Studies of sebum. 8. Observations on the squalene and cholesterol content and the possible functions of squalene in human sebum

Abstract

The squalene and cholesterol contents of the sebum from the backs of normal children and adults were studied. It is confirmed that the squalene content of sebum is lower and the cholesterol content higher in children than in adults. A relationship between the sebaceous activity of a particular area of skin and the squalene and cholesterol content of the sebum derived therefrom is demonstrated. Dilution of the surface-film lipida by lipids from the horny-layer cells significantly alters the composition of the sebum in areas of skin with low sebaceous activity, e.g. most skin areas of the child and the arms and legs of adults. This apparent dilution could account for the observed differences between the squalene content of the sebum of children and that of adults. To avoid this dilution effect, it is suggested that for studies of the composition of sebum the sample should be collected from the back. The wide variations in the squalene content of sebum, both from day to day and between different individuals, is confirmed. This is not due to epidermal contamination of the sample nor solely to variable rates of oxidation of squalene in different samples of sebum. Claims that squalene can inactivate SH groups and inhibit certain enzymes have not been confirmed, and squalene does not appear to possess significant fungicidal or bactericidal properties. It can cause reversible depilation in the rabbit but not in the guinea pig, mouse or rat, and this property is not specific for squalene but is shared by a number of saturated and unsaturated lipids.