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16 December 2014

Colour to dye for: how much do we really know about the risks of colouring our hair?

The basic chemistry of hair dyes has changed little over the last century, but what do we know about the risks of colouring our hair, and why do we do it?

By Rebecca Guenard

Every two months Barclay Cunningham goes through a process that begins with taking an antihistamine tablet. After a few hours, she smears a thick layer of antihistamine cream across her forehead, around her ears and over her neck. Finally, she shields the area with ripped-up plastic carrier bags.

All this so she can dye her hair.

It didn’t start out this bad. Cunningham coloured her hair for a decade without any problems. Then, one day, she noticed that the skin on her ears was inflamed after she’d dyed her hair. She fashioned plastic bag earmuffs and carried on colouring. But the allergic reaction persisted, so her precautions became more elaborate. Now if she dyes her hair without these measures, she gets an itchy, blistery, pus-filled rash that lasts for weeks.

Suffering for the sake of tinted tresses is not a modern-day phenomenon. Humans have dyed for thousands of years, experimenting with ever-changing, often vicious, formulas to achieve a new hair colour.

The chemical history of modern hair dyes reveals that, while they were once part of an innovative industry, progress has stalled, and today they rely on antiquated methods. But consumers are not exactly pressuring the industry to innovate. Not when they are so desperate to change their hair colour that they’re willing to discreetly pick scabs from their hair, as Cunningham does, for weeks after colouring.

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Aesthetic tendencies drift with marketing and cultural currents, but our drive to alter ourselves is a constant. As anthropologist Harry Shapiro wrote: “So universal is this urge to improve on nature…that one is almost tempted to regard it as an instinct.” 

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Hundreds of plastic practice mannequins, lips pursed in proper model pouts, float around the halls of the Energizing Summit, an annual event of the American Board of Certified Haircolorists. You don’t really ever adjust to seeing the disembodied heads, be they upside down in clear plastic bags (the handle cinched tight around the neck for easier carrying), gazing out of boxes in the hotel lobby, or mounted on poles, like some kind of punishment from Tudor England.

Hairdressers from around the USA, all with stunning hair colour and impeccably maintained roots, criss-cross the poorly lit basement of the Marriott Hotel at Los Angeles Airport. They’re here for two days of sessions dedicated to the science of dyeing hair.

Right away I realise that I have a lot to learn. Hair colourists, it seems, speak a different language to the rest of us. They talk of “volume” (concentration) and “lift” (lightening). And it turns out I have been making a faux pas. “We dye Easter eggs,” one Summit instructor gently informs me. “We colour hair.”

But after a day and a half, I am still waiting for some science. Then I find Tom Despenza. He has years of experience working in research and development at Clairol – a career that began when, as a microbiology student, his car broke down in front of a beauty school. He is now retired and owns his own hair colour company called Chromatics.

When I catch up with Tom at the Summit, he has been teaching his popular class “Forget the Hype! Let’s get real”, which dispels the years of hearsay that makes up the beauty school curriculum.

Understanding the dyes used on hair is not as simple as understanding the colour wheel. As we all learned in art class, any colour can be obtained by mixing the three primary colours of red, yellow and blue. If you want orange, you mix yellow and red; if you want purple, you combine red and blue; and if you want brown, you mix all three.

Beauticians are taught the same thing when it comes to hair – that brown dye is a combination of three different dyes. “That’s just fictitious information,” says Despenza. “Brown hair colour is made up of two chemicals.” Both chemicals are colourless, he explains, but they produce brown through a chemical reaction that occurs when they’re combined.

An important distinction exists between colour and dye. Hairdressers are not applying pigments (at least not in the case of permanent hair dye), they are applying a mixture of chemicals to initiate dye formation. The individual dye molecules have to be linked together before they emit colour, so dyes have to sit on the head for 30 minutes to allow this reaction to occur. 




In the mid-1800s, English chemist William Henry Perkin serendipitously synthesised the first non-natural dye: starting with coal tar, he was hoping to produce the malaria drug quinine but instead created mauve. His discovery revolutionised the textile industry and launched the petrochemical industry. Natural dyes just didn’t have the staying power and vivid colours of the dye Perkin created. Never before had such a steadfast dye been found.

