Final answer:
Application of a new Thio relaxer to previously relaxed hair may lead to over-processing, which can cause hair damage including breakage, brittleness, and dryness. Care must be taken to apply new treatments only to untreated new hair growth.
Step-by-step explanation:
Perms and chemical straightening or relaxing treatments alter hair's natural structure through a chemical process. The process involves the application of a reducing agent to disrupt the disulfide bonds within hair strands, allowing them to be reformed into a new shape, whether curly for perms or straight for relaxing. When hair is straightened with a Thio relaxer, it is the disulfide bonds that are broken and reformed to keep the hair in a flattened state.
If a new application of a Thio relaxer is applied to already relaxed hair, there is a risk of over-processing which can lead to hair damage such as breakage, brittleness, and dryness. This is because the hair has already undergone significant structural changes and the additional application can further weaken the disulfide bonds that give hair strength and elasticity.
Therefore, care must be taken to apply new relaxer treatments only to new hair growth where the disulfide bonds have not been previously altered by a relaxer.