J, Soc. Cosmet. Cbem. 22 681-699 (1971) ¸ 1971 Society of Cosmetic Chemists of Great Britain Hair lipidsI. fatty materials The from extraction of hair clippings K. V. CURRY* and S. GOLDINGi Presented on loth March 1971 at the Symposium on "Appendages of the Skin", organised by the Society of Cosmetic Chemists of Great Britain in Eastbourne, Sussex. Synopsis--A method for the EXTRACTION of HAIR LIPID in a form as near as possible to that in which it exists on the hair has been established. The effect of TIME of extraction, using DIETHYL ETHER, METHYLENE CHLORIDE and ETHANOL has been studied and the effect of EXTRACTION TEMPERATURE on the amount and nature of material extracted from hair with ethanol has also been investigated. The existence of a layer of fatty acid bound to hair with calcium ions has been postulated. The possible effects of CALCIUM BOUND FATTY ACIDS in the assessment of DETERGENCY efficiency of SHAMPOOS on hair using solvent extraction techniques is also indicated. INTRODUCTION The fatty material found on hair is often loosely called "sebum". In fact, it is a mixture of fresh and aged sebum, epidermal lipid from keratiniz- ing skin surface cells, together with extraneous materials such as hydro- carbons from the atmosphere, detergents and other materials from hair treatment products. In this and subsequent papers the term "hair lipid" will be used to describe the fatty material that is loosely attached to the hair surface and is readily removed by solvent extraction the term "sebum" is reserved for the material secreted by the sebaceous glands. The removal of fatty materials from hair is of prime importance in hair *Unilever Research, Isleworth Laboratory, 455 Lond•)n Road, Isleworth, Middx. iN.V. Vinolia-Gibbs S.A., Rue Bollinckx 352, B-1190 Brussels, Belgium. 681

682 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS treatments, particularly those which involve cleaning of the hair. It is also of importance in treatments such as colouring, bleaching and waving of hair since the presence of a lipid barrier on the hair surface can affect the penetration of active constituents. A knowledge of hair lipid is also im- portant when considering the properties of hair, particularly its condition and whether it is dry or greasy. There is little published information on hair lipids, and even such a simple figure as the quantity of lipid which may be found on hair and its relation to the time since the hair was washed has not been reported in the literature. The probable reason for this dearth of information is that a rapid and convenient method for collecting hair lipid has not been available, and most investigators have concentrated on the study of skin surface lipids using the forehead and arms as the main collecting areas. The difficulties encountered when collecting lipid from hair do not arise when samples are collected from skin, where simple swabbing or absorption techniques can be used references (1, 2) are typical. The area to be sampled is cleansed with solvent and the freshly exuded skin lipid is collected after a suitable time interval. Numerous studies have been carried out using this type of pro- cedure to investigate factors such as the casual lipid level of skin, the lipid replacement time, the mode of secretion of sebum and its composition. The work of Kligman and Shelley (3), and of Wheatley (4) are representative of studies of this type. However, no similar studies on hair lipids have been found in the literature. The aim of this work is to establish a rapid and reliable method of collecting hair lipid, in a state as near as possible to that in which it exists on the hair surface, in order to be able to study the quantity and properties of this matehal. The only method which would allow the lipid to be obtained in an entirely unchanged physical state would be one in which the lipid was scraped from the hair surface. This is obviously impractical and attention has been focused on the use of a solvent extraction method, in which the aim has been to develop a standardized method which would remove the lipid from the hair efficiently but under mild conditions. The use of solvents for cleaning hair (5) and wool (6) has been known for some time and a number of workers have used solvent extraction tech- niques in the laboratory evaluation of shampoo detergency (7-10). How- ever, none of these authors carried out systematic studies of the extraction method, nor did they examine the effect of the extraction procedure on the quantity or quality of the lipid obtained. Indeed they have not