Soon after, August Hofmann (Perkin’s chemistry professor) noticed that a dye he had derived from coal tar formed a colour when exposed to air. The molecule responsible was para-phenylenediamine, or PPD, the foundation of most permanent hair dyes today.

Although hair is a protein fibre, like wool, the dyeing process for textiles cannot be duplicated on the head. To get wool to take a dye, you must boil the wool in an acidic solution for an hour. The equivalent for hair is to bathe it in the chemical ammonia. Ammonia separates the protective protein layers, allowing dye compounds to penetrate the hair shaft and access the underlying pigment, melanin.

Melanin is what gives colour to human skin, eyes and hair. It’s the ratio of two types of melanin – eumelanin and pheomelanin – that determines your natural hair colour. And it’s the size and shape that the melanin molecules form when they cluster in the hair shaft that gives the unique tones within a hair colour. For example, blondes and brunettes have about the same ratio of eumelanin molecules to pheomelanin molecules, but blondes have fewer molecules overall. Natural blond hair also contains smaller melanin clusters, which reflect light more than the larger clusters found in dark hair.

Along with ammonia, hair dye formulas contain hydrogen peroxide, a bleaching agent. Peroxide serves two purposes: it reacts with the melanin in hair, extinguishing its natural colour, and provokes a reaction between PPD molecules. The trapped colour-emitting molecule will remain in the hair, too big to escape, and the natural colour will appear only as the hair grows out.

Early on, dye chemists realised that if they added a secondary molecule, called a coupler, they could manipulate the chemicals – a carbon here, a couple of nitrogens there – and multiply the colour choices that were available with PPD alone. Different methods have been proposed, but beauty manufacturers have yet to accept a permanent hair colour formula without PPD or its related compound p-aminophenol.




For 125 years, the oxidative reaction of PPD has been the extent of hair dye technology. Dr David Lewis, emeritus professor at the University of Leeds in the UK, thinks that this is “crazy”. “Now, I know a lot about dyes and dye stuffs in the textile industry. We would never dream of using this on textiles,” he says. “Primitive, archaic, all these things come to mind. Why do they persist on putting it on human heads?”

As a research professor, Lewis acted as a consultant for cosmetics companies, but he always felt uncomfortable about their insistence upon using the same old oxidative formulas. Lewis retired from academia ten years ago to launch Green Chemicals, a company that aims to develop safer consumer goods. His company introduced a more environmentally friendly flame retardant, and now Lewis wants to overhaul hair dyes.

One issue is how dyes work: Lewis says that the colour molecules become electron scavengers along the way to creating beautiful brown tresses. This need for electrons is not fulfilled exclusively by other dye molecules, so the electron scavengers also aggressively pursue the skin – causing allergic reactions and potentially damaging DNA.

Lewis is also worried that the beauty industry has too much power over consumer safety. The modern era of the Food and Drug Administration (FDA) began in 1906, when it was known as the Bureau of Chemistry. In 1930 it adopted the name we know today. The FDA has banned many types of dyes since, but it has always officially deemed coal tar dyes safe, especially for hair colouring, as long as consumers were warned of the possibility of skin irritation. To this day, coal tar dyes (which are now derived from petroleum) do not require FDA certification.

In 1979 the FDA tried to insist that hair dye manufacturers place the following label on their products: “Warning – Contains an ingredient that can penetrate your skin and has been determined to cause cancer in laboratory animals.” The ingredient referred to is 4-MMPD, 4-methoxy-m-phenylenediamine, a dye with a structure very similar to PPD that, according to the FDA, showed sufficient scientific evidence of being carcinogenic. Manufacturers disagreed and threatened to sue the FDA if they pressed for the label. The FDA backed down. A few years later, manufacturers removed the carcinogenic compound from their formulas, while maintaining that 4-MMPD was safe.

