Final answer:
A perm is a thio-based chemical service that reformats curly and wavy hair into looser and larger curls and waves by disrupting and reforming disulfide bonds. Chemical depilatories also break disulfide bonds in keratin to remove hair from the skin.
Step-by-step explanation:
A perm is a thio-based chemical service that reformats curly and wavy hair into looser and larger curls and waves. The process involves disrupting and reformation of disulfide bonds in the hair strands.
In the permanent wave process, a basic reducing substance, usually ammonium thioglycolate, is used to reduce and rupture the disulfide cross-links in the hair. Once the hair is put on rollers or curlers, an oxidizing agent is applied to reform the disulfide bonds in their new positions, resulting in a permanent change to the hair's structure.
Chemical depilatories, on the other hand, break the disulfide bonds in keratin to remove hair from the skin. The active ingredients, salts of thioglycolic acid and thiolactic acids, react with cystine in the hair to form dithiodiglycolic acid and cysteine, leading to the removal of hair.