Ask Harley


How does a perm work?

A perm, or permanent, is a hair-styling process used to change the shape of hair. Perms work by using chemicals to alter the physical characteristics of hair, and as such, can be used to curl straight hair or to straighten curly hair. (It is a truism of fashion that most women want hair different from what they have naturally.)

Hair is mostly made up of a protein called keratin. Like all proteins, keratin consists of strings of amino acids, building blocks that join together to form complex, three-dimensional structures. One of the amino acids in keratin is called cystine. Among the amino acids, cystine is unique in that it consists of two parts that are held together by a pair of sulfur atoms, a connection referred to as a disulfide bond.

The basic idea behind a perm is to use a chemical, called a reducing agent, to break the disulfide bonds within the outer surface of the hair. The hair is then reshaped by using curlers. Then, another chemical, an oxidizing agent, is used to create new disulfide bonds in order to hold the hair in its new position.

In the process, the hair is inevitably damaged to some degree, but then, beauty does require sacrifice (not to mention time, money and the eye of a beholder).