How do Brazilian keratin treatments really work?

What's in there?

Although it seems nearly impossible to get accurate and complete ingredient lists for these products, most of them do seem to contain similar general types of ingredients.

  • Keratin protein, obtained from sheep's wool or other sources, usually hydrolyzed into lower molecular weight polypeptides as well as amino acids
  • An aldehyde or aldehyde precursor of some sort (formaldehyde, vanillin, bioformyl, glyoxal biformal)—forms a reversible bond with cysteine (prominent amino acid in hair keratin)
  • Conditioners — fatty alcohols, cationic polymers (such as polyquaternium-7, amodimethicone), silicones (amodimethicone, dimethicone, dimethiconol, cyclic silicones), lanolin
  • Polymers and biopolymers (such as collagen)
  • Preservatives, fragrances
  • Metallic nanoparticles (gold, copper) — unique to QOD Cosmetic products, the metal nanoparticles catalyze the reaction in a manner similar to the aldehydes (possibly)

How does it work?

When a client first comes into the salon to receive a keratin smoothing treatment, the technician or assistant will wash her hair to make sure the surface is free of contaminants or chemicals from styling products. Then a liquid solution will be applied to the hair. This solution contains keratin, as well as other ingredients, such as conditioning agents, aldehydes or other catalysts, preservatives, etc.. The hair is then blown dry and straightened using a flat iron on very high heat (450°F is the recommended temperature).

Most of the formulas contain a formaldehyde solution called formalin. (MSDS for Formalin (37% Formaldehyde solution, with methanol)) Some of the current products use other aldehyde molecules, while yet others claim to be "aldehyde-free." I could find no descriptions in the scientific literature of the mechanism by which this product works. I had to dig through biochemical and biomedical literature to get some clues, and think I arrived at a possible mechanism. I am wading in with my chemistry high boots on, and this is more of an educated guess than anything.

Aldehydes readily react with amino acids, especially cysteine, a sulfur-containing amino acid prevalent in both human hair keratin as well as in keratin derived from other species. This is known in organic chemistry as a Schiff-Base reaction. This technique has been used in the preparation of biological samples for electron microscopy study. Formaldehyde and other aldehydes in the human body can crosslink proteins and DNA and through a complicated series of reactions can transform protein structures into what is known as advanced glycation products (AGE). These AGE products are undesirable and are responsible for inflammation and other diseases in the body, so it is interesting that someone thought to exploit this reaction in a way that would be advantageous and would hopefully have no deleterious effects.

When these keratin treatment solutions are applied to hair, the aldehydes react with cysteine found in both the keratin solution and also with the hair. This creates crosslinks between hair keratin and product keratin and holds them together in a semi-permanent fashion. The bonds do not last forever though, and are gradually broken and the keratin is washed away in the shower, which allows the hair to return to its pre-treatment state.

The smaller polypeptides and amino acids of the hydrolyzed keratin penetrate the cuticle and help to plump the hair and fill in gaps. The larger-molecular-weight portions form a film on the surface of the hair and are held there by the crosslinks. The high-temperature flat-ironing process straightens the hair and locks in the new straighter conformation as well as seals the cuticle and the keratin film on the surface.

The distributors of products that make the claim to be aldehyde-free are not very forthcoming with ingredient lists or mechanistic discussions regarding how their product works. Thus, I can only speculate that their products work in a similar manner to the ones with known aldehydes in them.

Early processes required the client to not get their hair wet for 4 days post-treatment and also required them to avoid deforming their hair in any way by wearing a hat, barrette, or even pushing it behind an ear. Some current treatments allow a much more flexible schedule than this, and a return to normal activity and grooming may be as soon as the next day.

Aftercare is quite specific as well, in that clients are admonished to never use any sulfate or sodium ion-containing shampoo or other products on their hair. Many salons offer a package of approved products for an additional (usually quite hefty) sum. I hypothesize that sodium ions dissolve the complex that holds the keratin to the hair, and thus causes the effects to rapidly erode and possibly leads to damaged or frizzy hair. If this is the case, I wonder if they have considered the effects a water softening system would have? The high sodium content in softened water would surely be as damaging as using a product with sodium in it.

As far as the heat goes, I have to say that temperatures that high can be incredibly damaging to hair. It causes water inside the hair to actually boil, which can cause ruptures in the hair shaft itself, leading to breakage and split ends. With the remarkable results reported by many, one can only assume that not everyone is as susceptible to this hazard as some. However, there are also many, many reports of people experiencing significant breakage and hair loss at the root. Some people have lost up to 60% of their hair after receiving this treatment. My concerns about this product type is that there seems to be insufficient testing and data at this time to fully understand how to achieve a consistent result.

I do not wish to gloss over the formaldehyde/aldehyde issue, but this article is already very long. I plan to delve more into that topic next month. I will say though that testing has found the levels of formaldehyde in these products to exceed the maximum levels approved by OSHA for exposure. Formaldehyde is a dangerous, carcinogenic substance and should not be taken lightly. I would like to explore this and the other aldehydes in more depth next month.

  • 3 of 4
Tonya McKay

Tonya McKay Becker is a curly-haired polymer scientist and cosmetic chemist whose academic and industrial research experience have provided her with expertise in the fundamentals and applications of polymer science and colloid chemistry. She has long had a fascination with the structure-property relationships of the complex solutions used in hair and skin care products, and how they interact with and impact these remarkable biological substrates. Ever curious, Tonya has dedicated herself for more than a decade to honing her expertise on the science of curly hair, how it differs from straight hair, and how product ingredients used on curly hair affect its health and beauty. Her passion for sharing this knowledge with others has led to her current career of educating people from all backgrounds who share an interest in this exciting field.