Techniques for Hair Straightening
Traditional thermal straightening uses a hot comb or flat iron[1,2,4,12] to temporarily disrupt hydrogen bonds within the hair shafts, which is reversible with exposure to moisture.[1,2,4,5] Patients repeat this process every 1 or 2 weeks to offset the effects of normal perspiration and environmental humidity.[5,12] Thermal straightening techniques can lead to increased fragility of the hair shaft and loss of tensile strength.
Alternate methods of hair straightening use lye (sodium hydroxide) or nonlye (lithium and guanidine hydroxide) "relaxers" to permanently disrupt hydrogen and disulfide bonds in the hair shaft, which can damage and weaken hair.[1–5,11,12] Touch-ups to the roots often are performed every 6 to 8 weeks.[1,2]
Chemical relaxers historically have been associated with CCCA but have not been definitively implicated as causative.[2–4,13] Most studies have not demonstrated a statistically significant association between chemical relaxers and CCCA because, with a few exceptions, studies have either been based on surveys or have not employed trichoscopy or scalp biopsy. In one of those studies, patients with CCCA were determined to be 12.37 times more likely to have used a chemical relaxer in the past (P<.001). In another study of 39 women in Nigeria, those who had frequent and prolonged use of a chemical relaxer developed scarring alopecia more often than those who did not use a chemical relaxer (P<.0001). However, it is now known that the pathogenesis of CCCA may be related to an upregulation in genes implicated in fibroproliferative disorders (FPDs), a group of conditions characterized by aberrant wound healing, low-grade inflammation and irritation, and excessive fibrosis. They include systemic sclerosis, keloids, atherosclerosis, and uterine fibroids. The risk for certain FPDs is increased in individuals of African descent, and this increased risk is thought to be secondary to the protective effect that profibrotic alleles offer against helminths found in sub-Saharan Africa. A study of 5 patients with biopsy-proven CCCA found that there was increased expression of platelet-derived growth factor gene, PDGF; collagen I gene, COL I; collagen III gene, COL III; matrix metallopeptidase 1 gene, MMP1; matrix metallopeptidase 2 gene, MMP2; matrix metallopeptidase 7 gene, MMP7; and matrix metallopeptidase 9 gene, MMP9, in an affected scalp compared with an unaffected scalp. Still, chemical relaxers weaken the hair shaft and follicle structure, increasing the possibility of hair breakage and allowing for inflammation and trauma to render negative follicular effects.[3,13]
The following interventions can be recommended to patients who thermally or chemically treat their hair to prevent hair damage:
Decrease the frequency of thermal straightening.
Use lower heat settings on flat irons and blow-dryers.
Thermally straighten only clean dry hair.
Regularly trim split ends.
Use moisturizing shampoos and conditioners.
Have a trained professional apply a chemical relaxer, if affordable.
Consider decreasing (1) the frequency of chemical relaxer touch-up (to every 8 to 10 weeks) and (2) the overall manipulation of hair. There is a fine balance between not treating often enough and treating too often: The transition point between chemically processed hair and grown-out roots is a high-tension breakage point.
Cutis. 2022;109(2):98-100. © 2022 Cutis