Hair Color

 

Hair coloring is the process of adding color to or removing color from the hair shaft. Hair coloring process may be referred to as coloring or bleaching, depending on whether we are adding or removing color to our hair. Most common reasons are to cover gray hair, to change to a color regarded as more trendy, and to restore the original hair color.

Our hair color is the pigmentation of hair follicles due to two types of melanin namely Eumelanin and Pheomelanin. Normally, if more melanin is present, the color of the hair is darker; if less melanin is present, the hair is lighter. Levels of melanin can vary over time causing a person's hair color to change. It is likely to have hair follicles of more than one color in a person.

There are mainly three kinds of Hair colors available in the market. They are, 

1. Temporary Hair Color.  

2. Semi Permanent Hair Color.

3. Permanent Hair Color.

Temporary Hair Color :

Temporary hair color plainly coat the hair shaft with pigments which later wash off. Temporary hair colors may deposit acidic dyes onto the outer surface of the hair shaft or might consist of some pigment molecules that can slip inside the hair shaft, using a small amount of peroxide or none at all. Shampooing will eventually dislodge temporary hair color. These products don't contain ammonia, meaning the hair shaft isn't opened up during processing and the hair's natural color is retained once we washout our hair.

Semi-permanent hair Color :

Semi-permanent hair color has smaller molecules than temporary colors, and is therefore able to partially break in the hair shaft. For this cause, the color will survive repeated washing, typically 4–5 shampoos or a few weeks. Semi-permanents colors contain nil, or very low levels of developer, peroxide or ammonia, and are therefore safer for damaged or fragile hair. However, semi-permanents may still contain the toxic compound p-phenylenediamine or other such ingredients.

Semi-permanents have several advantages as compared with permanent color. Because there is essentially no lifting (i.e., removal) of natural hair color, the final color is less uniform/homogeneous than a permanent and therefore more natural looking; they are gentler on hair and therefore safer, especially for damaged hair.

Permanent Hair Color :

Practically all permanent hair colors use a two-step process (usually occurring concurrently) which first removes the original color of the hair and then deposits a new color. It's essentially the same process as lightening, except a colorant is then bonded within the hair shaft. Ammonia is the alkaline chemical that opens the hair cuticle and allows the hair color to penetrate the cortex of the hair. It also acts as a catalyst when the permanent hair color comes together with the peroxide. Peroxide is used as the developer or oxidizing agent. The developer removes pre-existing color. Peroxide breaks chemical bonds in hair, releasing sulfur, which accounts for the characteristic odor of hair color. As the melanin is decolorized, a new permanent color is bonded to the hair cortex. Various types of alcohols and conditioners may also be present in hair color. The conditioners close the cuticle after coloring to seal in and protect the new color. 

Mechanism of Action of Hair Color :

The most popular way to achieve permanent hair coloring is through the use of oxidation dyes. The ingredients of these products include 2,5-diaminotoluene a coupling agent, and an oxidant. The process is typically performed under basic conditions.

The mechanism of oxidation dyes involves three steps:

 1) Oxidation of 1,4-diaminobenzene derivative to the quinone state.
 2) Reaction of this diamine with a coupler.
 3) Oxidation of the resulting compound to give the final dye.

Oxidizing agents are usually hydrogen peroxide, and the alkaline environment is generally provided by ammonia. The blend of hydrogen peroxide and the primary intermediate causes the natural hair to be lightened, which provides a blank canvas for the dye. Ammonia opens the hair shaft so that the dye can actually bond with the hair, and ammonia speeds up the reaction of the dye with the hair.

Most permanent color changes require that the cuticle of the hair be opened so the color change can take place within the cuticle. This process, which uses chemicals to alter the structure of the hair, can damage the cuticle or internal structure of the hair, leaving it dry, weak, or prone to breakage. After the hair processing, the cuticle may not fully close, which results in coarse hair or an accelerated loss of pigment. Generally, the lighter the chosen color from one's initial hair color, the more damaged it may be. 

Bleaching :                          

Bleach is used to lighten hair color. The bleach reacts with the melanin in hair, removing the color in an irreversible chemical reaction. The bleach oxidizes the melanin molecule. The melanin is still present, but its oxidized molecule is colorless. However, bleached hair tends to have a pale yellow tone. The yellow color is the natural color of keratin, the structural protein in hair. Also, bleach reacts more readily with the dark eumelanin pigment than with the phaeomelanin, so some gold or red residual color may remain after lightening. Hydrogen peroxide is one of the most common lightening agents. The peroxide is used in an alkaline solution, which opens the hair shaft to allow the peroxide to react with the melanin. Bleaching has the side effect of raising of the cuticle, making the hair more porous.

When you bleach your hair, some of your natural pigment will stay. Even though people believe that if you bleach your hair, you can apply any color and it will come out how the color swatch looks. This is not always the case. Since some of your natural pigment stays, it mixes with the color base you are applying and can some times cause, well, a funky color. If you've ever-turned green or orange, you know what I mean!

Common Hair Colorant Ingredients & Their Functions :         

Component	Function	Ingredients
Solvent	Dye vehicle	Water, Propylene glycol, Ethanol, Glycerin
Surfactant	Foaming, thickening	Sodium lauryl sulfate, Ceteareth-25, Cocoamide MEA, Oleth-5
Alkali	Swell hair	bleaching Ammonia, Monoethanolamine
Buffer	Stabilize, reproducible	Disodium phosphate, Citric acid.
Dye precursors	Impart color	P-Aminophenol, 1-Naphtol, P-Phenylenediamine, 4-Amino-2-hydroxytoluene
Fatty alcohols	Emollients	Glyceryl stearate, Cetearyl alcohol
Quaternary compounds	Conditioning	Polyquaternium, Cetrimonium chloride
Peroxide, Oxidant	bleaching	Hydrogen peroxide

How Safe is Hair Color :

Cancers develop due to a combination of many factors damaging the DNA of a cell in the body. Many studies have been conducted to try to determine whether long-term hair dye use causes cancer, and it is still a controversial subject. Most studies have focused on a possible increased risk of bladder cancer. Some studies have found that women who had consistently used hair dye long term had higher levels, and other studies did not. Many official bodies have determined that the evidence so far is inconclusive.

However, new studies have linked hair dye use to development of a specific type of cancer, non-Hodgkin's lymphoma (Zhang et al, 2008). This study looked at groups of women suffering from this disease, and a control group. It was found that women who started using hair dye, particularly darker colors, before 1980 had an increased risk of developing the disease.

The strongest evidence that hair dyes can cause cancer in humans comes from studies of cancer rates in hairstylists. One study found that if a hairstylist had used hair dyes at work for 5 years or more, she had a three times higher risk of developing breast cancer. Other studies have consistently found that hair colorists have an increased risk of non-Hodgkin's lymphoma, multiple myeloma and leukemia.
Studies have shown that hair stylists have higher rates of skin allergies, asthma and breast cancer.

"Hair coloring is a personal decision for all kinds of reasons. But if you are the person, if semi-permanent or temporary dyes could serve your purpose, You should do it. Because these contain much less of the ingredients linked to cancer."