Hair coloring

A hairdresser colors a client's hair.
Woman with colored hair

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, 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 over 75% of American women dyeing their hair.[1] At home coloring in the United States reached $1.9 billion in 2011 and is expected to raise to $2.2 billion by 2016.[2]

History

Portrait of Lafayette in 1830, aged 73, with pitch-black hair.

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.[3] Some of the most well known are henna (Lawsonia inermis), indigo, Cassia obovata, senna, turmeric and amla. Others include katam, black walnut hulls, red ochre and leeks.[4] 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.[5] The development of synthetic dyes for hair is traced to the 1860s discovery of the reactivity of para- phenylenediamine (PPD) with air.[6] Eugène Schueller, the founder of L'Oréal, is recognized for creating the first synthetic hair dye in 1907.[7] In 1947 the German cosmetics firm Schwarzkopf launched the first home color product, "Poly Color".[8] Hair dyeing is now a multibillion-dollar industry that involves the use of both plant-derived and synthetic dyes.[9]

Application techniques

Off-scalp

Hair with blonde highlights

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, not all work on top of a single base color. These are referred to as:

These are off-the-scalp techniques, and can be applied by the following methods:

All application techniques can be used with any type of color. For lightening, the hair will sometimes have to be bleached before coloring.

On-scalp

Hair coloring can also be applied on the scalp for a more solid level of coverage

All application techniques can be used with any type of color. For lightening, the hair will sometimes have to be bleached before coloring.

Types

The four most common classifications are permanent, demi-permanent (sometimes called deposit only), semi-permanent, and temporary.[6]

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, in permanent hair color, is used to open the cuticle layer so that the developer and colorants together penetrate into the cortex.[11] 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 a high developer. Timing may vary with permanent hair coloring but is typically 30 minutes or 45 minutes for those wishing to achieve maximum gray coverage.

Demi-permanent

Demi-permanent hair color is hair color that contains an alkaline agent other than ammonia (e.g. ethanolamine, sodium carbonate) 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 (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; and they wash out over time (typically 20 to 28 shampoos), 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

Semi-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 low 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 (PPD) 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.[12]

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 adsorbed (closely adherent) 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

Hair and beard colored blue.

Alternative hair coloring products are designed to create hair colors not typically found in nature. The available colors are diverse, such as the colors green and fuchsia. Permanent alternatives in some colors are available. Some color shades are blacklight-reactive, and thus show up under certain nightclub lighting, for instance.

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. People with darker hair (medium brown to black) need to use a bleaching kit before tint application. Some people with fair hair may benefit from prior bleaching as well. Gold, yellow and orange undertones in hair that has not been lightened enough can adversely affect results, especially with pinks, blues and greens. 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 these:

Natural hair coloring alternatives

There are many natural ways to color the hair instead of having to use color that contains several chemicals especially, some that may cause irritation to the skin. A lot of the natural hair coloring can be simply done at home. Natural hair coloring alternatives can be done by the use of natural herbs such as henna. Different types of herbs can be used to achieve a certain color. Indigo or black walnut powder lead to a black or dark color and chamomile and calendula lead to a darker blond. Teas such as black or hibiscus that are made from black tea leaves and hibiscus flowers are also natural ways to color the hair, henna and derivatives are also used for hair coloring, especially in South East Asia, to achieve a dark Orange-reddish hue. Although many of the natural hair coloring can be done at home, there are products on the market that come as a kit that can be purchased or salons that use natural ingredients in their hair color.

Note that even though these are natural ways to color the hair, it is still important to wear gloves because dye is being worked with.

Adverse effects

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 (IARC), in vitro and in vivo studies (in exposed human populations) have shown that some hair dyes and many chemicals used in the hair dyeing process can be considered mutagenic and carcinogenic.[13][14]

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 (allergy) risk and the interpretation by lay people may not be sufficiently accurate.[15]

Hair breakage

Hair that has been damaged by excessive exposure to chemicals is considered over-processed. This results in dry, rough and fragile hair. In extreme cases, the hair can be so damaged that it breaks off entirely. The main cases of hair breakage are: Lack of moisture and oils, poor diet, stress, over processing or illness.

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 (typically takes a few days or at most a week). 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. There are also products that come in wipes or liquid form at beauty supply stores to remove hair dye from skin.

