Hair coloring


Hair coloring, or hair dyeing, is the practice of changing the hair color. The main reasons for this are cosmetic: to cover gray or white hair, to change to a color regarded as more fashionable or desirable, or to restore the original hair color after it has been discolored by hairdressing processes or sun bleaching.
Hair coloring can be done professionally by a hairdresser or independently at home. Today, hair coloring is very popular, with 75% of women and 18% of men living in Copenhagen having reported using hair dye. At-home coloring in the United States reached $1.9 billion in 2011 and was expected to rise to $2.2 billion by 2016.

History

, a Greek historian, described in detail how Celtic people dyed their hair blonde:
"Their aspect is terrifying... They are very tall in stature, with rippling muscles under clear white skin. Their hair is blond, but not naturally so: they bleach it, to this day, artificially, washing it in lime and combing it back from their foreheads. They look like wood-demons, their hair thick and shaggy like a horse's mane. Some of them are clean-shaven, but others—especially those of high rank—shave their cheeks but leave a moustache that covers the whole mouth...".
The dyeing of hair is an ancient art that involves treatment of the hair with various chemical compounds. In ancient times, the dyes were obtained from plants. Some of the most well known are henna, indigo, Cassia obovata, senna, turmeric and amla. Others include katam, black walnut hulls, red ochre and leeks. In the 1661 book Eighteen Books of the Secrets of Art & Nature, various methods of coloring hair black, gold, green, red, yellow, and white are explained. The development of synthetic dyes for hair is traced to the 1860s discovery of the reactivity of para-phenylenediamine with air. Eugène Schueller, the founder of L'Oréal, is recognized for creating the first synthetic hair dye in 1907. In 1947 the German cosmetics firm Schwarzkopf launched the first home color product, "Poly Color". Hair dyeing is now a multibillion-dollar industry that involves the use of both plant-derived and synthetic dyes.

Application techniques

Off-scalp

Hair color was traditionally applied to the hair as one overall color. The modern trend is to use several colors to produce streaks or gradations, but not all work on top of a single base color. These are referred to as:
There are also newer coloring techniques such as ombré, in which hair is dark on the crown and bit by bit becomes lighter toward the ends.
These are off-the-scalp techniques, and can be applied by the following methods:
All coloring techniques can be used with any type of color. For lightening, the hair sometimes has to be bleached before coloring.

On-scalp

Hair coloring can also be applied on the scalp for a more solid level of coverage
All coloring techniques can be used with any type of color. For lightening, the hair sometimes has to be bleached before coloring.

Types

The four most common classifications are permanent, demi-permanent, semi-permanent, and temporary.

Permanent

Permanent hair color generally contains ammonia and must be mixed with a developer or oxidizing agent in order to permanently change hair color. Ammonia is used in permanent hair color to open the cuticle layer so that the developer and colorants together can penetrate into the cortex. The developer, or oxidizing agent, comes in various volumes. The higher the developer volume, the higher the "lift" will be of a person's natural hair pigment. Someone with dark hair wishing to achieve two or three shades lighter may need a higher developer whereas someone with lighter hair wishing to achieve darker hair will not need one as high. Timing may vary with permanent hair coloring but is typically 30 minutes or 45 minutes for those wishing to achieve maximum color change.

Demi-permanent

hair color is hair color that contains an alkaline agent other than ammonia and, while always employed with a developer, the concentration of hydrogen peroxide in that developer may be lower than used with a permanent hair color. Since the alkaline agents employed in demi-permanent colors are less effective in removing the natural pigment of hair than ammonia these products provide no lightening of hair's color during dyeing. As the result, they cannot color hair to a lighter shade than it was before dyeing and are less damaging to hair than their permanent counterpart.
Demi-permanents are much more effective at covering gray hair than semi-permanents, but less so than permanents.
Demi-permanents have several advantages as compared with permanent color. Because there is essentially no lifting 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; and they wash out over time, so root regrowth is less noticeable and if a change of color is desired, it is easier to achieve. Demi-permanent hair colors are not permanent but the darker shades in particular may persist longer than indicated on the packet.

