Hair lipid and surfactants. Extraction of lipid by surfactants and lack of effect of shampooing on rate of re-fatting of hair.
Synopsis The efficiences of extraction of hair lipid by aqueous solutions of surfactants, using a one-stage washing procedure, are highly variable, roughly averaging 50% of the lipid readily extractable with diethyl ether at room temperature. Anionic surfactants are significantly more efficient than the non-ionic surfactant, Tween 20(R). Repeated washing of hair continually removes lipid. It is suggested that a one-stage washing procedure removes essentially all the hair-surface lipids and that differences in cleaning efficiences of surfactants reflect differences in the amounts of internal hair lipid eluted. Variation of the frequency of shampooing from once to three times weekly had no significant effect on the rate of re-fatting of hair when two anionic surfactants in commercial shampoo formulations were investigated, i.e. no evidence was obtained in support of either the hypothesis for a feedback mechanism for control of the level of hair lipid, or the suggestion that surfactants can directly stimulate sebaceous gland activity.
Shaw
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Unilever Research, Isleworth Laboratory, 455 London Road, Isleworth, Middlesex.