inflammation, the latter by hyperproliferation and transient hyperkeratosis. These findings may explain the complexity and difficulty of investigating ICD. Better understanding and quantification of these mechanisms may lead to identification of high-risk individuals and more effective prevention and treatment.

The irritant effect of different metalworking fluids

The irritant effect of different water-based cutting fluids (CFs) on the skin was investigated in healthy subjects (n = 10) using 2 non-invasive bioengineering methods. Transepidermal water loss (TEWL) was measured by an evaporimeter EP1 (Servo Med), skin blood flow (SBF) was recorded with a laser Doppler flowmeter (MBF 3D, Moor Instruments England). Additionally all test sites were evaluated by visual scoring before measurement. 3 cutting fluids A, B and C from different manufacturers were tested at use concentrations of 4% or 5%. Single 24-h patch tests and repeated patch tests were performed on the volar side of the right forearm. Measurements were carried out before and after exposure to assess basal values and the skin response to CF. Tests with CFs A and C resulted in significant increase in TEWL after 24 h and after cumulative treatment, compared with controls (p < 0.01). The TEWL values for CF B did not differ from the water probe. An increase in SBF was found only for CFs A and C after cumulative patch testing (p < 0.01). In spite of their similar alkalinity, the 3 CFs showed different irritant skin reactions, due to their chemical components. This was verified particularly by measurement of TEWL.

Echographic evaluation with image analysis of irritant reactions induced by nonanoic acid and hydrochloric acid

Skin reactions to 40% nonanoic acid in propanol (NON) and to 4% hydrochloric acid were evaluated by image analysis of 20 MHz B scan recordings (Dermascan C, Cortex Technology). 18 women, aged 18 to 45, were patch tested with 24-h application time, and clinical and instrumental evaluations were performed at the beginning of the experiment, and 24 and 48 h after patch testing. To check possible regional variations in reactivity to NON and HCl, both substances were applied 2 x on the same forearm. As control tests, saline solution, propanol and sodium lauryl sulfate (SLS) 3% were applied. Echographic images were processed by a program enabling numerical representation of picture data, based on attribution of fictional values to the echoes' amplitudes, selection of amplitude bands of interest, binary transformation of the image, and calculation of the extension of areas reflecting within the same amplitude range. Sonographic recordings were evaluated by an amplitude interval marking hyporeflecting parts of the dermis (corresponding to edema and inflammatory infiltration), and by a band highlighting the entrance echo (epidermis). Our evaluations showed that extension of the hypoechogenic area of the dermis increases according to intensity of inflammatory reaction for all irritant substances. A clear decrease in reflectivity of the epidermis echo at 24 h was visible at SLS patch test test sites, whereas at patch test sites performed with NON and HCl, there was a trend towards an increase in values of hyperreflecting pixels. No significant variations between data recorded at proximal compared to distal skin sites were observed for NON and HCl. In conclusion, the echographic technique provides a method for quantification of the dermal inflammatory reaction, and also for description of skin reactions induced by irritant substances, according to their specific epidermal effects.

Site variations in patch test responses on the back

To establish the existence of intra-regional variations in response to allergens on the back, we performed patch tests in 21 patients at 2 different sites on the back. Visual readings using the numerical scale established by the International Contact Dermatitis Research Group were carried out 2 days after application of the allergen. After each visual reading, the skin blood flow at the test sites was quantified by laser Doppler flowmetry. The results of laser Doppler flowmetry showed a highly significant difference between the upper and lower back. It is therefore necessary that in quantitative and comparative investigations, symmetrical sites, i.e., left versus right sides of the body, should be studied.

