182 JOURNAL OF COSMETIC SCIENCE basal permeability barrier function as is well established in the case of atopic dermatitis. This also explains the lack of a simple quantitative relationship between Malassezia species and D/SD presence or severity. Integrating all available data, it appears that dandruff and seborrheic dermatitis most likely results from three specific etiologic factors: 1 - Individual susceptibility 2 - Sebaceous secretion and 3 - Malassezia fungi. Individual susceptibility is most likely related to basal permeability barrier function, immune system function, and possibly even the overall microbial community. Treatment As D/SD are the result of sebum secretion, fungal activity, and innate susceptibility, the easiest, safest, and most effective treatments remain anti-fungal shampoos. The most common anti-fungal materials in use today are pyrithione zinc (ZPT), selenium sulfide (SexSy), ketoconazole, and to a lesser extent climbazole and octopirox. As rinse off products leave only small amounts of active material, in the microgram per square centimeter range, much caution must be taken with pharmacology. The deposition profile must be adequate for the materials potency, the residual material must be deposited in the appropriate location in a bioavailable manner, and the product must be cosmetically appealing enough for the patient to continue use. Several ZPT particles with differing deposition and bioavailability profiles will be discussed. Conclusions The common etiology ofD/SD is therefore a convergence of three factors: 1) SG secretions, which provide the substrate for Malassezia growth 2) Malassezia metabolism of the sebaceous secretions, releasing irritating unsaturated fatty acids and 3) individual susceptibility to the penetration of the fatty acids and the resultant inflammation. The optimal and most efficacious method for treatment is anti-fungal actives delivered from rinse-off products. The low deposition inherent in rinse-off products places significant constraints on the potency of the active material and the delivery pharmacology of the product chassis. References 1. Dawber, R: Diseases of the Hair and Scalp. London, Blackwell Science, 1997 p 499-504 2. McOsker, DE, Hannon, DP: Ultrstructural studies of dandruff-involved scalp tissue. The Toilet Goods Association 47: 5-8, 1967 3. Warner, RR Schwartz, JR Boissy, Y Dawson, TL: Dandruff has an altered stratum comeum ultrastructure that is improved with zinc pyrithione shampoo. J Am Acad Dermatol 45: 897-903, 2001 4. Gupta, AK Batra, R Bluhm, R Boekhout, T Dawson, TL: Skin diseases associated with Malassezia species. J Am Acad Dermatol Sl:785-98, 2004 5. Strauss, JS Pochi, PE: Histology, histochemistry, and electron microscopy of sebaceous glands in man. In: Gans, 0, Steigleder, GK (ed). Handbuch der Haut-und Geschlechtskrankheiten Normale und Pathologische Anatomie der Haut I. Berlin: Springer-Verlag, 1968 p 184-223 6. Strauss, JS Downing, DT Ebling, FJ: Sebaceous glands. In: Goldsmith, LA (ed). Biochemistry and Physiology of Skin. New York: Oxford University Press, 1983 p 569-595 7. Gupta, AK Bluhm. R Cooper, EA Summerbell, RC Batra, R: Seborrheic dermatitis. Dermatol Clin 21: 401-412, 2003 8. Malassez, L: Note Sur le Champignon du Pityriasis Simple. Arch. De Physiologie l: 451, 1874 9. Shuster, S: The aetiology of dandruff and the mode of action of therapeutic agents. Br J Dermatol l l l: 235- 42, 1984 10. Pierard-Franchimont, C, Hermanns, JF, Degreef, H, Pierard, GE: From axioms to new insights into dandruff. Dermatology 200: 93-8, 2000 11. Gueho, E, Boekhout, T, Ashbee, HR, Guillot, J, Van Bellcum A, Faergemann, J: The role of Malassezia species in the ecology of human skin and as pathogens. Med Mycol 36 Suppl 1 220-9, 1998 12. Guillot, J, Gueho, E: The diversity ofMalassezia yeasts confirmed by rRNA sequence and nuclear DNA comparisons. Antonie van Leeuwenhoek 67: 297-314, 1995 13. Gemmer, CM, DeAngelis, YM Theelen, B, Boekhout, T, Dawson, TL: Fast, Noninvasive Method for Molecular Detection and Differentiation of Malassezia Yeast Species on Human Skin and Application of the Method to Dandruff Microbiology. J Clin Microbiol 40: 3350-3357, 2002 14. DeAngelis, YM., Gemmer, CM, Kaczvinsky, JR, Kenneally, D, Schwartz, JR, and TL Dawson, Jr. (2005) 1bree etiologic facets of dandruff and seborrheic dermatitis: Malassezia fungi, Sebaceous lipids, and Individual sensitivity. J Invest Dermatol. (in press).

2005 ANNUAL SCIENTIFIC MEETING 183 HYDRATION EFFECT ON HUMAN NAIL PERMEABILITY Hemali Gunt and Gerald B. Kasting, Ph.D. College of Pharmacy, University of Cincinnati, Cincinnati, OH Statement of purpose: Onychomycosis is the #1 nail disorder diagnosed and treated by podiatrists and it accounts for up to 50% of nail diseases. Up to 13% of population of the United States is estimated to have dennatophyte onychomycosis. Over the years treatment of onychomycosis has changed from nail avulsion to pharmacotherapy with oral anti-fungals and nail lacquer. A desirable characteristic of a topical antifungal agent in the treabnent of onychomycosis is the ability of the drug to penetrate the keratin of the nail. However, topical treatment alone is generally unable to cure onychomycosis because of insufficient nail plate penetration. The effects of water on keratinized tissues, including horn, wool, hair and stratum comeum are studied to some extent, showing that the mechanical and transport properties are related to water content. While this infonnation is fundamental, literature review shows a paucity of data with respect to human nails. The magnitude of the effect observed in other tissues suggests that hydration may be an important determinate ofungual drug delivery, e.g., for topical treatment of nail dystrophies caused by onychomycosis, nail psoriasis and paronychia. The understanding and knowledge of hydration effects on nail permeability may be useful clinically and cosmetically in topical treabnent of nail disorders. The purpose of this study is to clearly define the effects of hydration on human nail permeability to water, i.e., to quantify transport parameters for water in human nail over a complete range of hydration. Method: We performed vapor phase water sorption-desorption studies at 32°C and 7 different water activities ranging from 15-100% using cadaver finger nails and tritiated water (3H2O) as a probe. Environmental relative humidity was controlled with various concentrations ofH2SO4, NaCl, K2CO3, and LiCl solutions. 1 Human nail samples (3 donors with n=2/donor) free of any adherent tissue were cleaned with a mild detergent solution and dried at 45°C. Dry human nail samples were allowed to sorb over (in vapor phase) tritiated water of radioactive concentration 10 µCi/ml. The nail tissue was weighed periodically to determine whether equilibrium was achieved. At the end of the sorption phase the nail samples were moved periodically over solutions (in vapor phase) with no radioactive compound and the rate of desorption of radioactivity from the nail was measured. Desorption was studied until no radioactivity was detected in the receptor solutions. The vapor phase assembly was replaced between the sorption to desorption phase to eliminate errors resulting from radioactive compound being trapped in the assembly. Radioactivity was measured using liquid scintillation counting. Figure 1: Schematic diagram of the vapor phase sorption-desorption study