Hair is constantly exposed to a variety of stress factors. There is physical stress, such as blow drying, as well as environmental stress factors like ROS, UV and pollution. In addition, there is chemical stress, which includes coloring and straightening. All of these different factors induce structural damage to the F-layer, the outermost protective layer of the hair, as well as to the hair fiber, according to Mibelle Biochemistry. As a result, the hair becomes more porous, brittle, dull lookin...