Study of cumulative irritant contact dermatitis in man utilizing open application on subclinically irritated skin

We evaluated the effect of subclinical irritation on the cutaneous reaction elicited by cumulative short-term (30-min) application of sodium lauryl sulphate (SLS), by measuring transepidermal water loss (TEWL) and assigning visual scores. 11 healthy adult volunteers, free of skin disease and with no history of atopic dermatitis, were treated with SLS solution (1%, 2%, 5%, 7.5%). On a Monday, we applied 80 microliters of 1% SLS solution and deionized water (control), using large aluminium chambers with filter paper discs, for 30 min. We measured TEWL values 2 x before and after patch application of control and 1% SLS solution, and then applied 80 microliters of SLS solution (2%, 5%, 7.5%) using filter paper discs. From Tuesday to Friday, we applied 80 microliters of each solution, using filter paper discs, and measured TEWL before and after open application of test solutions. Compared with each corresponding group, TEWL values of SLS patch groups (S-2.0, S-5.0, S-7.5) were higher than those of water patch groups (W-2.0, W-5.0, W-7.5), respectively. TEWL values of each groups increased stepwise and the final (hour 97) TEWL values were higher than those of baseline (hour 0) TEWL. The mean visual scores of the vehicle control were lower than those of other test groups, but there were no statistically significant differences in visual scores between each test group. These findings suggested that impaired skin barrier function, elicited by subclinical irritation from short-duration contact with some irritants, might augment the cumulative irritant contact dermatitis caused by repeated open exposure to other surfactants.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of surfactant mixtures on irritant contact dermatitis potential in man: sodium lauroyl glutamate and sodium lauryl sulphate

Our purpose was to ascertain the irritant contact dermatitis potential of sodium lauroyl glutamate (SLG) and to assess its possible anti-irritating potential in a surfactant mixture on human skin, using visual scores and measurement of transepidermal water loss (TEWL). 15 healthy adult volunteers free of skin disease and with no history of atopic dermatitis were treated with sodium lauryl sulphate (SLS) solution (1%, 0.75%, 0.50%, 0.25%), 1% SLG solution, and 1% surfactant mixture solutions, M1 (75/25), M2 (50/50), M3 (25/50) (SLG/SLS). We applied 100 microliters of solution using a polypropylene chamber for 24 h. Application sites for each solution were randomized to minimize anatomical bias. We measured baseline TEWL before test solution application. After removal of the patches, each site was visually graded and TEWL recorded with an evaporimeter daily for 4 days. The visual scores and TEWL values of 1% SLG solutions were lower than those of the other test solutions, except the vehicle control (deionized water). 1% surfactant mixture solutions showed lower visual scores and TEWL values than 1% SLS solution. Increase of SLG concentration decreased the visual scores and TEWL values. Comparing the visual scores and TEWL values of M1 and 0.25% SLS solution, M2 and 0.50% SLS solution, and M3 and 0.75% SLS solution, M1, M2, and M3 showed lower values, although not statistically different. These findings suggest that SLG is a mild surfactant and its utilization can decrease irritation potential in SLS and possibly other mixtures. This model may offer a facile system for screening the surfactant and other mixtures for decreased irritancy potential.

Hydration, transepidermal water loss, pH and skin surface parameters: correlations and variations between dominant and non-dominant forearms

The aim of this study was to examine differences between the skin of both forearms with regard to several parameters: hydration (skin capacitance), transepidermal water loss (TEWL), pH and skin surface parameters. Possible correlations between measurements were investigated. Thirty-three healthy women (32.6 +/- 8.4 years) participated in the study. The different parameters were measured on each volar forearm (dominant and non-dominant) at precisely delineated sites. TEWL and developed length (DL) were significantly increased on the dominant forearm (P < 0.001 and P < 0.01, respectively). In addition, a correlation matrix was calculated with the differences between dominant and non-dominant forearms for all the parameters measured. Only the skin surface parameters were found to be interrelated with this statistical approach. These data confirm that randomization between forearms is essential in the design of a reliable experimental plan, and indicate the lack of relationship between these measurements as assessed in a group of healthy young women.

