Alkaline peroxide treatment induces acquired unruly hair by apparently affecting distinct macrofibrils

Individual hairs can be inherently curly; however, bleach treatment can cause damaged hairs to acquire a curl, a phenomenon we term acquired unintentional unruly hair. Because there have been no reports concerning acquired unintentional unruly hair, the influence of bleach treatment with alkaline peroxide that produce this phenomenon was investigated. First, it was validated that the radius of curvature in many curly hairs is reduced upon bleach treatment. Next, the influence of bleach treatment on the mechanical properties of inner components was studied by the force curve method using atomic force microscopy. This measurement revealed four types of macrofibrils-on the orthocortex- or the paracortex-like structure, and on the concave or the convex side-have different mechanical properties. Macrofibrils on the orthocortex-like structure on the convex side were especially influenced by alkaline peroxide treatment, and may be particularly important to acquired unintentional unruly hair.