Lye vs. No-Lye Relaxer: What's the Difference?

Woman smiling under an umbrella
 Maskot/Getty Images

When it comes to chemically straightening your hair, there can be a lot of confusion about which products to use, especially when you're bombarded with shelves of boxes and promises of silky, flowing hair at every turn. One thing that can be particularly confounding is the difference between lye and no-lye relaxers. 

The main, active ingredient in a lye-based relaxer is sodium hydroxide. The pH level is higher in a lye relaxer than a no-lye relaxer (approximately 12-14 for lye, 9-11 for no-lye, whereas your hair should typically have a pH of around 4-5).

Does this higher pH make a lye relaxer worse for your hair? In short, kinda. A lye relaxer works to break down the hair's bonds more quickly, which is good because you often experience more scalp irritation with this chemical; the faster it works, the sooner you can rinse it out. They tend to rinse cleanly and quickly with a good neutralizing shampoo follow-up. But still, the fact it breaks down the hair's bonds more quickly means that if you don't actually rinse it out quickly, it could break your hair. Like with all relaxers, you need to be careful.

In turn, the main, active ingredient in a no-lye based relaxer is calcium hydroxide or guanidine hydroxide. Although the pH level of a no-lye relaxer is typically lower than a lye-based one, no-lye relaxers are often associated with dryer hair. This is due to an unintended side effect, which is potential calcium buildup.

One of the major reasons someone might prefer a no-lye relaxer is if their scalp is sensitive, as the chemicals in this type of relaxer can be milder on the scalp.

Regardless, that doesn't mean that it's better to use on children or that the chemicals can't still burn you, because they can.

Unfortunately, like with lye-based relaxers, people sometimes make the mistake of leaving a no-lye relaxer on the hair for too long. This can lead to dry, dull hair due to over-processing.

To remove calcium buildup, try a clarifying shampoo once a month or so to remove dulling deposits. Since clarifying cleansers are often drying, a deep conditioning treatment should be a regular part of your hair care routine about once a week, for any kind of relaxer-treated tresses.

The bottom line is that all relaxers contain chemicals that break down the hair's natural bonds in order to straighten it, and that one relaxer doesn't fit everyone's needs. It's best to consult with a professional to determine what your particular needs are when it comes to relaxers. And no, you cannot apply a lye relaxer over hair that's been processed with a no-lye relaxer or vice versa! However, you can apply a different relaxer to new growth if your current straightener isn't giving you the results you want. Don't constantly be switching relaxer types or brands, though. Once you find the relaxer that works for you, it's best to stick with it until or unless it stops.