180 JOURNAL OF COSMETIC SCIENCE Figure 3: Silicone deposition on European Brown Hair Figure 4: Summary of Silicone Deposition {Large Silicone Particle Size) from Surfactant B Silicone Particle Size vs Pol mer MW 400 350 � 300 � 250 E i 200 g' 150 en 100 50 Large Particle Size Small Particle Size A-II A-Ill A-PJ A-VI Cationic HEC Molecular Weight The above data suggests that the silicone deposition from silicone containing shampoos onto the hair is a very complex process. Many factors, such as silicone droplet size, cationic polymers, surfactant system and hair type can change the deposition process. The general trend of silicone deposition with different silicone particle sizes and different cationic HEC polymer molecular weight is summarized in Figure 4. In general, more large particle size silicone is deposited by low molecular weight HEC, while more small particle size silicone is deposited by high molecular weight HEC. One of the major roles of cationic HEC in a conditioning shampoo is to control the silicone deposition in order to maintain good overall conditioning performance. Thus, fonnulators need to select the right combination of silicone particle size with the structure of cationic HEC in order to deliver the desired amount of silicone onto the hair. Conclusion: This study demonstrates the importance matching the optimum silicone particle size and cationic polymers structure in order to deliver the desired amount of silicone onto a specific type of hair in a predictable way to maximize the conditioning shampoo perfonnance without causing a silicone buildup issue. References: (/) (2) (3) (4) (5) (6) (7) M.D. Berthiaume, "Silicones in Cosmetics," in Principles of Polymers Science and Technology in Cosmetics and Personal Care, E.D, Goddard and J.V. Gruber, Eds (MarcelDekker, New York, 1999), pp. 275-324. J. Jachowicz and M.D. Berthiaume, "Heterocoagulation of Silicone Emulsions on Kerstin Fibers", Journal of Colloid and Interface Science, Vol. 133, No. I, Nov. 1989, pp. 118-134. M.D. Berthiaume and J. Jachowicz, "The Effect of Emulsifiers and Oil Viscosity on Deposition of Nonionic Silicone Oils from Oil-in-Water Emulsions into Kerstin Fibers", Journal of Colloid and Interface Science, Vol. 141, No.2, Feb. 1991, pp. 299-315. E.D. Goddard, "Measuring and Interpretation Polycation Adsorption," in Principles of Polymers Science and Technology in Cosmetics and Personal Care, E.D, Goddard and J.Y. Gruber, Eds (MarcelDekker, New York, 1999), pp. 465-508. J.V. Grubber, B.R. Lamoureux, N. Joshi, and L. Moral, "The use of X-ray Fluorescent Spectroscopy to Study the Influences of Cationic Polymers on Silicone Oil Deposition from Shampoo", J. Cosmet. Sci., 52, pp. 131-136. R.Y. Lockhead, Conditioning Shampoo, Soap/Cosmetics/Chemical Specialties, PP 42-49, October /992 M. Gamez-Garcia, Polycation Substantivity to Hair, IFSCC, Vol. 4, PP 99-107 (200/)

2005 ANNUAL SCIENTIFIC MEETING 181 MALASSEZIA AND SEBORRHEIC DERMATITIS: ETIOLOGY AND TREATMENT Thomas L. Dawson, Jr., Ph.D. Beauty Care Technology Division, The Procter & Gamble Company, Cincinnati, Ohio, USA Etiologic Mechanism or Dandruff and Seborrheic Dermatitis (D/SD) Dandruff and seborrheic dermatitis are chronic clinical scalp conditions affecting greater than 50% of the population, the primary symptom or which is visibly excessive scalp scaling. Seborrheic dermatitis is a more severe disorder which includes increased desquamation or areas other than the scalp and visible inflammation1• D/SD are more than just superficial disorders of the stratum comeum, including alteration of the epidermis with hyperproliferation, excess intercel\ular and intracellular lipids, interdigitation of the corneal envelope, and parakeratosis1·1. Combination of several recent lines of investigation points out a novel mechanism for the etiology of DISD. Scalp Malassezia degrade sebum, freeing multiple fatty acids from triglycerides. They consume the specific satw"ated fatty acids necessary for their proliferation, leaving behind the unsaturated fatty acids. The free fatty acids then penetrate the scalp skin, and in susceptible individuals breach the skins barrier function and induce a hyperproliferative response4• The role or Sebum Hwnan sebaceous glands (SG) are found over the entire skin surface (except the palms of the hands and soles of the feet), but seburn secretion is highest on the scalp, face, chest, and back5• Seburn is produced under hormonal control, with SG active at birth under the control of maternal androgens. They quickly reduce in size and sebum Mnlnssezia Mediated Degradation of Human Sebum -!lfl&llill..._...__. i.. ................ ,.J.-.,...,J..�11,o-.1��-� , J J 4 111 • • •1111nu1111u•1ta11a production until puberty. As puberty begins the SG activate, this time under the control of circulating androgens. The sebum secretion rate increases throughout the teens, remains steady through the twenties and thirties, then lessens with age1·6. D/SD show a strong temporal correlation with SG activity, following the pattern of early cradle cap, low incidence until puberty, increasing incidence through the teens, 2nd and 3rd decades, then declining1·0. Human sebum is a complex mixture of triglycerides. fatty acids, wax esters, sterol esters, cholesterol, cholesterol esters, and squalene. As the sebum is secreted, it consists primarily of triglycerides and esters, which are broken down by commensal microbes into diglycerides, monoglycerides, and free fatty acids. Human sebum contains both saturated and unsaturated fatty acids, with a preponderance of unsaturates. The fatty acid chain lengths of human sebum vary considerably, but are predominantly 16 and 18 carbons. The role of specific fatty acids of human sebum becomes apparent when we examine the metabolism of Malassezia. Role or Malassezia Over one hundred years ago, Malassez implicated the yeast Malassezia in the etiology of dandruff". While Malassezia are not numerically correlated to dandruff and seborrheic dermatitis (D/SD), recent evidence strongly supports their causal role4• This evidence includes the effectiveness of multiple chemical entities whose sole common mechanism or action is antifungal activity, as well as the very distinct numerical correlation of reduction in severity with reduction of Malassezia numbers9, and there is now general a,reement1 as to their causal role00. Interestingly, Malassezia have a very specific taste for individual fatty acids 1. :_ The Malassezia lipases are non-specific and degrade any available triglycerides (Fig. 2). The saturated fatty acids are consumed, and the abundant unsaturates, predominantly oleic (Cl8:1�9) and palmitoleic (Cl6:1�9) are left on the skin (Fig. 2, Fig.3). Recently, novel molecular methods have overcome the difficulties presented by culture or Malassezia, and the specific Malassezia species present on human scalp have been elucidated4.I , and the most common species on human scalp are M. restricta and M. g/obosa. The Role of Individual Susceptibility It has now been shown that a representative Malassezia fatty acid metabolite ( oleic acid) is able to induce scalp flaking in susceptible individuals, but not in non-susceptible individuals (Fig.2)u. The Malassezia most commonly found on human scalp, M. globosa and M. restricta, non-specifically degrade human seburn and release unsaturated fatty acids like oleic and palmitoleic onto the scalp (Fig. 1). This strongly supports that dandruff sufferers display an underlying defect in permeability barrier function that renders them more susceptible to fatty acid-induced barrier disruption. In this regard, dandruff-susceptibility may be determined, at least in part, by a defect in Role or lndlvldual Sensitivity i.o I 0.5: Flakln1 o.o 1 olelc ,. - + - +