Seba

It is of interest that horse sebum contains squalene, whereas the seba of ruminants, including sheep, goat, llama and dromedary, contain isocholesterol.

The changes in the composition of the sterols (as well as the effects upon the composition of the aliphatic monohydric alcohols and fatty acids) were greatest in the seba of the two rats which also exhibited lowering of the corrected secretion rate (p. 101); the seba of the other two animals were almost identical with that of the control group.[…]So far only the seba of man and sheep have been studied in detail; only preliminary data are available about the composition of the skin surface lipids of other mammals, including the common laboratory animals.[…]Guinea pig, mouse and rabbit. All these seba are similar in lacking squalene, isocholesterol and triglycerides, exhibiting low values for free fatty acids and containing lathosterol (Wheatley, 1953, 1956; Wheatley & James, 1957).

They investigated the seba of two patients by gas liquid chromatography (this method being sensitive to less than 1 part per 10 million) 12 months after the onset of the lesions and at a time when the disease process was still active.

Although studies on non-human seba are not extensive, we do have evidence that major differences in sebum chemistry occur even between closely related species (Nicolaides et al., 1968, 1970).[…]Although the seba of all species of mammals examined contain esters of some kind, these are generally not triglycerides, but other classes of ester which are less readily hydrolysed by microbial activity. Thus, the seba of rodents, the rabbit and sheep are low in triglyceride and also in free fatty acid, while neither of these compounds classes are observed by TLC in the hair lipids of the chimpanzee, baboon, hamster, guinea pig, cat, dog or cow (Nicolaides et al., 1968).[…]These latter are present in the seba of all species studied, although in some cases such as the mouse, rabbit, goat and cattle, their levels are relatively low.

More than half of human sebum is composed of triglycerides and free fatty acids, whereas the seba of sheep, rabbits and rodents contain less than 10 per cent free fatty acids and almost no triglycerides.