Cosmetic and amino acid analysis of the effects of lye and no-lye relaxer treatment on adult black female South African hair.

Surveys indicate that many South African women use relaxers to straighten their hair for cosmetic reasons, which can damage the hair and scalp. The objective of this study was to assess the effects of treating hair with two types of relaxers: Product A (a lye relaxer, sodium hydroxide base) and Product B (a no-lye relaxer, guanidine hydroxide base). Five adult black female South African subjects were used for the study that was divided into two parts. The first part used a half-head study design in a clinical study in which the researcher and the subjects visually assessed various hair quality parameters before and after relaxer treatment. Product B was assessed to perform better (p = 0.032) than Product A in terms of hair straightening. The second part of the study involved hair amino acid analysis by reversed-phase high performance liquid chromatography. There was a decrease in the amount of cystine [Median (range) g/100 g hair] after treatment with both Product A [7.8 (2.5-9.9), p = 0.086] and Product B [4.0 (2.9-4.8), p = 0.005] compared to before treatment [9.1 (6.4-11.9)]; this decrease was greater (p = 0.085) for Product B. Reduction in cystine content was consistent with increased straightness. Product B (the no-lye relaxer) was found to be more effective and safer to use.