Because I'm a Nerd

As I posted earlier in the week, I went to the Holiday Open House/Beauty Show hosted by our local State Beauty Supply this past Monday.  CHI was there and explained how their products use MEA as the alkalizing ingredient rather than ammonia.  One of the benefits of using MEA in their system rather than ammonia is that you can perm or texturize and color in the same day.  I wanted to learn more about MEA and knew that just because it was different didn't mean it was damage-free.  I believe all permanent hair color lines have some drawbacks; heck,  it is chemically changing your hair so there are going to be some issues and I am interested to learn about how hair color works on a molecular level so I was cruising the internet looking for information.  Here is an article I came across on P&G's website that I found interesting.  I hope you like it too.

http://www.pgbeautygroomingscience.com/chemistry-at-a-glance.html

You are in: Home » Research & Development » Publications » Research Update Archive » Hair Color Research Update » Chemistry At-a-Glance

Chemistry At-a-Glance

Oxidative Dye Formulas

Most oxidative dye formulations contain two or more ingredients that act as dye precursors or couplers, essential ingredients common to most permanent dyes. They generally consist of p-diamines and p-aminophenols. Precursors are oxidized to active intermediates when they have penetrated the hair shaft. Intermediates then react with ingredients called color couplers to create wash-resistant dyes. Couplers modify the color produced by the oxidation of precursor compounds.

A conventional oxidative colorant is made up of two components which are mixed together directly before application to the hair.

• DyePrecursor/Alkalizer/Thickening System—This component contains several ingredients, each with different functions. They are packaged together because they are completely compatible with each other and must be kept away from the oxidizing agent (hydrogen peroxide). 
• The first component is an alkalizing agent (usually ammonia and/or an ammonia substitute such as monoethanolamine [MEA]). This has a number of roles in the hair colorant process:
• Swelling the hair fiber to aid in diffusion of the dye precursors
• Raising the hair's internal pH and ensuring that the overall dye mix has a high pH
• Facilitating the formation of the dyes within the hair fiber and catalyzing melanin bleaching
• The second component is a mixture of dye precursors. These are the ingredients that react together within the hair fiber, resulting in the formation of color.
• The third is a surfactant (and optionally polymer) thickening system that provides the solubilization of the first two components (particularly the dyes) and, when mixed with the H₂O₂ component (below) provides the final viscosity to hold the product on the hair fibers without mess and dripping into the eyes, and if applicable, is tailored to work optimally with any application or mixing device supplied with the product.
• Hydrogen Peroxide Oxidant—It is essential that this component be kept at a low pH for storage to ensure stability; but it is only at high pH that bleaching and dyeing occurs. This component may also contain polymers or surfactants that thicken when mixed with the high pH tint, and/or provide conditioning and rinsing benefits when the combined dye mass is rinsed from the hair. Hydrogen peroxide plays the following roles:
• A source of oxidizing agent for catalyzing the reaction of dye precursors
• Dispersing and solubilizing the hair's natural pigment, melanin, while bleaching the hair's natural pigment and any previous artificial colorant present in the hair fiber

Once these components are mixed and applied to the hair surface, two complementary processes take place: bleaching the hair's natural pigment and other artificial pigments present in the hair, and diffusion of dye precursors into the hair, followed by coupling reactions that result in the formation of chromophores within the hair fiber, which are then too big to diffuse out of the hair. The end result achieved results in the balance of these two processes, the mixture of dye precursors, the initial hair color and hair quality.

More complex colors may contain several precursors and many couplers, and involve multiple reactions. To create each shade in the hair coloring spectrum,
formulators must become artisans, assessing which developers and couplers to combine, how much of each to use, and the ratio and total concentration of the
various intermediates.

How Coloring Alters Biology

Hair is protected by a covalently bound, mono-molecular layer of unique branched fatty acid - 18 methyl eicosanoic acid (18-MEA). 18-MEA, often referred to as the f-layer, is the fatty lipid layer that binds to the surface of the cuticle and acts as the hair's natural conditioning system. Because the f-layer has a natural lubricating
mechanism and is water repellent, it gives each hair fiber a built-in conditioning system that reduces damage caused by blow-drying and brushing.^{14, 15}  

f-Layer of a hair follicle

During permanent coloring, the combination of hydrogen peroxide, ammonia and high pH removes some of the protective f-layer, causing additional oxidation of the hair surface and some irreversible physiochemical changes in hair fibers. Repeated coloring can cause this protective surface to completely disappear. As a result, the hair becomes hydrophilic (water loving) instead of hydrophobic (water repellent), and the natural lubricating properties are removed. Hair is more susceptible to damage, feels dry and is hard to detangle. It looks duller and less colorful, and requires more conditioning.

Free Radical Formation—EDDS Addresses The HO* Radical

Most hair color users understand that by its nature, permanent color makes irreversible changes to hair structure. The bleaching and oxidation action chemically alter hair proteins, lipids and pigments. While pigment changes are desirable, the changes to proteins and lipids can cause hair to be more susceptible to damage. Most consumers adapt to these changes by using conditioners to protect hair and limiting hair color application to once every 4-6 weeks.

However, what they may not know is that not all the damage done by hair colorants is necessary. There are two key reactive species in current permanent hair color: the perhydroxyl anion (HOO-) and the HO* radical. The HOO- species is the species intentionally put in by manufacturers. While it has some damaging side effects, it is the species that is responsible for the desired changes to hair color. The HO* radical, however, is an undesired by-product of a reaction between H₂0₂ and metal ions. It does not contribute to the development of color but does contribute to hair damage. The elimination of this unnecessary free radical can significantly reduce hair damage without compromising hair colorant performance. One approach to reducing the free radical is to eliminate the exposure to metal ions. Metal ions come into the hair through exposure to water. Studies show that protein damage, as measured by formation of cysteic acid, is significantly reduced by elimination of copper in tap water.

Suppression of Free Radical Formation The suppression of free radical formation can be visualized microscopically by comparing gas production from a formulation containing no EDDS chelant (0.1% EDTA)  s. one containing EDDS (1% level). Signifi cantly fewer gas bubbles can be seen being formed in the sample treated with EDDS - clearly demonstrating the ability of EDDS to reduce the gas formation signifi cantly.

Gas Formation after 10 min., no EDDS

Gas Formation after 10 min., with EDDS

Addressing the HO* Radical

Recently, hair color scientists discovered a way to reduce damage from the HO* radical, blocking its formation with the use of chelants—molecules that can coordinate metals through multiple binding sites. They added EDDS (ethylenediaminedisuccinic acid), a chelant which is highly selective to copper, to home hair coloring kits. During the coloring process, EDDS binds to the copper, preventing access to the copper by hydrogen peroxide, which results in better color formation and less damage. The preference of the EDDS for copper over calcium makes it superior to traditional chelants, such as EDTA or DTPA, and more efficient at preventing fiber damage.

A 5-cycle repeat test showed that EDDS prevents more than 95 percent of radical damage. After-care conditioners, which water-proof hair, additionally help prevent damage and copper absorption as color ages. By minimizing free radical damage, advances such as EDDS help hair remain resilient and retain a healthy, lustrous look.¹⁷