Preventing irritant contact dermatitis with protective creams: influence of the application dose

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1 Contact Dermatitis Original Article COD Contact Dermatitis Preventing irritant contact dermatitis with protective creams: influence of the application dose Sibylle Schliemann, Maximilian Petri and Peter Elsner Department of Dermatology, University Hospital Jena, D Jena, Germany doi: /cod Summary Background. Skin protection creams (PC)s are used in the occupational setting to help prevent irritant hand dermatitis. The actual amounts of PC applied and the resulting dose per unit area on hands at work are lower than recommended. Objectives. To assess the influence of the applied dose on the efficacy of PCs in the prevention of irritant contact dermatitis. Methods. Experimental cumulative irritant contact dermatitis was induced by twice daily application of 0.5% NaOH or sodium lauryl sulfate (SLS) for 4 days on the backs of 20 healthy volunteers. Test areas were left unprotected or were pretreated with three differentpcsappliedatalowdose(2 mg/cm 2 )orahighdose(20 mg/cm 2 )beforeirritation. Irritant responses were assessed by visual scoring and measurement of transepidermal water loss, chromametry, and corneometry. Results. Although cumulative irritant dermatitis developed in all unprotected test sites, irritation was significantly reduced in a dose-dependent manner on PC-protected sites. The higher doses of all PCs provided significant protection against irritation. However, the lower dose of one product did not significantly protect against SLS-induced irritation. Conclusions. The protective efficacy of PCs depends on the amount of product applied per unit skin surface area. Some products may show no protective efficacy when used at doses close to those practically applied at workplaces. Future efficacy studies of PCs should be performed with doses not higher than 2 mg/cm 2, to avoid overestimation of their protective efficacy. Key words: barrier cream; cumulative irritation; efficacy; occupational dermatitis; prevention; quantity; skin protection cream. Skin protection creams (PCs) are widely used in workplaces to diminish the impact of harmful chemicals on the epidermal skin barrier and to help prevent cumulative irritant dermatitis. Studies assessing the efficacy of PCs have shown divergent results: Whereas some studies confirmed efficacy claims (1), others showed Correspondence: Sibylle Schliemann, Department of Dermatology, University Hospital Jena, Erfurter Str. 35, D07743 Jena, Germany. Tel: ; Fax: schliemann@derma-jena.de Conflicts of interest: The authors have declared no conflicts. Accepted for publication 17 April 2013 that PCs may be without effect or even aggravate the irritation instead of protecting against it (2, 3). One reason for the divergent results may be the heterogeneity of PC application in these studies. When we analysed the quantities of PCs per unit area of skin surface applied in published studies, we were surprised to note that a wide range of doses, from 4 to 25 mg product/cm 2 skin, has been used over the years (4). We therefore studied the amounts of PC applied by hospital nurses under routine working conditions, and found that the population studied applied slightly less than 1 mg product/cm 2 (4). This dose is significantly lower than the amounts that have been used in experimental efficacy studies. Contact Dermatitis, 70,

