Reduction in Hair Waviness by Rubbing Hair Treatments into Hair and Its Mechanism of Action

Abstract

In beauty salons, a hair treatment technique is used in which hair that has had a treatment applied to it is rubbed with the hands in the hope of enhancing the effect of the rinse-off hair treatment. Sensory evaluation of the process of rubbing treatment into hair confirmed a reduction in hair waviness and an improvement in the overall silhouette. To elucidate the mechanism behind this waviness reduction effect, we investigated the dyeing behavior and penetration region of basic red 51, which was incorporated into the treatment as a marker. Furthermore, we examined the structural changes in non-keratin protein aggregates and the accompanying changes in physical properties. The results showed that the treatment rubbing operation 1) increased the volume and area of penetration of basic red 51 dye used as a marker, 2) changed the hair into a uniform and flexible material, 3) reduced the distortion caused by rearrangement of the non-keratin protein aggregate structure during the blow-drying operation while straightening wet hair and made the cohesive structure more uniform. The treatment rubbing operation relaxes the non-keratin protein aggregates in the hair while increasing the penetration area of the treatment ingredients into the hair. Subsequently, during any blow-drying operation while the hair is straightened, the loosened non-keratin protein aggregates tend to rearrange more uniformly along the fiber axis, leading to a reduction in hair waviness.