ABSTRACT
In certain countries hair waving preparations are regulated as drugs. Permanent hair waving has been based on only two classes of compounds–thioglycolates and bisulfites. And only two members of the former have gained any substantial commercial prevalence. These are thioglycolic acid and its salts and the glyceryl ester of thioglycolic acid. Hair is comprised largely of alpha-keratin protein, the properties of which are largely dependent on the presence of cystine sulfur-sulfur crosslinks. Waving of hair results in chemical, physical, and structural changes in hair. Electron spectroscopy for chemical analysis and Fourier transform infrared spectroscopy are powerful techniques requiring only minimal sample preparation. Fluorescence techniques have been used to demonstrate quantitative differences in damage caused by various treatments, and could provide useful information about damage caused by waving. Manufacturing permanent waves is generally simpler than for other cosmetics or personal care products.
