THE NATURE OF DANDRUFF 119 Figure 1. Dandruff, 5 days after injection of tritiated thyroidinc (630 x) cells with labeled nuclei have already reached top of epidermis Figure 2. Nondandruff, 5 days after injection of tritiated thymidine (630 x) labeled cells are fewer than in dandruff and have migrated only to about mid-epidermis

120 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS until the label is lost at the base of the SC due to dissolution of the nucleus. The method is crude, because labeled cells leave the basal layer at different times, and so certain ones may be near the top, while others have scarcely begun to move. Biopsies were taken from 8 dandruff subjects and 7 without dandruff 4 to O days after injection of tritiated thyroidinc (Figs. 1 and 2). In every in- stance, labeled cells migrated more rapidly through the epidermis in dandruff. In the dandruff subjects, after five days, many labeled cells had reached the granular layer just beneath the SC. After seven days, there were far fewer labeled cells, indicating that many had moved into the horny layer. The viable epidermis in dandruff, therefore, turns over in about a week or so. VI. THE CORNEOCYTE COUNT The foregoing studies indicate a faster generation of epidermal dandruff. This means, of course, that more horny cells are being shed. A use- ful way of demonstrating this is the corneocyte count, a procedure which we originally devised to quantify the cutaneous microflora (7). The sampling technique removes corneocytes in the desquamating loose outer zone. This is accomplished by placing a 3.8 sq cm glass cup on the .clipped scalp. One ml of a buffered nonionic detergent is placed in the cup, and the surface rubbed vigorously with a teflon rod for 1 min. This is repeat- ed once more. The samples are pooled and then mechanically agitated to dis- perse the cells. A few drops of crystal violet are added, and the cells are counted in a Fuchs-Rosenthal hemocytometer. The corneocyte count is always performed 4 days after a bland shampoo and is expressed as the quantity of horny cells per square centimeter per 4 days. On the scalp, horny cell aggregates tend to be retained, shielded by the hairs. The count then is an indirect measurement of cell turnover. In the same individual, the counts are remarkably repeatable time after time, whether or not the subject has dandruff. From what has been said, one would expect a positive correlation between clinical grades and corneocyte counts. When the regression line for 208 pairs of observations was plotted, the grades and counts did indeed parallel each other, but the correlation was wcak, just achieving statistical significance (r equals 0.415) (1). This seemed a bit odd, but the reason soon came to light. A few individuals with Grades IV and V (mild and moderate dandruff) had unexpectedly low counts, while conversely, some Grade II and III scalps had counts which were more characteristic of the dandruff group. These un- usual individuals accounted for the uncomfortably large standard deviations around the mean. As a rule, however, Grade V subjects had counts exceeding 800,000 cells per sq cm while values of less than 500,000 per sq cm were typical of nondandruff subjects (Fig. 3). One cannot decide on the basis of