SEBUM FLOW DYNAMICS 119 V-SER (%) 50 40 20 - ß OVER 5 WEEKS 1 0 t t ß LASWE2 - 10 ! •r Shampoo -20 A C D H N P S Z Figure 1. Photometric quantification of the median variation with 95% confidence interval in sebum excretion rate (V-SER) over the five-week use and last-two-week use of antidandruff shampoos (see Table I). Significant changes (*p 0.05) take place versus baseline values. At completion of the study, shampoos S and C significantly increased seborrhea com- pared to all other products and shampoo N alone, respectively. DISCUSSION The pivotal role of M. ovalis in the development of dandruff is generally acknowledged (1-3,8). For cosmetic reasons and pathogenic consideration, it is desirable that the sebum flow dynamics does not increase in response to the use of antidandruff shampoos. Various methods have been used for measurement of the rate at which the sebum flows onto the skin surface. The optoelectronic method we used was specially designed for evaluations made on the scalp (6,7), affording direct reading of the collected amount of lipids (9). The sebum collected over a three- to four-hour period is directly related to the pool of sebum stored in the follicular reservoir (10-12) following its synthesis and secretion by the sebaceous glands. Many studies have shown that the early sebum flow after the skin is cleaned comes mainly from a reservoir in the pilosebaceous follicle, and

120 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS not from any feedback stimulation of the sebaceous gland (13-15). Hence, the present data, which are measures of sebum excretion, give insight into the activity of shampoos on the follicular reservoir function. In addition, since the size of the sebum pool lying within the pilosebaceous duct and the stratum corneum is in part related to the rate of sebum production, the method also provides an indirect measure of sebaceous gland activity. In the present study, most of the antidandruff shampoos showed an absence of significant SER change over time. The discrete trend in SER increase might be related to the removal of dandruff, which allowed the sebum to spread freely at the skin surface. Such a finding confirms the unreality of the so-called reactive seborrhea, in which the seba- ceous excretion increases with the frequency of most hair washes. However, this rule may have exceptions, illustrated by the fact that two shampoos of the present study induced a significant increase in SER. Such abundant sebum flow was already reported following the use of the selenium sulfide shampoo (4,5). Another study using the squamometry and corneosurfametry bioassays had shown that those shampoos promoting seborrhea were those yielding some irritancy potential on the stratum corneum (16). The direct relationship between alterations in sebum flow dynamics and subclinical irritation is suggested, although not proven, by these studies. Only a few topical products are known to decrease the sebum output at the skin surface. Among them, the effect of progesterone (17), astringents (18), erythromycin-zinc com- plex (19), corticosteroids (20), and elubiol (21) have been documented. The 2%- ketoconazole shampoo formulation could be added to that list. It should be compared to the shampoos claiming a presumptive antiseborrheic activity. REFERENCES (1) S. Shuster, The aetiology of dandruff and the mode of action of therapeutic agents, Br. J. Dermatol., 111,235-242 (1984). (2) I.M. Bergbrant, S. Johansson, D. Robbins, A. Scheynius, J. Faergemann, and T. Soderstom, An immunological study in patients with seborrheic dermatitis, Clin. Exp. Dermatol., 16, 331-338 (1991). (3) C. Pidrard-Franchimont, J. E. Arrese, and G.E. Pidrard, Immunohistochemical aspects of the link between Malassezia ovalis and seborrheic dermatitis, J. Eur. Acad. Dermatol. Venereol., 4, 14-19 (1995). (4) H. Goldschmidt and A.M. Kligman, Increased sebum secretion following selenium sulfide shampoos, Acta Dermatol. Venereol., 48, 488-491 (1968). (5) G. E. Pi6rard, C. Pi6rard-Franchimont, and T. Ben Mosbah, Les pityrosporoses. Pityriasis versicolor, folliculite pityrosporique, dermatite s6borrh6ique et 6tat pelliculaire, Rev. Med. LiPge, 44, 267-271 (1989). (6) D. Saint-Ldger and J. L. L6v&que, A comparative study of refatting kinetics on the scalp and forehead, Br, J. Demzatol., 106, 669-675 (1982). (7) C. Pi6rard-Franchimont and G. E. Pi6rard, Approche physiopathologique de la s6borrh6e du cuir chevelu, Ann. Dermatol. Venereol., 115,451-453 (1988). (8) J. E. Arrese, C. Pi6rard-Franchimont, P. De Doncker, A. Heremarts, G. Cauwenbergh, and G. E. Pidrard, Effect of ketoconazole-medicated shampoos on squamometry and Malassezia ovalis load in pityriasis capiris, Cutis, 58, 235-237 (1996). (9) D. Saint L6ger, C. Berrebi, C. Duboz, and P. Agache, The Lipometre: An easy tool for rapid quan- titation of skin surface lipids (SSL) in man. Arch. Dermatol. Res., 265, 79-84 (1979). (10) W.J. Cunliffe and S. Shuster, The rate of sebum excretion in man, Br. J. Dermatol., 81,697 (1969). (11) D.T. Downing, A.M. Stranieri, and J. S. Strauss, The effect of accumulated lipids on measurements of sebum secretion in human skin, J. Invest. Dermatol., 79, 226-228 (1982).