Unintended results

Several factors influence the final color of the hair following the coloring process.

Health concerns

Chemistry of permanent hair coloring

Permanent hair coloring requires three components: (1) 1,4-diaminobenzene (historically) or 2,5-diaminotoluene (currently), (2) a coupling agent, and (3) an oxidant. The process is typically performed under basic conditions. The mechanism of oxidation dyes involves three steps:[6] 1) Oxidation of 1,4-diaminobenzene derivative to the quinone state. 2) Reaction of this diimine with a coupler compound (more detail below). 3) Oxidation of the resulting compound to give the final dye.

The preparation (dye precursors) is in the leuco (colorless) 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 (couplers) 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.

Couplers are chemical compounds that define the color of the hair dye. Shown here are three red couplers (A, B, C), two yellow-green couplers (D, E) and a blue coupler (F).

The first step shows the oxidation of p-phenylenediamine to the quinonediimine (C6H4(NH)2):

This species exists in equilibrium with the monoprotonated form (C6H4(NH)(NH2)+) (not shown). 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.[6] 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.[25]

Plant-based dyes

Henna 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 (Indigofera tinctoria, suffructicosa, or arrecta) 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.

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.[26] 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.[27] The directive on dyes is part of a general and comprehensive set of regulations, the EU Cosmetics Directive 76/768/EC.

See also

References

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  2. Holmes, Elizabeth. "Sales of Boxed Hair Color Rise as Shoppers Look To Save Time and Money; Shouldn't It Be Easier By Now?". The Wall Street Journal.
  3. Corbett, J. F. Hair Colorants: Chemistry and Toxicology; Micelle Press: Dorset, U.K., 1998; Thompson, R. H. "Naturally Occurring Quinones" Academic Press: New York, 1957.
  4. BBC. "BBC - Radio 4 Woman's Hour -The History of Hair Dye".
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  10. Wilson, Cynthia (6 August 2012). "Dip-Dye Hair Coloring Tutorial and Styles". Womenio. Retrieved 6 October 2012.
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  12. p-Phenylenediamine, U.S. Environmental Protection Agency
  13. "IARC working group on the evaluation of carcinogenic risks to humans: occupational exposures of hairdressers and barbers and personal use of hair colourants; some hair dyes, cosmetic colourants, industrial dyestuffs and aromatic amines. Proceedings. Lyon, France, 6-13 October 1992.". IARC Monogr Eval Carcinog Risks Hum. 57: 7–398. 1993. PMID 7911535.
  14. IARC Monographs Working Group on the Evaluation of Carcinogenic Risks to, Humans (2010). "Some aromatic amines, organic dyes, and related exposures.". IARC monographs on the evaluation of carcinogenic risks to humans / World Health Organization, International Agency for Research on Cancer. 99: 1–658. PMC 5046080Freely accessible. PMID 21528837.
  15. Thyssen, Jacob P.; Søsted, Heidi; Uter, Wolfgang; Schnuch, Axel; Giménez-Arnau, Ana M.; Vigan, Martine; Rustemeyer, Thomas; Granum, Berit; McFadden, John (2012-06-01). "Self-testing for contact sensitization to hair dyes--scientific considerations and clinical concerns of an industry-led screening programme". Contact Dermatitis. 66 (6): 300–311. ISSN 1600-0536. PMID 22568836. doi:10.1111/j.1600-0536.2012.02078.x.
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  19. Lamb, James (Feb 1997). "Reproductive toxicology. Lead acetate trihydrate.". Environ Health Perspect. 105: 315. doi:10.2307/3433461.
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  21. DeNoon, Daniel J. (January 26, 2004). "Hair Dye Linked to Blood Cancer: Long-Term Use of Dark, Permanent Dye May Raise Lymphoma Risk". Web MD. Retrieved 2007-07-29.
  22. 1 2 Hair Dye Linked to Blood Cancer. Webmd.com. Retrieved on 2010-12-21.
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  25. Alexander Chan, Sean Kung, (September, 2006), "Hair Colorant Technology Advances Further", Personal Care, p. 11-16
  26. Swati Maiti, Sudarson Sekhar Sinha and Mukesh Singh, "Hair Dye-DNA Interaction: Plausible Cause of Mutation", Cosmetics 2015, 2(4), 313-321; doi:10.3390/cosmetics2040313
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