VISUALIZING AND MEASURING SEBUM SECRETION 373 were virtually no droplets. This was especially noticeable in the vicinity of well-devel- oped papules. This satellite zone of inactivity corresponds to histologic observations showing involution of sebaceous glands surrounding highly inflamed follicles (8). Typi- cally in ache, very large and small droplets are densely interspersed. We also found Sebutape useful for monitoring the decline of sebaceous gland activity in ache conglobata patients receiving 1 mg/kg of cis-retinoic acid daily. Diminished pat- terns were clearly discernable by two weeks these were virtually absent by two months. DISCUSSION Too much, or too little, facial sebaceous secretion has been a major impetus for devel- oping quantitative procedures for estimating sebum output. The Strauss and Pochi gravimetric method or some variant of it, in which sebum is trapped in a lipid ab- sorbing matrix, is the source of most of our knowledge of the physiology of the human sebaceous gland (1, 9-12). However, the gravimetric methods require meticulous attention to details and exacti- tude at every step. With hexane extraction of a protected site, loss of sebum is a worry. Then, too, three hours is a rather long time to keep the face immobile. These proce- dures give no information on the amount of sebum extruded from individual follicles. Previous attempts to visualize follicular droplet patterns utilized osmic acid to blacken the sebum (13). Apart from being an obnoxious substance, osmic acid usually gave blurred patterns owing to lateral spreading of sebum in the cigarette paper or smudging by slight facial movements. The lipometer photometric technique has the virtue of simplicity, but we have found that the method lacks sensitivity at either high or low rates of sebum secretion. Sebutape has several advantages. It is simple and convenient. It can be self-adminis- tered. Because of firm adhesion to the skin surface, facial movements do not affect the patterns. Agreeably, sweating has no effect due to the hydrophobic nature of the film. The tiny droplets from vellus follicles are just as sharply defined as the much larger ones from sebaceous follicles. We wish to emphasize that visualizing droplet patterns has importance which up to now has gone largely unrecognized. New insights can be gleaned. One of our stimu- lating observations is that the output from a given follicle is variable and not constant, unlike hair growth. When Sebutape patterns were obtained at weekly intervals from oily persons, we could show that within a matter of weeks, some precisely identified follicles were producing substantially more or less sebum than originally. Follicles pro- ducing voluminous droplets could virtually shut down. The sebaceous gland is a plastic structure whose size and output apparently changes more or less randomly. Awareness of these fluctuations may help us understand such phenomena as pre-menstrual flares of ache. Greater study is warranted. The availability of extremely sensitive analytical techniques such as gas chromatography and mass spectrometry makes it pos'sible to undertake quantitative and qualitative analyses of individual droplets, simply by "punch biopsies" of Sebutape. We would not find it shocking if the composition of sebum varied from follicle to follicle! Sebutape is readily adaptable to all facial areas: the nose, cheeks, chin, and forehead.

374 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Thus, it is quite easy to obtain a facial "profile" from representative areas. Women often declare that they are oily in certain facial areas and dry in others. We have con- firmed this markedly uneven distribution in some individuals. Also, we have found marked discrepancies between subjective estimates of oiliness in different facial regions and objective measurements of sebum production. Many adult females overestimate oiliness. Sebutape enables at least a semi-quantitative objective assessment which may help to rationalize daily cosmetic practices. The values for sebum production obtained by hexane extraction of Sebutape correlate very well with conventional gravimetric techniques. It is entirely practical to make a high contrast photographic record of the follicular pattern and then send off the tapes to a laboratory for quantitative and qualitative analysis. The response to endocrine and pharmacologic treatments which modify sebaceous secretion can be conveniently moni- tored in this way. Nordstrom eta/, of our laboratory have evaluated this sebum-sensitive device in detail (14). They found that sebum production was constant over a six-week period in ten persons. Also, measurement of the quantity and composition of the surface lipids corre- lated highly with those obtained by the conventional hexane extraction technique. ACKNOWLEDGMENTS We wish to thank Dr. Gary Grove for his expert assistance. This work was supported in part by Grants #AG00788 and #AM27253 from the National Institutes of Health. REFERENCES (1) J. s. Strauss and P. E. Pochi, The quantitative gravimetric determination of sebum production, d. Invest. Derre., 36, 293 (1961). (2) H. Schaffer, The quantitative differentiation of sebum excretion using physical methods. J. Soc. Cosm. Chem., 24, 331 (1973). (3) D. St. Legar, C. Berreby, C. Dubuz, and P. Agache, The lipometer: An easy tool for rapid quantita- tion of skin surface lipids (SSL) in man. Arch. Derre. Res., 265, 79 (1979). (4) W. J. Cunliffe, J. N. Kearney, and N. B. Simpson, A modified photometric technique for mea- suring sebum excretion rate, d. Invest. Derm., 75, 394 (1980). (5) US PATENT #4,532,937. (6) G. L. Grove, Dermatological applications of the Magiscan image analysing computer, Bioengineering and the Skin, 3, 173 (1984). (7) M. R. Ruggieri, K. J. McGinley, J. J. Leyden, and J. C. Touchstone, "Reproducibility and Preci- sion of Quantitation of Skin Surface Lipids by TLC," in Advances in Thin Layer Chromatography, J. C. Touchstone, Ed. (John Wiley & Sons, Inc., New York, 1982), pp 249-259. (8) G. Piewig and A. M. Kligman, Acne: Morphogenesis and Treatment (Springer-Verlag, Berlin, Heidel- berg, 1975). W. J. Cunliffe and S. Shuster, The rate of sebum excretion in man, Brit. d. Derre., 81, 697 (1969). R. Brun, K. Endedin, and E. Kull, A propos de Sebum-tests, Dermatologica, 106, 165 (1953). J. G. Smith, The aged human sebaceous gland, AMA. Arch. Derre., 80, 663 (1959). K. K. Jones, M. C. Spencer, and S. A. Sanchez, The estimation of the rate of secretion of sebum in man, d. Invest. Derre., 17, 213 (1951). A.M. Kligman and W. B. Shelley, An investigation of the biology of the human sebaceous gland,.]. Invest. Derre., 30, 99 (1958). K. M. Nordstrom, H. G. Schmus, K.J. McGinley, and J. J. Leyden, Measurement of sebum output using a lipid absorbent tape, d. Invest. Derm., 87, 260 (1986). (9) (10) (11) (12) (13) (14)