Effects of permanent waving on changes of protein and physicomorphological properties in human head hair

Two types of permanent waving [digital perm (DP) and croquignole winding perm (CWP)] and two waving lotions [cysteamine-HCl, pH 9.31, liquid type (lotion A) and sodium thioglycolate, pH 9.97, cream type (lotion B)] were used for this study. The protein content was decreased by permanent waving treatments on the whole, and the degree of reduction was dependent on the hair styling and waving lotion used. The greatest decrease (by 58%) was found in hairs processed with the three-treatment performance of DP using lotion B. SDS-PAGE identified the presence of the two most abundant polypeptides, with approximately 48 kDa and 60 kDa, and two large polypeptides, with approximately 200 kDa and 210 kDa, which would belong to the keratin family. Some physical properties of the hairs (tensile strength, diameter, swelling, and elongation) were examined with the permanent waving treatments. In general, the repeated waving treatment and the use of lotion B showed more negative effects on hair care than other treatments. Some morphological changes were observed with a scanning electron microscope (SEM). The most prominent change in the hair surface was observed in the hair specimen with the three-treatment performance of DP using lotion B. More severe signs of damage appeared on the hair with lotion B than with lotion A. As the numbers of permanent waves increased, the degree of damage to the hair surface increased on the whole. However, there was no indication of changes to the hair surface with one permanent waving treatment, as determined by SEM analysis.