The cortex (the inner layer responsible for the strength of the hair) is usually depicted as one unit but actually consists of several fibres (known as fibrils) which are neatly and tightly packed together. See diagram below.

Hair fibre magnified

Relaxers (i.e. chemical hair strengtheners) are grouped into two main groups

  • Lye relaxers (contain high concentration of sodium hydroxide)
  • No-lye relaxers (contain high concentration of guanidine hydroxide)

Both of these relaxers work in the same way. Lye relaxers tend to be harder to handle but are thought to be more effective than no-lye relaxers. The former do have a high pH however, pH is not the reason why hair gets relaxed. In fact, if you reduced the concentration of the relaxer to about 1/10, it would still have a pH of 13 but it would not relax hair.

The two main factors that cause hair to be relaxed are:

  • Swelling of the cortex which happens when the relaxer separates the bonds within the proteins of the fibrils (see the diagram below)
  • A process known as super contraction where the broken bonds essentially realign themselves into a configuration that allows the hair to be straight instead of curly
how hair relaxer works
On application of relaxer, the fibrils of the cortex expand by 40 to 50% or more. This expansion of the fibrils creates pressure on the cuticle, causing it to lift.

The effect of the relaxer is permanent but variable.

Hair is very individual (are you tired of hearing that? lol). Different people will have different degrees of straightness. Yes, straight hair can be relaxed too.

The effect of the relaxer is permanent. Reverting of the relaxer which is often reported is related to the true effect of the relaxer. Often after relaxing, additional heat treatments are needed to produce the final ‘poker’ straight result. This will mask the true effect of the relaxer which can produce a range of results from nearly no discernible difference to the original, to curly hair to super straight hair.

Relaxers damage hair in two main ways

  • The cortex of the hair is significantly weakened due to expansion and bond breaking. The strength of relaxed hair is around 30-50% less than that of untreated hair. This means that if relaxed hair is pulled, it will break with half the force required to break untreated hair.
  • The cuticle is damaged by lifting (which can also break/chip or tear the cuticle). This has two effects. First, an increase in porosity – meaning the hair can take up more water and hence expand even more. Second, the oil layers of the cuticle are disrupted. This is thought to contribute to the weakness of the hair cuticle in relaxed hair.

the effect of relaxer on hair cuticle and natural oils

Mitigating Hair Damage due to hair relaxer

  • Washing off the relaxer thoroughly after application (after 15 minutes and shampooing at least three times; more if necessary)
  • Hair conditioning to help smooth the cuticle
  • Ceramides are the new in thing. Ceramides are a component of the cuticle oil (see the previous diagram). When used as a leave-in product they are thought to help strengthen hair. Replacing the oil on hair with any type of oil instead of ceramides may be just as effective.
  • Minimize tension on hair as relaxed hair is weak. So avoid tight ponytails, weaves, and braids.
  • Relaxed hair should not go through another chemical process such as permanent hair colour immediately after relaxing.

General notes about relaxing

  • Relaxing is potentially dangerous. The chemicals involved and their concentrations are at a level where there is a chance of causing permanent injury. Use with caution.
  • The hair in the scalp is not known to be affected by relaxing. This is the reason why retouching the hair is necessary. Retouching is the process of applying relaxer to new growth. It is commonly done after two or more months. It is not recommended to apply relaxer to already relaxed hair.
  • As a precautionary measure, many people apply oil on areas where they do not wish to relax the hair or do not wish to get burned (like ears, forehead, neck, etc). While this is a good measure, it is no substitute for being extremely cautious. The reason why many oven cleaners contain high concentrations of sodium hydroxide is because it is excellent for dissolving oils and proteins. Therefore, if a relaxer lands on an exposed part of the body (we are made up of proteins and oils), do wipe it up quickly.