I. Soc. Cosmet. Chem., 24, 395-398 (May 23, 1973) Laboratory and Clinical Evaluation of Antidandruff Preparations BERNARD IDSON, Ph.D.* Presented December 11, 1972, New York City Synopsis-Accelerated epidermal mitosis, which is characteristic of DANDRUFF, can be studied by incorporation of ISOTOPIC LABELING into cells, counting of the number of CORNEOCYTE CELLS, ULTRAVIOLET fluorescence microscopy, and determination of the levels of SULFHYDRYL in scalp skin. Reduction of the microbial flora of the scalp results in delay of reappearance of dandruff scale. The in vitro antimicrobial inhibition level is still the most widely used preclinical test. Weighing of removed scale is used principally in the LABORATORY. An animal test model using guinea pigs offers promise for it produced a dandruff-like syndrome. Clinical trial techniques are described. INTRODUCTION Dandruff represents an accelerated mitosis, or cell turnover resulting in des- quamation of visible scales. In the process of skin keratinization the normal scalp cells lose their nuclei and cytoplasmic content as they become cornified. Dandruff cells retain their nuclei and cellular fragments in their imperfect keratinization. The accelerated mitosis or reduced transit time of cells through the germinal layer of the epidermis, as well as the cytostatic action of anti- dandruff agents, has been followed by use of intradermal injection of radio- labeled compounds, particularly tritiated thymidine, and counting of the corneocyte cells (1). In the latter histological method, a plot of horny layer cells or corneocyte counts against time of use of a product is probably the best objective measurement of effectiveness. The scalp counts of individuals with•dandruff are two to three times as great as in normal subjects (1, 2). In- complete keratinization can also be detected by ultraviolet fluorescence microscopy and determination of the sulfhydryl levels of scalp skin (3). *Hoffmann-La Roche, Nutley, N.J. 07110. 395

396 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS On a use level, the most desirable properties of an antidandruff preparation are the removal of the scurf and suppression of reo.ccurence of the scale until the next use of the product. This is the basis for use of the wide variety of medicated shampoos, which include antimicrobial agents to suppress the growth of organisms, particularly the yeast, Pityrosporum ovale (4-10). When the microbial flora of the scalp is reduced there is significant time lag before the reappearance of scale (1, 8). However, it appears filat antimicro- bial and antidandruff properties are only causally related and antidandruff agents owe their success to further qualities than only antimicrobial properties (7, 10). Nevertheless, the only widely used preclinical screen is the 'in vitro' antimicrobial inhibition test. ANIMAL AND CLINICAL TRLqLS A major obstacle to definitive investigation of dandruff products has been the lack of a meaningful animal model. Recently, a promising system for the production of a dandruff-like syndrome in guinea pigs has appeared (11). The method depends on inducing a sloughing reaction by use of a buffered suspension of commonly occurring scalp organisms contained in a simulated sebmn mixture. The scaling is possibly due to the liberation of free fatty acids resulting h'om the lipolytie activity of the microbes. Relatively simple methods to weigh the amounts of scurf have been used to follow the progress of treatment (4, 5, 12). Finkelstein and Laden (12) used vigorous brushing of the head over a sheet of poIyvinyl acetate and weighed the loose scurf before and after treatment with a test product. An advantage is that each subject serves as his own control. A hand vacuum cleaner can be used containing a removable tared bag (4, 5). The eoIleetion of 30--40 mg of scurf usualIy indicates visible dandruff 40-60 mg is considered "moderate " 60-70 nag "heavy " and greater than 70 mg is classified as "severe." It is diffl- cult to correlate these with clinical evaluations (13). A major soume of vari- ability appears to be thc degree of pressure applied during vacuuming which can, by itself, act as a source of irritation to the sealp(13). The final verdict of the value of a potential antidandruff product eaIls for a well-diseiplined clinical trial (13, 14-17). Of necessity, elinieaI trials involve subjective assessments of progress with significant observer error and bias. AII studies should be "double blinds," with plaeebos virtually identical to the treatment and the exanfiner unaware of whether the subject is receiving or not receiving treat•nent. To ensure that the identity of the test and eonh'ol material is unknown to both the subject and observer, it is desirable to assign several different code Ietters to the test and eontroI products and to random- ize them. This helps avoid the comparing of notes by subjects (14). A further desirable procedure is to use a "cross-over technique," wherein one panel starts with the control or placebo product and the other panel uses the two products in reverse order. Care should be exerted as to the choice of subjects