There is some research into the potential risk of dyes. In 2001, researchers at the University of Southern California published a paper in the International Journal of Cancer concluding that women who frequently dye their hair were twice as likely to develop bladder cancer than those who abstain. The European Commission on Consumer Safety took note. A panel of scientists evaluated the paper, deemed it scientifically credible and recommended that the EU reassess hair dye regulations.

Over the past decade the Science Committee on Consumer Products (SCCP) – a committee of the European Commission mandated to assess and report on product safety – has collected and evaluated manufacturers’ data and published opinions on a number of hair dye ingredients. This re-evaluation of hair colour ingredients by the EU has highlighted two issues.

The first is that sensitisation to dye chemicals has grown considerably. The EU has categorised 27 hair colour ingredients as sensitisers, listing 10 of them as extreme and 13 strong. Although the first exposure to a sensitiser might have no noticeable effect, a subsequent exposure – to the same chemical or to similar chemicals in temporary tattoos or textiles, for example – could lead to an allergic reaction. In the worst case, it could trigger anaphylaxis, an extreme and potentially fatal allergic response.

The second issue is a lack of data on what dye chemicals do inside the human body. When in doubt, the European Commission bans the use of a particular chemical. In 2006, then-European Commission Vice-President Günter Verheugen said in a press release: “Substances for which there is no proof that they are safe will disappear from the market. Our high safety standards do not only protect EU consumers, they also give legal certainty to European cosmetics industry.” It has prohibited 22 hair dye chemicals so far – and more are likely to be added to the list, which is updated annually. Most recently the SCCP deemed 2-chloro-p-phenylenediamine, used to colour eyebrows and lashes, unsafe on the grounds of insufficient toxicology data.

When the SCCP released the findings on sensitivity in early 2007, Colipa (the European cosmetic trade association, now known as Cosmetics Europe) published a statement to “reinforce its confidence in the safety of hair dyes”. Although stating their support of the European Commission’s ongoing work to evaluate the safety of hair dyes, they argued that the dye chemicals were being tested in isolation and that the findings did not give an indication of the health risks the chemicals could pose if used in consumer products as instructed.

Scientists working for the industry continue to point out that no undisputed epidemiological studies show a significant risk of cancer among people who colour their hair. Unless you look at a population that is exposed to hair dye every day: hairdressers. Hairdressers have a 5 per cent greater chance of contracting bladder cancer than the general population. 

It struck me that there was no mention of the safety of hair dye chemicals during any of the instructional classes I attended at the Energizing Summit. When I overheard a student being advised to think about her long-term health as a hairdresser, I looked up to see whether it related to contact with dyes (studies have shown that wearing gloves greatly reduces the amount of dye compounds absorbed into the body). But it turned out that the student was being counselled on her wrist position, not the use of gloves.




In the 1970s, anthropologist Justine Cordwell wrote a paper entitled “The very human arts of transformation”. In it, she wrote: “The anthropological analysis of clothing and adornment should be based on the assumption that mankind, from earliest times, has probably regarded the human body as the primary form of sculpture – and not been particularly pleased with what he has seen.”

Indeed, archaeological evidence shows that the use of dyes by humans dates back to the Palaeolithic period. Early humans used the iron oxide contained in dirt to decorate their dwellings, textiles and bodies with the colour red. It wasn’t too long until they applied the dyes to their heads.

Ancient Egyptians dyed their hair, but rarely did so while it was on their heads. They shaved it off, then curled and braided it to fashion wigs to protect their bald heads from the sun. Black was the most popular colour until around the 12th century BCE, when plant material was used to colour the wigs red, blue or green, and gold powder was used to create yellow.

Of natural dyes, henna endures. The ancients also used saffron, indigo and alfalfa. But natural dyes only coat the hair temporarily, and people wanted chemically altered tresses. Analysing hair samples has revealed that the Greeks and Romans used permanent black hair dye thousands of years ago. They mixed substances that we know today as lead oxide and calcium hydroxide to create a lead sulphide nanoparticle, which forms when the chemicals interact with sulphur linkages in keratin, a protein in hair. When the direct application of lead proved too toxic, the Romans changed their black dye formula to one made by fermenting leeches for two months in a lead vessel.