Barrier function parameters in various keratinization disorders: transepidermal water loss and vascular response to hexyl nicotinate

In this study, we characterized the stratum corneum barrier function in 39 patients with various keratinization disorders (autosomal dominant ichthyosis vulgaris [ADI] [n = 7], X-linked recessive ichthyosis [XRI] [n = 6], autosomal recessive congenital ichthyosis [CI] [n = 10], dyskeratosis follicularis [Darier's disease; DD] [n = 8], erythrokeratoderma variabilis [EKV] [n = 8]), and 21 healthy volunteers, using two non-invasive methods: transepidermal water loss (TEWL) measuring outward transport of water through the skin by evaporimetry, and the vascular response to hexyl nicotinate (HN) penetration into the skin as determined by laser-Doppler flowmetry. Significantly increased TEWL values were found on the volar forearm in all three forms of ichthyosis, compared with the healthy control group, with the highest TEWL values in the CI group. The penetration of HN on the volar forearm was accelerated in patients with ADI, XRI and CI, as indicated by a shorter lag time (t0) between HN application and initial vascular response. However, differentiation between CI and the other ichthyoses was not possible by this method. When using both methods in DD and EKV, no differences compared with the healthy controls could be detected on the volar forearm, where the skin was principally unaffected; only the measurements from the affected skin on alternative sites demonstrated significantly increased TEWL values. In ADI and CI, however, normal-appearing skin also showed impaired values. We conclude that both TEWL and the vascular response to penetration of HN are suitable methods to monitor the skin barrier function in keratinization disorders, and are helpful in discriminating between these disorders.

An arm immersion model of compromised skin (I). Influence on irritation reactions

Patch testing and safety evaluation processes to assess the allergic or irritant potential of substances are usually performed on normal skin. However, the reactivity of compromised skin may be different. Consequently, it is important to have a test procedure which acts as a model for compromised skin and which reproduces on the target sites the cumulative insult which results from repeated exposure, working temperatures, hydration and the action of surfactants. The procedure described uses regular immersion of forearm skin in an aqueous solution of sodium dodecyl sulphate until an identifiable alteration of skin condition is produced. In this first report, the model system has been described in detail and the influence of skin compromise on the response to 3 irritants, citral, sodium dodecyl sulphate and nonanoic acid, has been assessed. The irritation potential of the materials varied, but each irritant produced a greater degree of reaction on skin compromised to be within the normal clinical range one might expect from housework.

Skin barrier function in healthy volunteers as assessed by transepidermal water loss and vascular response to hexyl nicotinate: intra- and inter-individual variability

This study assesses the variability of two non-invasive methods of measuring stratum corneum barrier function in vivo. Transepidermal water loss (TEWL), and the vascular response to hexyl nicotinate (HN) penetration as determined by laser-Doppler flowmetry, were measured in a group of 21 healthy volunteers. Each time profile of the vascular response to HN penetration was analysed using the following parameters: the baseline cutaneous blood flow, the lag-time between application and initial response (t0), the time between application and maximum response (tmax), the maximum response, and the slope of the curve. TEWL measured on the left volar forearm showed a normal range of 3.9-7.6 g/m2h and a small inter-individual variability [coefficient of variation (CV) 19.4%]. TEWL values at three other forearm sites did not show differences of clinical importance compared with the left volar forearm. The parameters of the vascular response to HN penetration spanned a wider normal range than the TEWL values (CV between 33 and 52%). Repeat measurements after a 1-2 month interval showed highly reproducible individual TEWL values. The mean difference between first and second measurements was only 0.03 g/m2h; the relative difference 0.6%. The intra-individual reproducibility of t0 and tmax. for HN penetration was also high (relative differences of 2.8 and 3.1%, respectively). The other vascular response parameters were less reproducible (relative differences of 6.9-18.6%). We conclude that TEWL and selected parameters of HN penetration, as non-invasive tests of the stratum corneum barrier function, yield reproducible results and are hence useful for investigations assessing the skin barrier function in various disorders.

