Which chemical is commonly used in perms to break disulfide bonds in hair?

Ammonium thioglycolate is the chemical commonly used in perms to break disulfide bonds in hair. This compound works by reducing the cystine bonds in the hair’s structure, allowing the hair to be reshaped into a new form. When applied during the perming process, it penetrates the hair shaft, breaks down the existing disulfide bonds, and enables the hair to take on a new curl pattern when wrapped around perm rods. This property of ammonium thioglycolate makes it particularly effective for creating various types of curls and waves in hair.

In contrast, sodium hydroxide is typically used in a different type of chemical treatment known as a lye relaxer, which is intended to straighten hair rather than curl it. Glyceryl monothioglycolate, while also a reducing agent, is considered a milder alternative to ammonium thioglycolate and may be found in some formulations for softer waves, but it is not as commonly used in standard perm solutions. Hydrogen peroxide is an oxidizing agent primarily used in hair bleaching and lightening processes rather than in the curling or permanent wave process.