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What Are the Differences between a Perm and Relaxer?

By Wanda Marie Thibodeaux
Updated May 21, 2024
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A perm and relaxer are different in that perms usually add curl or wave, while relaxers straighten out the waves or curls already present. They also are separated by the chemicals typically used and application, although the line between relaxer and perm types sometimes blurs. The difference in chemicals makes a perm and relaxer distinct based on pH levels and results, as well.

In terms of mechanical manipulation of the hair, a perm and relaxer are very similar. Both work by lifting up the cuticle or outermost layer of the hair strand and breaking the disulfide bonds deeper within the hair that help provide shape. At this point, the reshaping of the hair depends on the position a cosmetologist puts the hair. For a perm, the cosmetologist wraps the hair around rods or rollers. The cosmetologist puts the hair straight with a relaxer, typically through combing, guiding the hair with the relaxer applicator brush or running the product through the hair with her fingers.

Once a perm solution is on the hair for the recommended amount of time, the cosmetologist must apply a neutralizing solution, which typically contains hydrogen peroxide. The neutralizing solution helps most, but not all, of the broken disulfide bonds reform, causing the hair to reshape based on the structure of the rod or roller. With a relaxer, although a "neutralizing" shampoo is used to restore proper pH to the hair, the neutralizing shampoo does not reform the broken disulfide bonds. This means that a relaxer usually creates weaker hair compared to a perm, although this depends on the exact pH and the condition and type of the hair when starting the chemical process.

Another difference between a perm and a relaxer is chemical makeup. A traditional "cold" perm uses ammonium thioglycolate, sometimes called thio or theo. Some perms that are designed to be gentler use glyceryl monothioglycolate instead; these are called acid or acid-balanced perms, depending on the pH. Traditional relaxers use sodium hydroxide (lye), while no-lye relaxers contain other hydroxides such as calcium hydroxide, lithium hydroxide or potassium hydroxide. Some relaxers use ammonium thioglycolate similar to cold perms, simply omitting the rods and rollers to get a straight effect, so technically, there can be overlap between perm and relaxer products.

Application between a perm and relaxer varies, as well. Perm solutions are liquid in nature, and cosmetologists squirt the product onto the hair from a bottle in most cases. By comparison, a relaxer is usually a paste, which the cosmetologist mixes just prior to starting the application. The cosmetologist brushes the paste into the client's hair.

In terms of pH, relaxers generally are much more alkaline than perms. A regular lye relaxer has a pH between 12 and 14, while a no-lye relaxer has a pH of 9 to 11. The pH of a traditional or alkaline cold perm is 9.0 and 9.6, which is about the same as the pH for a thio relaxer. Acid-balanced perms weigh in with a pH between 7.8 and 8.2, which technically is still basic. Perms in the acid category have a pH of 4.5 and 7.0.

The pH of a perm or relaxer is important for three reasons. First, the higher the pH, the more damage occurs to the hair and the shorter time usually is necessary for the hair to process, forcing the cosmetologist to work very quickly for even results. Secondly, the higher the pH, the greater the chances are of the product irritating or burning the scalp. Lastly, products with lower pH levels are not suitable for resistant or hard-to-process hair and provide gentler, looser results. Those with higher pH levels are not good for previously-processed, dry, very fine or damaged hair and provide tighter results.

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Discussion Comments
By anon962736 — On Jul 25, 2014

No, perms and relaxers are not good for your hair, but it also depends on how you take care of your hair afterwards. Do not get a perm and then in a few weeks to get a relaxer. That's not how it works. You need to get rid of all the hair that is relaxed or permed if you want to add another chemical to it. If you get a perm, and then a relaxer, your hair will fall out and will be severely damaged. I have been getting relaxers for years now and my hair is down to the middle of my back.

By stoneMason — On Nov 01, 2013

Several years ago, I got a perm and it turned out too curly. I waited a few weeks to see if it would loosen and it didn't. So I ended up using a relaxer to loosen it.

It was a huge mistake. My hair got burned and it was extremely fragile. Even if I held my hair, hair strands would snap off. It was a nightmare. I went through many deep conditioners and moisturizing hair masks to make my hair into something I could live with. But even then, it was so damaged. I had to grow out my natural hair and it took a long time to have healthy hair again.

Perms and relaxers are not good for hair. I wish I hadn't had either done.

By bear78 — On Nov 01, 2013

@literally45-- I think that's a terrible idea and I don't think it will work. Like the article said, a perm and a relaxer contain different chemicals. If they had the same composition, stylists would be substituting one for the other all the time but they don't. The only commonality between a perm and a relaxer is that they are both permanent.

If you want to straighten your hair, use a relaxer. If you want to loosen your curls, use a texturizer. And if you want curls, go for a perm. But don't do any of these back to back or your hair will get burned and shed.

By literally45 — On Oct 31, 2013

Can I use a perm solution to relax hair? Instead of putting in rollers after the perm solution, if I keep hair straight, will it relax hair?

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