How Does Hair Dye Work?

Hair dyes must tear into the hair follicle to deposit colorants that will change the hue of the mane. Dyes can be damaging to hair, especially those dyes that include some bleach. Understanding how hair dyes work can help people decide if they actually want to go through with the process.

Type

Hair dye is either temporary or permanent. The temporary types vary in how they work. Some send pigment molecules inside the hair shaft. Others form complexes inside the strand.

Permanent

More permanent dyes open the outer layer of the hair shaft so that the dye can react with the inner part of the hair. The dye must first remove the original color of the hair and then add a new color to the strand. Chemicals in the dye -- such as ammonia -- cause the cuticle to open, allowing the dye to reach the hair cortex. The peroxide in the dye removes the preexisting color. After applying the dye, conditioners close the cuticle to seal and protect the new color.

Lighten

To make hair lighter, some people use bleach, which does not technically color hair, but is instead a hair color remover, simply penetrating into the hair shaft and dispersing the colorants inside.

Those with black hair can have an especially difficult time changing their hair from black to a more natural color. The black color in the hair must first be stripped out before the new dye can be added using a color stripper kit. These kits can also damage the hair; so waiting for the hair to grow out is often the best option.