2 With these new data in mind, it seemed necessary to assess the dependence of the efficacy of PCs in preventing cumulative irritant contact dermatitis on the amounts actually applied on the skin. Materials and Methods Study design The study was conducted as a single-blind, randomized, controlled, single-centre clinical trial in September and October Subjects Fifteen female and 5 male healthy Caucasian volunteers, aged years, participated in the study. Volunteers were included after receipt of a written informed consent declaration. Further inclusion criteria were age between 18 and 55 years, a test area on the back without any signs of irritation, tattoos or intense hair growth, abstaining from the use of cosmetics on the back for at least 1 week preceding the study, and abstaining from showering or bathing and ultraviolet (UV) exposure during the study. Exclusion criteria were a history of or present skin diseases, internal or neurological diseases, UV exposure of the back during the 4 weeks preceding the study, known sensitization against cosmetic ingredients, use of systemic antihistamines, immunosuppressives or any other drug that could possibly interfere with the study, and pregnancy or breast-feeding for women. The study was approved by the ethics committee of University Hospital Jena (Vote No /08). Chemicals and protective creams Sodium lauryl sulfate (SLS) (CAS no , Fa. ROTH, Karlsruhe, Germany, 99.5%) and NaOH (CAS no , Fa. ROTH, Karlsruhe, Germany, 99%) were used as model irritants in a 0.5% aqueous solution. Three commercial PCs that were claimed to protect against hydrophilic workplace irritants were used to study dose-dependent efficacy. Samples of the products were bought on the German market at the time of the study: Product A ( Protection against hydrophilic and formaldehyde-containing workplace substances ) had the following ingredients according to INCI: aqua, paraffinum liquidum, urea, petrolatum, cera alba, cholesterol, zinc stearate, sodium stearate, lanolin alcohol, aluminium chlorohydrate, and parfum (fragrance). Product B ( Protection against hydrophilic workplace substances ) had the following ingredients according to INCI: aqua, petrolatum, ethylhexyl stearate, paraffinum liquidum, polyglyceryl-2-dipolyhydroxystearate, cetearyl isononanoate, glycerin, aprylic/capric triglyceride, cera alba, magnesium sulfate, zinc stearate, tocopheryl acetate, hydrogenated castor oil, parfum, phenoxyethanol, methylparaben, ethylparaben, butylparaben, propylparaben, and isobutylparaben. Product C ( Protecting the skin from direct contact with water-mixed oils and metalworking fluids, acids, bases, salts, alcoholic solutions and disinfectants ) had the following ingredients according to INCI: aqua, kaolin, paraffinum liquidum, paraffin, cetearyl alcohol, cetyl alcohol, petrolatum, zinc oxide, sodium hexametaphosphate, SLS, sodium cetearyl sulfate, methylparaben, and CI Study procedures and measurements After informed consent had been received, and volunteers had been included on the basis of inclusion and exclusion criteria, 13 test areas were marked on the backs of the participants according to a permuting randomization plan. The test areas were 18 mm in diameter, and were located paravertebrally at a distance of 10 cm from the median line. Twice daily, a standardized amount of products A C (5 or 50 μl) was applied on the test fields, and spread evenly without pressure with a glove-protected finger. Related to the diameter of 18 mm and according to weight/volume measurements, the volume of 5 μl approximated to a dose of 2 mg/cm 2 test area, and the volume of 50 μl approximated to a dose of 20 mg/cm 2 for all products. Volume-related application with Eppendorf pipettes was chosen in order to avoid laborious and less exact weighing procedures. The application areas were left open for 10 min. Then, 50 μl of the 0.5% hydrophilic irritant solution (NaOH for products A and C, and SLS and for products A C) was applied according to a randomization plan. The irritants were pipetted onto filter paper discs in large Finn Chambers (12 mm; Epitest Ltd Oy, Tuusula, Finland, distributed by Smart Practice Germany GmbH, Barsbuettel, Germany). The Finn Chambers were fixed in the centres of the 18-mm test fields with occlusive tape. After 30 min, the test chambers were removed, and the test areas were allowed to dry. The test areas were as follows: Test area 1: untreated control area (negative control). Test area 2: 0.5% SLS (positive control SLS). Test area 3: 0.5% NaOH (positive control NaOH). Test area 4: 5 μl of product A, irritation with SLS. Test area 5: 50 μl of product A, irritation with SLS. Test area 6: 5 μl of product A, irritation with NaOH. 20 Contact Dermatitis, 70, 19 26

3 Fig. 1. Influence of skin protection cream (PC) dose on NaOH-induced cumulative irritation (product A): mean difference from baseline (day 4 to day 0) for visual scores (sum score), transepidermal water loss (TEWL) and chromametric a* and corneometer values for test areas treated with product A (5 μl versus 50 μl applied per test area). Positive control: irritated field (NaOH) without PC. Negative control: untreated field. Error bars indicate 95% confidence intervals. AU, arbitrary units. Test area 7: 50 μl of product A, irritation with NaOH. Test area 8: 5 μl of product B, irritation with SLS. Test area 9: 50 μl of product B, irritation with SLS. Test area 10: 5 μl of product C, irritation with SLS. Test area 11: 50 μl of product C, irritation with SLS. Test area 12: 5 μl of product C, irritation with NaOH. Test area 13: 50 μl of product C, irritation with NaOH. Product B was not tested against NaOH, because of the limited number of test areas available. Between measurements and applications, the test areas were only covered by clothing and kept dry. Measurements and clinical scoring Prior to visual scoring and the measurements, volunteers acclimatized themselves for at least 20 min to the standardized laboratory conditions (temperature C, humidity 30 40%). Measurements and clinical scoring were performed by the same investigator (M.P.) from day 0 to day 3 before application of the PCs and irritants. On day 4, the last day of the study, only the skin physiology measurements were performed, and the clinical irritation score was taken. Clinical assessment was based on visual clinical scoring according to the European Society of Contact Dermatitis guideline on clinical scoring of acute SLS irritant reactions (5). Transepidermal water loss (TEWL) (expressed in g/m 2 /h) as an indicator of epidermal barrier function was measured with a TM 310/MPA9 Tewameter (Courage & Khazaka Electronic GmbH, Cologne, Germany), according to the guidelines of Pinnagoda et al. (6, 7) and Rougier et al. (8). Contact Dermatitis, 70,

