How Does a Perm Curl Your Hair?

A standard perm uses ammonium thioglycolate to break the natural disulfide bonds that create the natural texture of hair while it's in curlers. Then, a neutralizing agent stops the bond-breaking process and allows the hair to form new bonds that lock it into the shape of the curlers.

Hairdressers often use hydrogen peroxide as a neutralizer in a traditional cold perm. When applied, hydrogen peroxide enables the keratin molecules in the hair to form new bonds. This process happens while the perm sets over time.