EFFICACY OF ANTIDANDRUFF FORMULATIONS 79 ß ß ß ß ß ß e eeee el ß ß ß ee ß ß e e ß ß ß ee ß • e•e ß ß ee e ß ß . Right(Thousands) Figure 3. Duplicate corneocyte counts on opposite sides of subjects with and without dandruff Relationship of Clinical Grade and Corneocyte Count Clinical grades and corneocyte counts ought to be highly correlated pre- sumably, the greater the production of horny cells, the more visible the scal- ing. Procedure Grades and counts were done simultaneously on 141 individuals (some studied twice) giving 296 pairs of observations. The counts were duplicates from opposite sides of the vertex. Approximately half the pairs (150) were from dandruff subiects with grades of 5 and above. It is important to note that corneocyte counts in an unselected population follow a log-normal distribu- tion averages and statistical analysis therefore are .always based on logarith- mically transformed data. Results The orthogonal regression line was calculated from the geometric means (Fig. 4). One can perceive that higher counts tended to be associated with

80 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 1.2 I I I I I i i ! 2 3 4 5 6 7 GRADE Figure 4. Orthogonal regression of corneocyte counts on grades with 95% confidence limits of the calculated line higher grades. This correlation was significant (r = 0.415) but rather weak, barely satisfying tests of significance. Comment While this result was anticipated, the data make it necessary to introduce other considerations. Although a general parallelism was observed, individual disjunctions were quite prominent. Some persons with high counts had sur- prisingly low grades and vice versa. Evidently the eye sees something not measured by the count. We propose the following explanation. Dandruff is the summation of two processes an increased production of horny cells and desquamation in larger flakes. Horny cells are not shed singly but in aggre- gates (15). Although there is considerable overlapping, the proportion of larger scales is much greater in dandruff than in nondandruff. The corneocyte count is most powerful in determining the quantity of horny cells while the eye has special keenness in sensing the size of the scales. The application of irritants such as sodium lauryl sulfate and kerosene to normal scalps affords a good illustration of how the counts may be extremely high and yet there may be no gross sign of dandruff. After about 5 days there occurs a brief flurry of scaling the scalps return to normal by 10 days. Despite the normal appearance the counts were very high, often considera- bly in excess of the worst cases of dandruff (2 x 106/cm2). Clearly the rate of production of horny cells was being greatly accelerated by the process of irritation but this could not be detected by the eye because desquamation was