J. Soc. Cosmet. Chem., 27, 111-139 (March 1976) The Nature of Dandruff ALS•,RT M. KLICMaN, M.D., Ph.D., K•,NNm• J. McGiN•.•,¾, and JAMES J. Lmq)EN, M.D.* Presented, December 1974, SCC Annual Meeting, New York, N.Y. Synopsis: DANDRUFF is a fine example of the inverse square rule in experimental medi- cine: interest in a problem is inversely proportional to the square of its prevalence. Rare disorders evoke great interest great minds and monies are applied to their study. Con- versely, familiar things are scorned and neglected. Dandruff also illustrates an adverse effect of therapeutic advances: curiosity collapses when a means of control is developed. The power to subdue a disorder weakens interest in its inner qualities. Two paths of investigation, which have long occupied our attention, namely, CUTA- NEOUS MICROBIOLOGY and the HORNY LAYER, finally led us to the SCALP. We have been serious students of dandruff for almost a decade. It is our intent in this paper to tell what we have learned and to present an overview of dandruff in the light of our personal experience. We shall be less concerned here with raw data than with ideas of what dandruff is and how it behaves. I. DEFINITION Dandruff is excessive clinically noninflammatory scaling of the scalp. In the great majority of cases, diagnosis can be made almost instantly by simply inspecting and scratching the surface. Lesions elsewhere on the body call at- tention to disorders which also happen to involve the scalp, notably seborrheic dermatitis and psoriasis. Difilculties arise when the latter are chiefly confined to the scalp for inflammatory changes are masked in this location. Scalp skin is thick and redness and exudation may be hidden by layers of scale. Scaling itself is a very nonspecific sign. Great experience is needed to recog- nize the special morphologic qualities of different dermatoses, viz., the silvery scale of psoriasis or the greasy scale of seborrheic dermatitis. We always in- quire about past and present skin disease. Wrong diagnoses, while not common, are frequent enough to cause some mischief. It is disquieting how often we have mistaken another process for dandruff, most often seborrheic dermatitis in older subjects. Diagnostic er- *Department of Dermatology, School of Medicine, University of Pennsylvania, Phila- delphia, Pennsylvania 19104. 111

119. JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS rors have serious consequences when one is appraising efficacy in a small panel of "dandruff" subjects. Quite recently, another disease, atopic dermatitis, has impressed us by its ability to mimic dandruff. We became aware of this source of error when puzzling over why "dandruff" patients failed to respond to highly effective antidandruff preparations. It turned out that these subjects had atopic derma- titis, often with a background of infantile eczema in association with a family and personal history of respiratory allergies. Since atopics are notoriously unable to tolerate anionic soaps and surfactants, failure to respond to anti- dandruff shampoos should immediately arouse the suspicion that the subject does not have dandruff. When we find that all but 1 of 10 subjects improve, we immediately review the case. Our belief is that dandruff is never com- pletely resistant to such potent drugs as selenium sulfide (SeS) and zinc pyridinethione (ZPT). II. PRUVALU•CE For the most part, statements concerning the proportion of pcrsons who have dandruff are merely "guesstimates." Systematic epidemiologic surveys are expensive and laborious dandruff is, after all, not a health-threatening disorder. To be meaningful, a large unselected rigorously defined population would have to be examined. The frequency with which physicians encounter dandruff patients in their clinics or practices is no measure of prevalence. Neither is the size of the market for antidandruff products. It is easy enough to describe dandruff as excessive scaling. Tension arises over the qualifying adjective: How much is excessive? Lacking objective measurements, we are driven to subjective estimates. The amount of scaling that will be regarded as bothersome will largely depend on social status, the rule being that concern increases directly with height up the ladder. What the ghetto resident would not notice might be a severe embarrassment to a bank president. A few flakes would mar the dignity of a funeral director while a blizzard of scales would likely be ignored by construction workers. The rich are more reactive than the poor to factors influencing self-image, the beautiful more than the plain, the sexy more than the neutral, etc. We appraise dandruff by recourse to the ancient and honorable institu- tion of the professional expert, best exemplified by the wine tasters. The pow- ers of these artists exceed that of gas chromatography when it comes to idcntifying the type, year, and province where the wine was produced. There are virtually no disagreements among the gentleman of this admirable craft. With dandruff, too, an individual with inborn sensitivity and meticulous habits can develop a high degree of reliability. Expert status is not conferred upon the novitiate until he has assessed many hundreds of scalps, preferably thousands. Competency can be objectively validated. The candidate grades