Effects of semi-permanent hair dyes and conditioning polymers on the colour enhancing properties of shampoo formulations

This work investigates the colour retaining efficacy of shampoo compositions, containing polymers and semi-permanent hair dyes, on hair tresses pre-coloured with permanent red oxidative dye. The conclusion was that the addition of polymeric conditioning actives to shampoos contributed to the colour retention of permanently dyed hair, whist the further addition of a cationic dye, at pH above the isoelectric point of hair, produced a weak direct-dyeing effect. Taking into account the short contact time between the semi-permanent dyes and the hair, it is proposed that this effect was due to the colourant deposition on the hair surface. Furthermore, the observed enhanced colour vibrancy and evenness, achieved with the combined polymer/dye treatments, points out to a favourable interaction between those molecules, allowing for more a consistent coverage of the hair surface.