Semi-permanent

permanent hair coloring involves little or no developer, hydrogen peroxide or ammonia, and is thus less damaging to hair strands. The reduced amount of developer, whether peroxide or ammonia, means that hair previously damaged by applying permanent color or permanent reshaping is less likely to be damaged during the color application process.
Semi-permanent hair color uses compounds of lower molecular weight than are found in temporary hair color dyes. These dyes penetrate the hair shaft only partially, because of the reduced amount of developer used. For this reason, the color will survive repeated washing, typically 4–5 shampoos or a few weeks, before undergoing significant fading or washing out entirely.
Semi-permanents may still contain the suspected carcinogen p-phenylenediamine or other related colorants. The U.S. Environmental Protection Agency reported that in rats and mice chronically exposed to PPD in their diet, the PPT appears to simply depress body weight of the animals, with no other clinical signs of toxicity observed in several studies.
The final color of each strand of hair will depend on its original color and porosity. Because hair's color and porosity across the head and along the length of a hair strand, there will be subtle variations in shade across the entire head. This gives a more natural-looking result than the solid, all over color of a permanent color. Because gray or white hairs have a different starting color than other hair, they will not appear as the same shade as the rest of the hair when treated with semi-permanent color. If there are only a few grey/white hairs, the effect will usually be enough for them to blend in, but as the gray spreads, there will come a point where it will not be disguised as well. In this case, the move to permanent color can sometimes be delayed by using the semi-permanent as a base and adding highlights.
Semi-permanent color cannot lighten the hair.

Temporary color

Temporary hair color is available in various forms including rinses, shampoos, gels, sprays, and foams. Temporary hair color is typically brighter and more vibrant than semi-permanent and permanent hair color. It is most often used to color hair for special occasions such as costume parties and Halloween.
The pigments in temporary hair color are high molecular weight and cannot penetrate the cuticle layer. The color particles remain to the surface of the hair shaft and are easily removed with a single shampooing. Temporary hair color can persist on hair that is excessively dry or damaged in a way that allows for migration of the pigment to the interior of the hair shaft.

Alternative color

Alternative hair coloring products are designed to create hair colors not typically found in nature. These are also referred to as "vivid color" in the hairstyling industry. The available colors are diverse, such as the colors green and fuchsia.
Permanent alternatives in some colors are available. More recently, blacklight-reactive hair dyes have been brought to market that fluoresce under blacklights, such as those often used at nightclubs.
The chemical formulae of alternative color dyes typically contain only tint and have no developer. This means that they will only create the bright color of the packet if they are applied to light blond hair. Darker hair would need to be bleached in order for these pigment applications to take to the hair desirably. Some types of fair hair may also take vivid colors more fully after bleaching. Gold, yellow and orange undertones in hair that has not been lightened enough can muddy the final hair color, especially with pink, blue and green dyes. Although some alternative colors are semi-permanent, such as blue and purple, it could take several months to fully wash the color from bleached or pre-lightened hair.

Maintaining hair color

There are many ways that people can maintain their hair color, such as:
Hair coloring involves the use of chemicals capable of removing, replacing, and/or covering up pigments naturally found inside the hair shaft. Use of these chemicals can result in a range of adverse effects, including temporary skin irritation and allergy, hair breakage, skin discoloration and unexpected hair color results. According to the International Agency for Research on Cancer, in vitro and in vivo studies have shown that some hair dyes and many chemicals used in the hair dyeing process can be considered mutagenic and carcinogenic.

Skin irritation and allergy

In certain individuals, the use of hair coloring can result in allergic reactions and/or skin irritation. Individuals allergic to gluten for example, will need to be cautious when purchasing hair color since certain hair dye includes gluten. Gluten does not need to be ingested for it to cause an allergy. Skin contact with gluten may cause a reaction; therefore, leading to an allergy. Symptoms of these reactions can include redness, sores, itching, burning sensation and discomfort. Symptoms will sometimes not be apparent immediately following the application and processing of the tint, but can also arise after hours or even a day later.
To help prevent or limit allergic reactions, the majority of hair color products recommend that the client conduct a patch test before using the product. This involves mixing a small quantity of tint preparation and applying it directly to the skin for a period of 48 hours. If irritation develops, manufacturers recommend that the client not use the product.
European dermatologists have, however, strongly advised against such pre-use testing, as it entails additional sensitisation risk and the interpretation by lay people may not be sufficiently accurate.

Skin discoloration

Skin and fingernails are made of a similar type of keratinized protein as hair. That means that drips, slips and extra hair tint around the hairline can result in patches of discolored skin. This is more common with darker hair colors and persons with dry absorbent skin. That is why it is recommended that latex or nitrile gloves be worn to protect the hands.
This discoloration will disappear as the skin naturally renews itself and the top layer of skin is removed. Ways of preventing skin discoloration are to wear latex or nitrile gloves to protect the hands and also by applying a thin layer of petroleum jelly or oil-based preparation around the hairline. Gentle abrasives such as moist baking soda or a small amount of toothpaste applied with a toothbrush may also help remove the uppermost layer of skin and dye. Acetone and nail polish remover are not considered effective; laundry detergent may sometimes work as may moist cigarette ash rubbed into the stained area.

