With repeated coloring, the color begins to accumulate in the hair shafts leading to swollen areas known as nodes. As more and more nodes are formed the hair becomes dry, rough and develops a tendency to break. These damages are cumulative so that every coloring adds on to the damage caused the by the earlier one which is also referred in American Academy of Dermatology Association. Eventually the nodes begin to break leading to micro fractures along the hair shaft.
Perming is a process of changing the nature of the hair shaft. It involves breaking down the disulphide bonds of the hair and then rejoining them in a shape as desired. The risk is that if disulphide bonds are not rejoined correctly, then the very basic molecular structure of hair breaks down, leading to hair loss and thinning on the scalp.
Hair Straightening is a process of changing curly hair into straight hair. It is the opposite of perming. The process however is the same and involves breaking down of the disulphide bonds to change the basic hair structure to a more desirable pattern.
On a Tricho Analysis, even a single session of hair perming or straightening will show signs of fraying and damage. With multiple sessions marked increase in fraying and damage to the cuticles is seen.