Some aspects of hair regreasing.

Synopsis A multi-technique evaluation of the hair regreasing process is described. Preliminary experimentation in vitro was followed by a long-term in vivo study conducted on a single subject having greasy hair. First, a shampoo for very greasy hair and one for dry hair were applied to the left and right sides of the head respectively (split-head test) for 7 weeks; then a shampoo for greasy hair was applied to the entire head (whole-head test) for 5 weeks. Three parameters were studied: (1) hair spacing, determined by means of a special device; (2) regreasing of individual hairs, measured using the contact-reprint technique; (3) the amount of sebum extracted from individual hairs, performed by g.l.c. determination of squalene. Results obtained during the split-head period showed that the shampoo for very greasy hair showed higher average hair spacing, slower progression of regreasing, and better sebum-removal efficiency when compared to the shampoo for dry hair. During the whole-head test period with one shampoo, results showed that there was consistent asymmetry as regards hair spacing and progression of regreasing. These results support our hypothesis concerning the role of interfacial forces in the hair regreasing process.