Short-term penetration of lanolin into human stratum corneum

E. W. Clark

226 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS removed visibly decreased as a function of depth, as would be expected from the other results. A secondary observation arising from the work was that test sites treated with lanolin prior to tape stripping healed significantly more quickly than untreated sites. This observation is being investigated further in a follow-up study. REFERENCES (1) G. Imokawa and M. Hattori, A possible function of structural lipids in the water-holding properties of the stratum corneum, J. Invest. Dermatol., 84, 282-284 (1985). (2) G. Imokawa, S. Akasaki, A. Kawamata, S. Yano, and N. Takaishi, Water-retaining functions in the stratum corneum and its recovery properties by synthetic pseudoceramides, J. Soc. Cosmet. ½hem., 40, 273-285 (1989). (3) A. J. I. Ward and C. du Reau, Modelling the permeability properties of skin, Cosmet. Toiletr., 105, 53-59 (1990). (4) E. W. Clark, New concepts of lanolin. In-Cosmetics Seminar, Birmingham NEC, England (March 1990). (5) E. W. Clark, Estimation of the general incidence of specific lanolin allergy,J. $oc. Cosmet. Chem., 26, 323-335 (1975). (6) E. W. Clark, E. Cronin, and D. S. Wilkinson, Lanolin with reduced sensitizing potential, Contact Dermatitis, 3, 69-74 (1977). (7) H. Ippen, Investigations on contact allergy to woolwax. 5th session of the International Contact Dermatitis Group, Barcelona (1980). (8) E. W. Clark, A. Blondeel, E. Cronin, J. A. Oleffe, and D. S. Wilkinson, Lanolin of reduced sensitizing potential, Contact Dermatitis, 7, 80-83 (1981). (9) B. Edman and H. Moeller, Testing a purified lanolin preparation by a randomized procedure, Contact Dermatitis, 20, 287-290 (1989). (10) K. Okamoto, Studies on the quantity and chemical composition of surface lipids of human scalp and hair, J. Dermatol, (Tokyo), 7, 85-99 (1985). (11) E. V. Truter, Wool Wax Chemistry and Technology (Cleaver-Hume Press Limited, London, 1956), p. 185. (12) C. S. King, S. P. Barton, S. Nicholls, and R. Marks, The change in properties of the stratum corneum as a function of depth, Brit. J. Dermatol., 100, 165-172 (1979). Appendix I: DERIVATION OF A CALIBRATION CURVE FOR THE SPECTROPHOTOMETRIC DETERMINATION OF LANOLIN MATERIALS AND EQUIPMENT ß Chloroform AR ß Acetic anhydride AR ß Sulphuric acid, concentrated AR ß Anhydrous lanolin BP (Westbrook) ß 50-ml graduated burette ß 50-ml graduated stoppered glass cylinders ß 1-ml graduated pipette ß Optical glass cells, 20-mm path length ß Spectrophotometer, Philips PU 8650 PROCEDURE A standard solution of lanolin in chloroform was prepared with a concentration of 0.37 gl-•. Eight different measured volumes of this standard solution were run from the

PENETRATION OF LANOLIN 227 burette into a 50-ml graduated cylinder and made up to 13.5 ml (if necessary) with chloroform, then up to a total of 25.0 ml with acetic anhydride. To avoid buretting volumes less than i ml, the standard solution when appropriate was diluted 10-fold volumetrically with chloroform to a concentration of 0.037 gl-•. To each prepared mixture of standard lanolin solution and acetic anhydride was added 0.5 ml of concen- trated sulphuric acid by pipette, and the mixture was shaken and transferred to an optical cell. A blank was prepared similarly but using chloroform only, without lanolin, and used for comparison, the absorbance being measured at 458 nm and 25øC at frequent intervals. Absorbance reached a maximum after about 15 to 20 minutes, then began slowly to fall. The maximum reading was regarded as definitive. The total of eight readings obtained was plotted as a calibration curve (Figure 3), which followed the classical Beer-Lambert form. The sensitivity in the linear region of the graph is 1.25 mg lanolin per unit absorbance.

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