Division of Dermatology, Groote Schuur Hospital, University of Cape Town, Cape Town, South Africa.
J Am Acad Dermatol. 2010 Mar;62(3):402-8. doi: 10.1016/j.jaad.2009.04.061.
'Relaxers' are used by more than two thirds of African females to straighten hair, with easy grooming and increased length often cited as reasons. A recent study reported relaxed hair lengths much shorter than expected, suggesting increased fragility; the potential for scalp inflammation and scarring alopecia remains unclear.
To investigate the biochemical effects of 'relaxers' on hair.
With informed consent, included participants represented 3 groups: natural hair, asymptomatic relaxed hair, and symptomatic (brittle) relaxed hair. Biochemical analysis was performed by using a Biochrom 30 amino acid analyzer. Differences in amino acid levels were assessed using either Wilcoxon rank sum test or matched-pairs signed-rank test.
There was a decrease in cystine, citrulline, and arginine; however, an increase in glutamine was found in all relaxed compared to natural hair. Cystine levels (milligram per gram amino acid nitrogen) were similar in natural proximal and distal hair: 14 mg/g (range, 4-15 mg/g) versus 14 mg/g (range, 12-15 mg/g); P = .139. In asymptomatic relaxed hair, cystine levels were higher in less frequently relaxed samples proximal to scalp: 7.5 mg/g (5.6-12) versus 3.3 mg/g (1.3-9.2); P = .005. Cystine levels in distal asymptomatic relaxed and symptomatic relaxed hair were similar to each other and to those in the genetic hair fragility disease trichothiodystrophy.
It was not possible to analyze lye and no-lye 'relaxers' separately.
'Relaxers' are associated with reduced cystine consistent with fragile damaged hair. A decrease in citrulline and glutamine has been associated with inflammation; prospective studies are needed to investigate whether or how 'relaxers' induce inflammation.
超过三分之二的非洲女性使用“拉直剂”来拉直头发，她们通常会提到易于打理和增加长度这两个原因。最近的一项研究报告称，使用拉直剂后的头发长度比预期的要短得多，这表明头发变得更加脆弱；至于头皮炎症和瘢痕性脱发的潜在风险尚不清楚。
研究“拉直剂”对头发的生化影响。
在获得知情同意后，纳入的参与者代表了 3 组人群：自然头发组、无症状拉直头发组和有症状（易碎）拉直头发组。使用 Biochrom 30 种氨基酸分析仪进行生化分析。使用 Wilcoxon 秩和检验或配对符号秩检验评估氨基酸水平的差异。
与自然头发相比，所有拉直头发的胱氨酸、瓜氨酸和精氨酸水平均降低，而谷氨酰胺水平升高。自然近端和远端头发的胱氨酸水平（每克氨基酸氮中的毫克数）相似：14mg/g（范围，4-15mg/g）与 14mg/g（范围，12-15mg/g）；P=.139。在无症状拉直头发中，头皮近端较少频繁使用拉直剂的样本中胱氨酸水平更高：7.5mg/g（5.6-12）与 3.3mg/g（1.3-9.2）；P=.005。无症状拉直头发和有症状拉直头发的远端胱氨酸水平与各自的水平相似，也与遗传性头发脆弱疾病——先天性硫营养不良症的水平相似。
无法分别分析含碱和不含碱的“拉直剂”。
“拉直剂”与胱氨酸减少有关，这与脆弱受损的头发一致。瓜氨酸和谷氨酰胺的减少与炎症有关；需要进行前瞻性研究，以调查“拉直剂”是否以及如何引起炎症。
