What is one common ingredient found in permanent wave solutions?

Ammonium thioglycolate is a primary ingredient in permanent wave solutions because it serves as a reducing agent that breaks the disulfide bonds in hair. This process allows the hair to be reshaped and permanently curled or waved. When applied, ammonium thioglycolate penetrates the hair shaft, facilitating the alteration of its natural structure which enables the hair to form new bonds in the desired shape after being wrapped around rods or curlers.

The other substances mentioned do have roles in hair treatments but do not serve the same function as ammonium thioglycolate in permanent waving. Hydrogen peroxide, for example, is often used as an oxidizing agent in hair lightening and coloring. Alcohol can help to dissolve other ingredients or can be used for cleansing, while sodium chloride is typically associated with adjusting the salinity of solutions but does not have a direct role in creating curls.