Damage limitation: comparing the impact of polymers on bleached hair, when applied within or as post-bleach treatments

Hair bleaching causes undesirable chemical and structural changes to the cortex, the most prominent process being the oxidation of the disulphide bonds of the amino acid cystine and the creation of cysteic acid. It is known that this process affects mostly the Keratin Associated Proteins (KAP) which are amorphous and sulphur-rich. A major secondary effect is the overall destabilisation of the cortex structure within which the crystalline Intermediate Filaments’ (IF) proteins are supported by KAP. An overall decrease in the proportion of ordered protein structure, reduction of mechanical strength and the denaturation temperature of hair have been used to quantify the degree of damage. The cuticle also undergoes oxidative damage during bleaching which causes reduced thickness and increased surface roughness.

Mitigating and counteracting these changes in the hair surface and internal structure have been a prime objective of the haircare industry. Such action would be expected to deliver immediate sensory benefits perceivable by the consumer.

This project was to compared the impact of three actives said to deliver structural benefits to bleached hair. Their impact was evaluated in two conditions: when applied with the bleaching cream (WB) and after bleaching (AT).