MODEL SYSTEM FOR DANDRUFF INVESTIGATION 189 If the assumption is made that dandruff is indeed a response to an in- fectious process, then the need for a suitable, experimental animal sys- tem to determine the etiological aspects of this process becomes obvious. It is the object of this report to describe the developInent of such a sys- tem and some experimental parameters which govern it. EXPERIMENTAL Animals The anixnals used in this work were mature albino guinea pigs of at least 12 months age. An area approximately 7 X 14 cm was clipped on the dorsal surface of the test animals no longer than 24 hours before the application of the test materials. The shaved area was normally divided into 4 or 6 spaces, delineated with a felt marking pen. A record of the history of applications to each animal was maintained which detailed the type and date of applications and the reactions noted. Normally 3 or 4 replicates of each treatment condition were run on different animals. Test Systems In most cases, the experiniental systems included a lipid mixture de- signed to mimic natural human sebum. The formula for this mixture is shown in Table I. A 0.2-ml single application of this mixture plus the experimental material was placed in a circular area, 25 mm in diameter, within each delineated space on the shaved back of the guinea pig. The progress of each test was followed daily with a final reading of the degree Tablc I Artificial Sebum Formula Oleic acid 15.2 Coconut fatty acids 1.5 Middle cut fatty acids (1Iydrofol acids 580) •L 13.7 Coconut oil 3.0 Lard 27.3 Lanolin 20.3 Cholesterol 1.9 Squalene 4.0 Wheat germ oil 1.0 Petrolatum 8.0 Glycerol 4.1 Ashland Chemical Co., Columbus, Ohio.

190 .JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS g'- •.:.::'i:...x"':. : .... -?•. • "•'• .... •%":%•'. -•. •:.,• •5-• ' .?. -:.•: - , -* -* •:. .-• ._•-• '.":. • '• "- ,:. .-,¾.4?:: ...' .......... -5 .... .:: " ... ., , ..,:.a"'*: .. :. •7..*• '*': . '. ' * .... .,• . -- ....: ......... . ..... .z ....... ./%*. •.•%. ._ . ..... .. •' :•:.... '•..:..." -- .,--- ........•?...... . .... :• '..• , : ."? e . ..... .•. •,. ,½•.•(•.•' .,: .,,•.::.. Figure I. Illustrations of guinea pig sloughing produced by increasing i•lcrcments of P. oi/ale cells added to artificial sebum. Photographs taken 5 days after initial application of the cell plus lipid mixture. Quadrant numbers refer to snbjectivc severity score in each quadrant