Fate and effects of the surfactant sodium dodecyl sulfate

Sodium dodecyl sulfate is the most widely used of the anionic alkyl sulfate surfactants. Its surface-active properties make it important in hundreds of household and industrial cleaners, personal care products, and cosmetics. It is also used in several types of industrial manufacturing processes, as a delivery aid in pharmaceuticals, and in biochemical research involving electrophoresis. SDS synthesis is a relatively simple process involving the sulfation of 1-dodecanol followed by neutralization with a cation source. Purification is accomplished through repeated extraction. It is available commercially in both broad-cut and purified forms. Although its environmental occurrence arises mainly from its presence in complex domestic and industrial effluents, SDS is also directly released in some applications (e.g., oil dispersants and pesticides). Although surfactants are known to significantly contribute to the toxicity of some effluents, no official water quality standards currently exist. Research has shown SDS to be highly biodegradable by a large number of naturally occurring bacteria, and degradation is generally reported to be > or = 90% within 24 hr. The process involves initial enzymatic sulfate liberation and conversion to dodecanoic acid, followed by either beta-oxidative shortening or elongation and desaturation. All surfactant properties are lost after initial sulfate hydrolysis. SDS can enhance absorption of chemicals through skin, gastrointestinal mucosa, and other mucous membranes. Thus, it is used in transepidermal, nasal, and ocular drug delivery systems and to enhance the intestinal absorption of poorly absorbed drugs; enhancement is concentration dependent. Human exposure is mainly through oral ingestion and dermal contact, although cases of respiratory exposure are known. The main sources of daily intake are ingestion of personal care products, residues on insufficiently rinsed utensils, and contaminated drinking water. Uptake, distribution, and excretion of SDS are all rapid. In fish, uptake in various tissues plateaus within 24-72 hr, with elimination occurring within < 24-48 hr; selective accumulation occurs in the hepatopancreas and gall bladder. In mammals, it is readily absorbed via the intestine, colon, and skin. Metabolism is similar in fish and mammals, proceeding from initial omega-oxidation to a carboxylic acid, then to beta-oxidation to butyric acid 4-sulfate, which is finally nonenzymatically desulfurated to gamma-butyrolactone and inorganic sulfate. SDS elicits both physical and biochemical effects on cells, with the membrane the primary target structure. Effects are concentration dependent and range from loss of barrier function and increased permeability to complete cell lysis. Hemolysis in mammals is pH dependent.(ABSTRACT TRUNCATED AT 400 WORDS)

Cutaneous reactivity to allergens at 24-h increases from the antecubital fossa to the wrist: an echographic evaluation by means of a new image analysis system

To establish the existence of regional variations in response to allergens, we performed patch tests with nickel sulfate 5% pet. at 4 different sites on the volar forearm skin in 17 nickel-sensitive women, aged from 18 to 45 years. After a 24-h application, patch tests were removed and evaluated both by clinical scoring and by means of a 20 MHz ultrasound B scanner. Recorded echographic images referring to uninvolved skin and to positive test sites were evaluated by a traditional image analysis method for the determination of skin thickness. Furthermore, they were processed by software which ascribes arbitrary values to the amplitude levels of the echoes and enables quantification of the pixels, (the smallest elements in a visual display with controllable colour and brightness) forming objects reflecting within a selected amplitude band. Thus, we demonstrated an increase in thickness of uninvolved skin at distal sites and a greater reactivity at 24 h to patch tests in skin areas near to the wrist crease, as evidenced by a greater increase in pixel and in thickness values at distal sites. From our data, we have a clear indication for the use of rotating patterns or symmetrical sites in quantitative and comparative investigations concerning the evaluation of contact allergy on volar forearm skin.

Skin irritation induced by topically applied timolol

1. Erythema induced by topically applied timolol, a non-selective beta-adrenoceptor blocker, was assessed in six male volunteers. Intensity of erythema developed on the inner surface of the left forearm where timolol free base was applied for 10 h was measured by a visual score, laser doppler flowmeter and reflectance spectrophotometry. Plasma timolol concentrations collected from the left and right arms were also measured. 2. The mean values for blood volume and blood flow per unit volume of tissue both of which were assessed by a laser doppler flowmeter, haemoglobin index measured by reflectance spectrophotometry, and magnitude of erythema graded by a visual score significantly increased after the application of an acrylic co-polymer adhesive patch containing 20% (w/v) timolol free base. 3. Plasma timolol concentrations collected from the left antecubital vein were 2.4 to 10.7 times greater than those from the right arm and had significant correlations (rs = 0.55 to 0.76) with the parameters indicating the extent of erythema developed where a patch containing timolol was applied. 4. The inter-individual variation of timolol was attributed to that of the diffusivity of timolol through skin rather than that of the skin reactivity to topically applied timolol because the plasma timolol concentrations drawn from the left arm in the subjects who did not develop erythema were very low.(ABSTRACT TRUNCATED AT 250 WORDS)