4 Fig. 2. Influence of skin protection cream (PC) dose on NaOH-induced cumulative irritation (product C): mean difference from baseline (day 4 to day 0) for visual scores (sum score), transepidermal water loss (TEWL) and chromametric a* and corneometer values for test areas treated with product C (5 μl versus 50 μl applied per test area). Positive control: irritated field (NaOH) without PC. Negative control: untreated field. Error bars indicate 95% confidence intervals. AU, arbitrary units. The intensity of erythema was quantified with a CR-300 Chromameter (Minolta GmbH, Ahrensburg, Germany), according to the published guideline (9). Only the a*-score, which represents the red green axis of the three-dimensional assay system, was considered, with higher a*-values for more intense redness. Skin hydration state was measured with a CM- 825/MPA9 Corneometer (Courage & Khazaka), as described by O goshi and Serup (10). On each test area, three repeated measurements were performed, and the mean of the measured hydration values was calculated. Data analysis and statistics The data were statistically analysed with spss (Version 19 for Windows ; IBM, Armonk, NY, USA). Testing for difference between measurement values on test areas at day 0 and day 4 was performed with the non-parametric Wilcoxon test, adjusted for multiple testing with the Bonferroni Holm correction. Results NaOH irritation For product A, visual score, TEWL and chromametry showed a significant increase for the test areas treated with the low dose (5 μl) under irritation by NaOH from day 0 to day 4. The stratum corneum hydration showed a significant decline with the low dose, whereas there were no significant changes in the areas treated with 50 μl. However, the values in the areas protected with the 22 Contact Dermatitis, 70, 19 26

5 Fig. 3. Influence of skin protection cream (PC) dose on sodium lauryl sulfate (SLS)-induced cumulative irritation (product A): mean difference from baseline (day 4 to day 0) for visual scores (sum score), transepidermal water loss (TEWL) and chromametric a* and corneometer values for test areas treated with product C (5 μl versus 50 μl applied per test area). Positive control: irritated field (SLS) without PC. Negative control: untreated field. Error bars indicate 95% confidence intervals. AU, arbitrary units. low dose were still significantly lower than those for the positive controls (Fig. 1). For product C, visual score, TEWL and chromametry showed a significant increase for the test areas treated with the low dose (5 μl) and those treated with the high dose (50 μl) under irritation by NaOH from day 0 to day 4. The stratum corneum hydration showed a significant decline with both doses. There were no significant differences between the test areas treated with the different doses, and both showed a significantly lower degree of irritation than the unprotected positive controls (Fig. 2). SLS irritation For product A, visual score, TEWL and chromametry showed a significant increase for the test areas treated with the low dose (5 μl) under irritation by SLS from day 0 to day 4, whereas there were no significant changes in the areas treated with 50 μl. However, the areas protected with the low dose showed significantly less changes in irritation than the positive controls. The stratum corneum hydration showed a significant decline with the low dose, whereas there was no significant difference from the negative control for the high dose (Fig. 3). For product B, visual score, TEWL and chromametry showed a significant increase for the test areas treated with the low dose (5 μl) under irritation by SLS from day 0 to day 4, whereas there were no significant changes in the areas treated with 50 μl. The stratum corneum hydration showed a significant decline with the lower dose. The values in the areas protected with the low dose did not Contact Dermatitis, 70,

6 Fig. 4. Influence of skin protection cream (PC) dose on sodium lauryl sulfate (SLS)-induced cumulative irritation (product B). Mean difference from baseline (day 4 to day 0) for visual scores (sum score), transepidermal water loss (TEWL) and chromametric a* and corneometer values for test areas treated with product C (5 μl versus 50 μl applied per test area). Positive control: irritated field (SLS) without PC. Negative control: untreated field. Error bars indicate 95% confidence intervals. AU, arbitrary units. differ significantly from those for the positive controls, indicating insufficient protection (Fig. 4). For product C, visual scoring and TEWL showed a significant increase for the test areas treated with the low dose (5 μl) under irritation by SLS from day 0 to day 4. Chromametry also showed an increase with the low dose, but it was not significant. Corneometry showed a significant decline for the test areas treated with the low dose. In visual scoring, TEWL, and chromametry, the values for the area treated with both doses still remained significantly below that of the positive irritant control, thus indicating some protection. However, the corneometer values indicating stratum corneum hydration were even lower than those for the positive control for the low dose, without reaching significance (Fig. 5). Discussion For most of the PCs and the irritants tested, we found that the degree of protection against cumulative irritation depended on the dose of the product applied on the test area. Product A completely prevented NaOH-induced and SLS-induced irritation when applied at a dose of 20 mg/cm 2, whereas the lower dose of 2 mg/cm 2 still significantly reduced the irritation. In contrast, for product B, there was highly significant protection against SLS irritation by the high dose, whereas the low dose provided no significant protection. Product C showed significant protection against NaOH by both doses, but the protection efficacy between the doses was not significantly different. For SLS, there was again a significant difference between the doses, with the high dose showing no 24 Contact Dermatitis, 70, 19 26

