J. Soc. Cosmet. Chem. 28 317-328 (1977) ¸ 2977 Society of Cosmetic Chemists of Great l•ritain A physical method for qualitative examination of human sebum PIERRE BORE and NOEL GOETZ Research Laboratories, Socidtd L'OREAL, 1, Avenue de Saint-Germain, 93600 Aulnay-Sous-Bois, France Presented on 7 June 1976 at IXth IFSCC Congress, Boston, U.S.A. Synopsis Total lipids from human scalp have been collected from individuals (both sexes and of different ages), and examined by differential scanning calorimetry. Melting endotherms have been plotted between --100 and + 50øC. The curves tend to change with the age of the subject. The shape of the curve is a physico-chemical property of sebum, from which a diag- nosis, seborrheic or not seborrheic, may be obtained. This new parameter has been correlated with other properties of sebum. Introduction The film of scalp lipids is composed of: sebum resulting from sebaceous gland excretion lipids proceeding from the Malpighi (1) layer epidermal cells and waste fatty fractions. Due to the preponderance of scalp sebaceous glands, these three elements are nor- mally referred to collectively as sebum. This human sebum has been studied, with special regard to: its composition (1) (2) (3) (4) (5) (6) the factors which influence its production (7) (8) (9) (10) (11) the mechanism of its formation (relation squalene-cholesterol). Some authors have been interested in composition variations according to age and sex (12) (13) (14) (15) (16). Our purpose was to define a seborrheic state through consideration of physico- chemical properties corresponding with this state. If one attempts to define seborrheic state from a cosmetic point of view, one can say that it is characterized by: an exacerbation of the fatty and oily aspect of the scalp the presence, on hair, of a more or less thick, shiny, greasy lipidic film which fixes dust and gives an unpleasant heavy aspect to the hair. This subjective evaluation proves to be insufficient to start searches for the anti- seborrheic properties of certain molecules and to measure the evolution of a seborrheic state during a treatment. Our studies on the seborrhea evaluation led us to consider physical and morphological differentiations of sebum. J. L. Burton (17) in 1970, in his study of the acneic phenomenon made some physico-chemical measures of sebum such 317

318 Pierre Bor• and No•l Goetz as: density viscosity surface tension melting point. The extracted amounts of sebum being small, measurements were delicate. In particular viscosity was calculated from the Washburn's equation from capillarity measurement. We have tried to measure the melting endotherms of sebum through the Differential Thermal Analysis technique. The results of this investigation were submitted to cor- relation studies with some physico-chemical parameters and led us to define some pro- perties of sebum corresponding to a non pathogen seborrheic state. Collection methods To obtain sufficiently reliable results it was necessary to obtain appreciable quantities and quantitative samplings of sebum. At present the known methods are: direct suction of the sebaceous gland application to the skin of a sampling rod (7) (8) (9) application of a solvent on the skin surface (18) (19) application to skin of absorbing matter (10) friction of hair followed by washing with solvent (12) (20). The amounts of sebum obtained are determined by gravimetry when the sample is large enough other more or less approximate methods have been proposed when the sample is not large enough e.g. turbidimetry (19), sebograph - sebum-meter (7) (9), colori- metry (21), Acid Number - Iodine Number (19), Oxidation (19). The amounts of sebum obtained thiough point sampling (1 mm 2) have poor reproducibility. These variations prove the heterogeneity of the distribution of sebaceous glands. The composition of the mixture collected depends, to a certain extent, on the method of extraction used (22). In the method now to be described the total amount of sebum present on scalp and hair is collected. The principle is based on the quantitative emulsification of sebum by a sur- factant mixture whose composition has been devised to effect a predetermined deter- gency :-- Sodium laurylsulfate 4.3 g betaine derivative 2.0 g CH3 R -- N -- CH2COO© (R = coprah) I •3 CH3 lactic acid 0.0235 g de-ionized water qs 100 ml The extraction is achieved in two stages: (1) Exactly 15 ml of the surfactant solution are poured on to the wet hair a light massage is used with gloved hands until foam is obtained. It is then rinsed with 1000 ml of de-ionized water and the whole is carefully collected in a measuring vessel. (2) The preceding operation is repeated with 10 ml of the surfactant solution. It is rinsed and collected again in the measuring vessel and the total volume of aqueous sebum suspension is measured exactly. The whole or a part of the •uspension carefully homo- genized is extracted by peroxide free diethyl ether. The ether solution carefully washed with water and dehydrated with sodium sulfate, is evaporated. The sebum is evaluated by gravimetry. The amounts of sebum collected from a given person, at constant time intervals, are reproducible within limits of t 4- 155/o . A detailed analysis of the sebum so