Effects of Permanent Waving on Changes of Protein and Physicomorphological Properties in Human Head Hair

The study investigated the effects of two types of permanent waving (digital perm and croquignole winding perm) and two waving lotions (cysteamine-HCl and sodium thioglycolate) on human hair. It was found that permanent waving treatments generally decreased the protein content in hair, with the most significant reduction (58%) occurring in hair treated three times with digital perm using sodium thioglycolate lotion. The study identified keratin polypeptides and examined physical properties such as tensile strength and diameter, noting that repeated treatments and the use of sodium thioglycolate lotion had more detrimental effects. Scanning electron microscopy revealed that multiple treatments increased hair surface damage, although a single treatment did not show noticeable changes.