Hair Structure

• Hair's curliness is determined by the disulfide bonds within the hair shaft. Cysteine amino acids hold together the keratin protein which makes up 65 to 95 percent of the hair. These bonds are strong yet flexible, giving strands elasticity and resilience.
  
  

Significance

• Keratin treatments are expensive and semi-permanent, with the stick-straight results lasting from one to three months. Women are willing to undergo the expense and some discomfort associated with the process because hair can appear less damaged than with relaxers, thermal straightening, flat ironing or blow-outs.
  
  

Ingredient

• Formaldehyde or its derivatives are commonly found in keratin treatments. Formaldehyde is also found in many cosmetics, but a concentration higher than 0.2 percent in keratin treatments may be harmful to the skin, hair and overall health, according to a product review at Cosmeticsinfo.org.
  
  

Controversy

• Although many keratin treatment manufacturers state that the keratin is what causes hair to become straight, health experts and some beauty professionals believe it's actually the potent formaldehyde content, according to CBSNews.com. Keratin is incapable of breaking hair's disulfide bonds needed to restructure the hair into a straight form.
  
  

Potential

• Keratin treatments can be performed by professionals or at home. One at-home treatment is a hydrolized keratin spray which takes 30 minutes to process before brushing hair straight. Results last 30 to 45 days.