2 Iconography
Access to the text (HTML) Access to the text (HTML)
PDF Access to the PDF text

Access to the full text of this article requires a subscription.
  • If you are a subscriber, please sign in 'My Account' at the top right of the screen.

  • If you want to subscribe to this journal, see our rates

Journal of the American Academy of Dermatology
Volume 62, n° 3
pages 402-408 (mars 2010)
Doi : 10.1016/j.jaad.2009.04.061
accepted : 14 April 2009
Original Articles

‘Relaxers’ damage hair: Evidence from amino acid analysis

Nonhlanhla P. Khumalo, FCDerm, PhD a, , Janet Stone, BSc, PhD c, Freedom Gumedze, PhD b, Emily McGrath, MRCP d, Mzudumile R. Ngwanya, FCDerm a, David de Berker, MRCP d
a Division of Dermatology, Groote Schuur Hospital, University of Cape Town, Cape Town, South Africa 
b Department of Statistical Sciences, University of Cape Town, Cape Town, South Africa 
c Department of Clinical Biochemistry, Bristol Royal Infirmary, Bristol, United Kingdom 
d Department of Dermatology, Bristol Royal Infirmary, Bristol, United Kingdom 

Reprint requests: Nonhlanhla P. Khumalo, Division of Dermatology, Groote Schuur Hospital, Ward G23, Observatory 7925, University of Cape Town, Cape Town, South Africa.

‘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.

The full text of this article is available in PDF format.

Key words : African hair, amino acids, cystine, hair fragility, hair relaxers, hair straightening

Abbreviations used : TN, TTD

 Funding sources: Dr Khumalo’s post at the time of the study was funded by the Discovery Foundation of South Africa.
 Conflicts of interest: None declared.

© 2009  American Academy of Dermatology, Inc.@@#104156@@
EM-CONSULTE.COM is registrered at the CNIL, déclaration n° 1286925.
As per the Law relating to information storage and personal integrity, you have the right to oppose (art 26 of that law), access (art 34 of that law) and rectify (art 36 of that law) your personal data. You may thus request that your data, should it be inaccurate, incomplete, unclear, outdated, not be used or stored, be corrected, clarified, updated or deleted.
Personal information regarding our website's visitors, including their identity, is confidential.
The owners of this website hereby guarantee to respect the legal confidentiality conditions, applicable in France, and not to disclose this data to third parties.
Article Outline