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Appendix C Evaluations of Barrier Creamsi Howard I. Maibach and Hongbo Zhai IN VITRO DATA In vitro studies test the effects of barrier creams on the skin, which mimics the reaction of in viva skin. The in vitro method provides not only qualitative data (i.e., distinguishes between the creams) but also quantita- tive data (i.e., differences in absorption). Langford (1978) conducted in vitro studies to determine the behavior of a formulated fluorochemical- resin complex and a number of other solvents. He tested penetration through treated filter paper, repellency on treated pigskin, and penetra- tion of radio-labeled sodium lauryl sulfate through treated hairless mouse skin. The fluorochemical-resin complex provided the best resistance against a range of solvents. Reiner et al. (1982) studied the protective effect of model ointments on guinea pig skin in vitro. The permeation values of a toxic agent through unprotected and protected skin within 10 hours as a function of time were determined radiologically and enzymatically. Permeation of the toxic agent was markedly reduced by ointments with a polyethylene glycol base and ointments containing active substances. Loden (1986) evaluated the effects of barrier creams on the absorption of (l3H)-water (l4C)-benzene and (l4C)-formaldehyde by excised human 1The following material was prepared for the use of the principal investigators of this study. The opinions and conclusions herein are the authors' and not necessarily those of the National Research Council. 217
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218 STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES skin. The control skins and treated skins were exposed to the test sub- stance for 30 minutes, and the amount absorbed was determined. The model experimental "water barrier" cream reduced the absorption of water and benzene but not formaldehyde. Only one cream slightly re- duced the absorption of benzene and formaldehyde; the others did not. Fullerton and Menne (1995) tested the protective effect of ethylene- diaminetetraacetate barrier gels against nickel contact allergy in in vitro and in viva studies. In an in vitro study, about 30 mg of barrier gel was applied on the epidermal side of the skin and a nickel disc applied. After 24 hours, the disc was removed, the epidermis was separated from the dermis, and the nickel content in the epidermis and dermis was quanti- fied by adsorption differential pulse voltammetry. The amount of nickel in the epidermal skin layer on treated skins was significantly less than the amount in untreated skins. Zhai et al. (1999) used an in vitro diffusion system to measure the protective effect of quaternium-18 bentonite gels to prevent 1 percent concentration of [35S] sodium lauryl sulfate penetration in human cadaver skin. The accumulated amount in receptor cell fluid was mea- sured to evaluate the model gels over 24 hours. The test gels significantly decreased absorption when compared to the control samples of unpro- tected skin. Treffel et al. (1994) measured the effectiveness on human skin of barrier creams against dyes (eosin, methylviolet, and oil red O) with varying n-octanol/water partition coefficients (0.19, 29.8 and 165, respec- tively). Barrier cream effects were assayed by measuring the dyes in the epidermis of protected skin samples after 30 minutes. They found no correlation between the galenic (pharmaceutic) parameters of the assayed products and the protection level, indicating that neither the water con- tent nor the consistency of the formulations affected the level of protec- tion. This physicochemical data could be used for tailoring barrier creams to meet the challenges of specific chemical agents. IN VIVO DATA Mahmoud and Lachapelle (1985) and Lachapelle et al. (1990) used a guinea pig model to evaluate the protective value of barrier creams and/or gels by laser Doppler flowmetry (blood flow) and histological assess- ment. The histopathological damage after 10 minutes of contact to tolu- ene was mainly confined to the epidermis; the dermis was almost normal. Dermal blood flow changes were relatively high on the control site com- pared to the sites pretreated with gel. In addition, the blood concentra- tions of n-hexane in the control group and the gel-pretreated group were
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APPENDIX C 219 determined. It was possible to correlate results found by invasive (blood levels) and noninvasive techniques. Frosch et al. (1993a, 1993b, 1993c), and Frosch and Kurte (1994) devel- oped the repetitive irritation test in the guinea pig and in humans to evaluate barrier creams using a series bioengineering techniques. The pretreated and untreated test skin (guinea pig or human) was exposed daily to the irritants for two weeks. The resulting irritation was scored on a visual scale and assessed by biophysical (bioengineering) techniques. Some test creams suppressed irritation with all test parameters; some showed no effect, and even increased irritation. Zhai and Maibach (1996) used an in viva human model to measure the effectiveness of barrier creams against dye indicator solutions, methylene blue in water and oil red O in ethanol, representative of model hydrophilic and lipophilic compounds. Solutions of 5 percent methylene blue and 5 percent oil red O were applied to untreated and barrier-cream pre- treated skin with the aid of aluminum occlusive chambers, for either a few minutes or four hours. At the end of the application time, the materi- als were removed and consecutive skin surface biopsies were taken. The amount of dye that had penetrated into each strip was determined by calorimetry. Two model creams were effective; one increased the cumula- tive amount of dye. References Frosch, P.J., A. Kurte, and B. Pilz, 1993a. Efficacy of skin barrier creams. 3. The repetitive irritation test (RIT) in humans. Contact Dermatitis 29: 113-118. Frosch, P.J., A. Schultze-Dirks, M. Hoffmann, I. Axthelm, and A. Kurte. 1993b. Efficacy of skin barrier creams. 2. Ineffectiveness of a popular "skin protector" against various irritants in the repetitive irritation test in the guinea pig. Contact Dermatitis 29: 74-77. Frosch, P.J., A. Kurte, and B. Pilz. 1993c. Biophysical Techniques for the Evaluation of Skin Protective Creams. Pp. 214-222 in Noninvasive Methods for the Quantification of Skin Functions. P.J. Frosch and A.M. Kligman, eds. Berlin: Springer-Verlag. Frosch, P.J., and A. Kurte. 1994. Efficacy of skin barrier creams. 4. The repetitive irritation test (RIT) with a set of four standard irritants. Contact Dermatitis 31: 161-168. Fullerton, A., and T. Menne. 1995. In vitro and in vivo evaluation of the effect of barrier gels in nickel contact allergy. Contact Dermatitis 32: 100-106. Lachapelle J.M., H. Nouaigui, and L. Mavot. 1990. Experimental study of the effects of a new protective cream against skin irritation provoked by the organic solvents n-hexane, trichloethylene and toluene. Dermatosen Beruf Umwelt 38: 19-23. Langford, N.P. 1978. Fluorochemical resin complexes for use in solvent repellent hand creams. American Industrial Hygiene Association Journal 39: 33-40. Loden, M. 1986. The effect of four barrier creams on the absorption of water, benzene, and formaldehyde into excised human skin. Contact Dermatitis 14: 292-296. Mahmoud, G., and J.M. Lachapelle.1985. Evaluation of the protective value of an antisolvent gel by laser Doppler flowmetry and histology. Contact Dermatitis 13: 14-19.
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220 STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES Reiner, R., K. Rossmann, C.V. van Hooidonk, B.I. Cuelen, and J.Bock. 1982. Ointments for the protection against organophosphate poisoning. Arzneimittelforschung 32: 630-633. Treffel, P., B. Gabard, and R. Juch. 1994. Evaluation of barrier creams: an in vitro technique on human skin. Acta Dermatologica Venereolica 74: 7-11. Zhai, H., and H.I. Maibach. 1996. Effect of barrier creams: human skin in vivo. Contact Dermatitis 35: 92-96. Zhai, H., D.J. Buddrus, A.A. Schultz, R.C. Wester, T. Hartway, S. Serianzana, and H.I. Maibach. 1999. In vitro percutaneous absorption of sodium lauryl sulfate in human skin decreased by quaternium-18 bentonite gels. In Vitro Molecular Toxicology 12: 11-15.