As stated in the text Progressive brush using formaldehyde, O formaldehyde use in treatments that promise to straighten hair it's totally forbidden for the Anvisa (National Health Surveillance Agency) and constitutes a heinous crime. The use of glutaraldehyde or glutaral is also prohibited for this purpose, due to its chemical similarity with formaldehyde, presenting the same risks and restrictions.
But now there is another substance that is gaining a lot of fame in beauty salons, promising to straighten the hair without causing any harm to the person. it is about the carbocysteine. Is this really true?
Well, carbocysteine is a substance based on amino acids and vegetables, it is derived from the amino acid L-Cysteine, one of the amino acids that make up our hair's natural keratin. The formulas for cysteine and carbocysteine are shown below:
Cysteine and Carbocysteine Formulas
The shape of the hair depends on the combination of forces that act on the keratin, among these forces are the sulfur bridges (disulfide bridges).
Disulfide bridges in hair
To break these bridges and thus make it possible to change the shape of the hair, a reducing agent, like the thioglycolic acid or thiol-acetic acid (HS ─ CH2 ─ COOH), releasing the protein strands:
Sulfur bridge separation process carried out by thioglycolic acid
Then you need a oxidizing agent to regenerate the sulfur bridges, but in the new format, with new positions.
Thus, carbocysteine acts similarly to thioglycolic acid (thioglycolate), breaking sulfur bridges. But it is important to emphasize that she alone cannot straighten her hair as promised, an oxidizing agent is also needed. And that's where the danger lies, because to achieve this desired effect, some formulas mix glyoxylic acid and even formaldehyde into the formula as oxidizing agents. In this way, some customers end up being deceived, and the risks are the same.
The dryer and flat iron are used very hot because the heat applied helps in the oxidation process.
The heat from the flat iron is used in the progressives to help with oxidation
Furthermore, these oxidation processes are favored at basic pH, but carbocysteine is carried in a very acidic formulation. Thus, if it is used in treatments without the harmful products mentioned, it won't straighten your hair, but it can help reduce volume, moisturize and shine. Some hair that is not as wavy may even, over time, get a smoother effect.
Another important fact is that any brush called "progressive", "smart", "chocolate", and so on, is not regulated by the Anvisa. But there are some specific active substances with smoothing properties, like thioglycolic acid, sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide and guanidine hydroxide, which are allowed by legislation.
Carbocysteine is not included among these substances, as is glyoxylic acid, which means that there may be associated risks that have not yet been researched.
So, so that you are not deceived with miraculous promises and take care of your hair safely, ask the professional who will perform the technique show you the packaging of the product that will be used and see if it is registered with Anvisa through the following link: Anvisa / Cosmetic Consultation.
Another point that is important to remember is that all chemical processes bring some kind of damage to the hair, and this is also done by carbocysteine, as she can change the hair color. It can cause the breakdown of strand keratin amino acids, such as tryptophan, cystine and methionine, appearing yellowish in color. Blond hair can turn egg yellow and red hair can turn orange.
If the hair is already dyed, the change in color can be even greater, as the hydrogen peroxide used for Discolor the strands decompose easily, releasing oxygen atoms that break down the proteins in the hair. Thus, bleached hair already has active sites, having, consequently, a much greater degree of degradation.
If carbocysteine degrades and cystyl radical formation occurs, hair can turn green! This does not happen in all cases, but unfortunately there is this risk.
By Jennifer Fogaça
Graduated in Chemistry
Source: Brazil School - https://brasilescola.uol.com.br/quimica/escova-carbocisteina.htm