7 Fig. 5. Influence of skin protection cream (PC) dose on sodium lauryl sulfate (SLS)-induced cumulative irritation (product C): mean difference from baseline (day 4 to day 0) for visual scores (sum score), transepidermal water loss (TEWL) and chromametric a* and corneometer values for test areas treated with product C (5 μl versus 50 μl applied per test area). Positive control: irritated field (SLS) without PC. Negative control: untreated field. Error bars indicate 95% confidence intervals. AU, arbitrary units. significant difference from the negative, untreated control, and the low dose showing less, but still significant, protection, except for the stratum corneum hydration. The dose effect relationship of protective creams may thus differ between products. This underscores the need to consider adequate dosing for efficacy studies. As mentioned above, previous efficacy studies used doses between 4 and 25 mg product/cm 2 skin. Considering our results and the fact that the dose practically applied at the workplace is slightly less than 1 mg product/cm 2 (4), it is obvious that the doses used in efficacy studies in the past were unrealistically high, and probably led to an overestimation of the efficacy of some PCs (e.g. product B in our study). It might be argued that the lower dose of 2 mg product/cm 2 used in the present study still exceeds the dose practically applied in the workplace determined in our previous study (4). However, dosing of small test areas is limited by the minimum amount of substance that can still be handled and spread with sufficient precision. This dose cannot be reduced to < 2 mg product/cm 2 without risking a reduction in the quality and thus poor reproducibility of data. This is also the reason why COLIPA (now Cosmetics Europe) uses 2 mg product/cm 2 for assessment of the sun protection factor, stressing the fact that the amount of product applied and the uniformity of spreading on the test sites affects the magnitude and variability of the test results (11). For these practical reasons, we therefore recommend using a test dose of not less than 2 mg product/cm 2 in future PC efficacy studies. In this study, our focus was merely on investigating a roughly realistic dose of marketed PCs as compared with Contact Dermatitis, 70,

8 the 10-fold higher doses that have been preferred in the majority of published experimental studies (12 15). To our knowledge, such low quantities per unit skin area have never been implemented in an experimental in vivo efficacy model before. Nevertheless, we were able to show protective efficacy, at least for some products. However, at this point, it is still not possible to clarify the mechanisms of action of the respective products. Moreover, the mechanisms of PC action are still inadequately understood (16), which is dissatisfying. Possible mechanisms that have been discussed include the formation of a physical barrier on the stratum corneum that prevents or diminishes the penetration of irritants. Some skin models provide clear evidence of such effects (14, 17). In addition, barrier strengthening and restoration may be induced, as has been demonstrated for moisturizers(18 20). Presumably, the action of a given PC may be the result of a variable combination of barrier shielding and effects on physiological barrier strengthening, for example stimulation of barrier repair, the details of which may depend on the specific preparation. Currently, we do not have any suitable methods available to differentiate or actually rate the different proportions of both effects in one model. Therefore, further efforts are needed to improve in vivo efficacy models for PCs and to gain better insights into the effects. Considering the dose effect relationship of PCs observed in our study, special emphasis should be placed on training workers at irritation-prone workplaces to use sufficient amounts of PCs, as too low doses may be without preventive effect, even for products that have been shown to have preventive efficacy in experimental studies. Studies are needed to assess whether teaching interventions for workers at risk of irritant dermatitis may enhance the coverage of at-risk skin areas by PCs (21), and whether dosing can be elevated to levels with significant preventive potential. References 1 Wigger-Alberti W, Rougier A, Richard A, Elsner P. Efficacy of protective creams in a modified repeated irritation test. Methodological aspects. Acta Derm Venereol 1998: 78: Frosch P J, Schulze-Dirks A, Hoffmann M, Axthelm I. Efficacy of skin barrier creams (II). Ineffectiveness of a popular skin protector against various irritants in the repetitive irritation test in the guinea pig. Contact Dermatitis 1993: 29: Schluter-Wigger W, Elsner P. Efficacy of 4 commercially available protective creams in the repetitive irritation test (RIT). Contact Dermatitis 1996: 34: Schliemann S, Petri M, Elsner P. How much skin protection cream is actually applied in the workplace? Determination of dose per skin surface area in nurses. 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