title: Protein loss in human hair from combination straightening and coloring treatments.
abstract: BACKGROUND
  Hair chemical treatments, such as dyeing and straightening products, are known to cause damage that can be assessed by protein loss.
  
  
  OBJECTIVE
  The aim of this study was to evaluate the hair protein loss caused by combined chemical treatments (dye and relaxer) using the validated bicinchoninic acid (BCA) method. Three kinds of straighteners, based on ammonium thioglycolate, guanidine hydroxide and sodium hydroxide, were evaluated and the least harmful combination indicated.
  
  
  METHODS
  Caucasian virgin dark brown hair tresses were treated with developed natural brown color oxidative hair dyeing and/or straightening commercial products based on ammonium thioglycolate, sodium hydroxide, or guanidine hydroxide. Protein loss quantification was assessed by the validated BCA method which has several advantages for quantifying protein loss in chemically treated hair.
  
  
  RESULTS
  When both treatments (straightening and dyeing) were combined, a higher negative effect was observed, particularly for dyed hair treated with sodium hydroxide. In this case, a 356% increase in protein loss relative to virgin hair was observed and 208% in relation to only dyed hair. The combination of dying and relaxers based on ammonium thioglycolate or guanidine hydroxide caused a small increase in protein loss, suggesting that these straightening products could be the best alternatives for individuals wishing to combine both treatments.
  
  
  CONCLUSIONS
  These results indicated that when application of both types of products is desired, ammonium thioglycolate or guanidine hydroxide should be chosen for the straightening process.
authors.affiliation: Faculty of Pharmaceutical Sciences of University of São Paulo, São Paulo, SP, Brazil.
authors.forename: Simone Aparecida
authors.initials: SA
authors.lastname: França-Stefoni
authors.affiliation: Faculty of Pharmaceutical Sciences of University of São Paulo, São Paulo, SP, Brazil.
authors.forename: Michelli Ferrera
authors.initials: MF
authors.lastname: Dario
authors.affiliation: Faculty of Pharmaceutical Sciences of University of São Paulo, São Paulo, SP, Brazil.
authors.forename: Tânia Cristina
authors.initials: TC
authors.lastname: Sá-Dias
authors.affiliation: Healthy Skin Foundation and Hair and Skin Research and Treatment Institute, São Paulo, SP, Brazil.
authors.forename: Valcinir
authors.initials: V
authors.lastname: Bedin
authors.affiliation: Healthy Skin Foundation and Hair and Skin Research and Treatment Institute, São Paulo, SP, Brazil.
authors.forename: Adriano José
authors.initials: AJ
authors.lastname: de Almeida
authors.affiliation: Faculty of Pharmaceutical Sciences of University of São Paulo, São Paulo, SP, Brazil.
authors.forename: André Rolim
authors.initials: AR
authors.lastname: Baby
authors.affiliation: Faculty of Pharmaceutical Sciences of University of São Paulo, São Paulo, SP, Brazil.
authors.forename: Maria Valéria R
authors.initials: MV
authors.lastname: Velasco
mesh_terms: D006197:Hair / Q000187:drug effects* / Q000378:metabolism; D006202:Hair Dyes / Q000737:chemistry / Q000494:pharmacology*; D006203:Hair Preparations / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D011506:Proteins / Q000378:metabolism*
chemical_list: D006202:Hair Dyes; D006203:Hair Preparations; D011506:Proteins
keywords: bicinchoninic acid; dyeing; hair; protein loss; straightening