Hair Straightening and Relaxing

 

Hair Straightening and Relaxing

Over the last few years permanent hair straightening for women with slight to moderate curl levels has become more popular, mainly driven by products such as Brazilian Keratin treatments (BKT), which use actives such as formaldehyde to cross link keratins in hair to “lock in” the straight style. There have been safety concerns raised about the use of formaldehyde and methylene glycol which have led to new chemistries appearing on the market (e.g. glyoxalin acid). The process for these treatments is to diffuse the cross linking active into hair and then activate cross linking chemistry using heat while setting hair into the desired shape using a flat iron. 

 

In many cases women will refer to hair health benefits deriving from such treatments where these benefits are driven by the macroscopic results straight versus wavy or curly hair. The first is higher alignment of straight versus wavy hair which will improve shine and offer a smoother feel. The second is a frizz improvement where hair remains in its straight shape even at high humidity, in comparison to wavy hair which will return to its wavy / frizz configuration. However, in some cases breakage after repeated treatments has been noticed. This is driven in part by the flat ironing high heat used to achieve the final shape.

Another chemistry used for straightening is thioglycolate to break to break disulfides and hydrogen peroxide to re set in the new straight shape. This chemistry is the same as that used in perming and has the same risks of over processing. The hair health benefits that come from a straight shade are higher in this case than for those choosing to add curls. This due to reduced incidence of knot formation, tangles, increased alignment, shine and decreased frizz.

The above two treatments are suitable for those who have low to moderate levels of curl but not for highly curled or coiled hair such as those of African Descent.

In the latter case, more aggressive chemistry is required to restructure hair, and with this come significantly higher levels of damage. Relaxing treatments designed to do this use very high alkalinity (>pH13) with sodium hydroxide (lye relaxers) or guanidine hydroxide (non-lye relaxers) to more efficiently break disulfide bonds and eventually form lanthionine bridges in the straightened shape. As with perms, there is a danger of over processing with this chemistry, leading to very high breakage, and even if used by skilled stylists there will be some breakage observed. Those who regularly relax their hair need to take great care not to cause excessive breakage by regularly using oil treatments and minimizing wash frequency and heat exposure.

Combination of chemical treatments and physical processes can also drive significantly higher cuticle abrasion and breakage due to a number of factors. The first is removal of the hydrophobic f-layer lipid on the cuticle surface by chemical treatments such as coloring and highlighting leaving a surface that is more hydrophilic. This increase frictional forces and also reduces deposition of conditioning actives such as silicones, which can reduce these frictional forces (i.e. the protection benefit of conditioning products decreases). The second is reduction in tensile strength of hair, making breakage more likely. This is especially the case for treatments that involve a significant amount of bond breakage such as perming and relaxing treatments which rely on breaking cysteine to straighten hair.