Unintended results

Several factors influence the final color of the hair following the coloring process.
In October 2017, the leading breast surgeon Professor Kefah Mokbel published a meta-analysis showing that use of hair dyes might increase the risk of developing breast cancer by 20% among users.

Chemistry of permanent hair coloring

Permanent hair coloring requires three components: 1,4-diaminobenzene or 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 diimine with a coupler compound.
3) Oxidation of the resulting compound to give the final dye.
The preparation is in the leuco form. Oxidizing agents are usually hydrogen peroxide, and the alkaline environment is usually provided by ammonia. The combination of hydrogen peroxide and ammonia causes the natural hair to be lightened, providing a "blank canvas" for the dye. Ammonia opens the hair shaft pores so that the dye can actually diffuse inside the fiber. These dye intermediates and coupler compounds can undergo oxidation and coupling reaction as shown in the scheme below to form high molecular weight products, which are trapped in the hair matrix and cannot be readily removed through washing.
Various combinations of primary intermediates and coupler compounds provide a spectrum of shades of hair colors. The primary intermediates are aromatic para compounds, such as 1,4-diaminobenzene or 4-aminophenol. The coupler compounds are meta-substituted derivatives of aniline. They come in three major classes based on the color that they produce when they react with the primary intermediate.

The first step shows the oxidation of p-phenylenediamine to the quinonediimine :
This species exists in equilibrium with the monoprotonated form . The second step involves the attack of this quinonediimine on the coupler. In organic chemistry, this reaction is called electrophilic aromatic substitution:
In the third and final step, the product from the quinonediimine-coupler reaction oxidizes to the final hair dye.
It was once believed that the dye forms in the above reaction bonds to hair permanently. It was later shown that the main reason that this reaction imparts a permanent color on hair by producing larger dye molecules, which is locked inside the hair.

Plant-based dyes

is an orange dye commonly used as a deposit-only hair color whose active component, lawsone, binds to keratin. It is therefore considered semi-permanent to permanent, depending on a person's hair type. Most people will achieve a permanent color from henna, especially after the second dye. With repeated use the orange color builds up into red and then auburn. While "natural" henna is generally a red color, variations exist. These variations usually contain ingredients from other plants and even synthetic dyes.
Indigo is natural dye from a plant that can be added to henna or layered on top of it to create brown to black colors in the hair. Henna is orange, and indigo is blue, so as complementaries on a standard color wheel, the two colors' combined effect is to create brown tones. Like henna, indigo may fade after one application, but it becomes permanent on the hair with repeated use.
Using a plant-based color such as henna can cause problems later when trying to do a perm or permanent hair color. Some store-bought henna contains metallic salts which reacts to hydrogen peroxide that is used in hair lightening. This may lead to unpredictable results, such as green or blue tones in the hair. Henna is a healthy way to color hair, as long as no metallic salts are used.
In 2018, a system for making semi-permanent hair dyes from renewable waste blackcurrant fruit skins from the fruit pressing industry was developed. Anthocyanin pigments were extracted from the blackcurrant skin waste and formulated into hair dyes. The dyes showed high buildup on hair and gave an intense blue color, which was stable to multiple washes.

Legal restrictions

Hair dyes are cosmetic compounds that make contact with the skin during application. Because of this skin contact, there exists some health risk associated with use of hair dyes. Thus, hair dyes are regulated in the commercial marketplace and, as new toxicity data is generated for some hair dyes and health risks are discovered, some of these hair dyes are being legally restricted from the cosmetic marketplace.
The European Union is particularly stringent with regard to health regulations. To ensure that hair dyes contain only safe substances, the European Commission adopted the Directive 2012/21/EU to restrict the use of around 45 chemicals in hair dyes. The directive on dyes is part of a general and comprehensive set of regulations, the EU Cosmetics Directive 76/768/EC.

Religion

For Muslims, if a man is not of advanced age, there is no harm in his using black dye. Some of the early Muslims, including some sahabah, permitted the use of black dye. As narrated in a hadith, the best thing with which to dye gray hair is henna and katm.