Prostitutes during the early years of the Roman Empire were required to have yellow hair to indicate their profession. Most wore wigs, but some soaked their hair in a solution made from the ashes of burnt plants or nuts to achieve the colour chemically. Meanwhile, Germans coloured their hair red by applying a mixture of beechwood ash and goats’ fat.

With the development of the scientific method in the early modern period, dyers took a more analytical approach to changing hair colour, testing the efficacy and safety of new formulas. Delights for Ladies, a recipe book of household essentials published in the early 1600s, recommends using Oyle of Vitrioll to colour black hair chestnut. The book cautions to avoid touching the skin – sound advice given that today we know Oyle of Vitrioll as sulphuric acid.

The fashion for Italian blondes repeated itself – as hair colour trends do – several hundred years later when, in the 1700s, Venetian women would recline in the sun on specially built terraces with their hair drenched in corrosive solutions of lye to achieve golden locks. Blond hair was no longer limited to prostitutes.

Yet dyes were used for more than fashion or to signify occupation. Cordwell identifies several instances where hair colour was changed for other reasons; for example, Afghans believed that dyeing their hair red with henna could cure a bad headache.




Beauty is a multi-billion-pound industry that’s continuing to grow. According to one industry report, cosmetics manufacturing will have brought in $255bn (£155bn) in revenue globally in 2014. The industry remained stable through the recession and, as incomes increase with recovery, demand for high-priced beauty products means that global profits are estimated to increase to $316bn by 2019.

Globally, haircare products are the largest portion of the beauty industry and secure nearly a quarter of industry revenue. In the USA, within hair and nail salons, hair-colouring services account for 18 per cent of revenue. An estimated 70 per cent of women in the USA use hair colouring products.

Reflecting on the heritage of hair dyes, you can’t help but ask: why do so many people still colour their hair? Why would someone go through the rigmarole and tolerate the expense, the itching and the smell? Whatever drives our desire to change the colour of our hair, one thing is certain: people have deep emotional ties to what covers their scalps.

This is clearly true for Barclay Cunningham. At just 12 years old, she began experimenting with her hair, using a spray-in hair-lightening chemical. As an adult, she searched for years for the right hair colour. “Never once has it occurred to me to simply not dye my hair,” Barclay says. “The ‘me’ of hair colour happens to come out of a box. The ‘me’ that grew out of my head was not right.” 


© Luke Evans

Blond without the bottle

Exploring how a small change in your DNA sequence can make you a natural blonde.

A few weeks after preparing them, Dr Catherine Guenther checked her mouse embryos and knew that she had identified the source of a blond-haired mutation in human DNA. The not-yet-fully-formed mice looked like tiny Portuguese men o’ war – bulbous, translucent and speckled blue at the edges.

Guenther copied sequences of human DNA near a gene called KITLG. She fused the sequence with another piece of DNA that encodes for an enzyme and injected the linked pieces into mouse embryos, which incorporated the DNA in their chromosomes.

When Guenther inspected the embryos closely she could see the enzyme’s blue precipitate within their hair follicles, leading her to conclude that the DNA sequence she added played a crucial part in hair follicle development. “I showed the embryos to Dr Kingsley before I went home that day and we were very excited,” says Guenther. “We had proven that there was a hair follicle control element in this region that could be different between blondes and brunettes in Northern Europeans.” 

The human molecular factory in charge of colouration churned out the same edict for hundreds of thousands of years: make pigment! Then, at some point, the product diversified. To adapt to less sunlight as early humans moved into higher latitudes, the genes of our ancestors adjusted melanin density in the skin. With less ultraviolet-absorbing melanin, humans could make much-needed vitamin D from sunlight penetrating the skin.

But no one knows exactly when or why humans began to display variation in hair and eye colour. One theory focuses on the high population of fair-haired people in northern Europe and presumes that during the Ice Age, an imbalance of women to men drove the development of unique hair and eye colour that would catch the attention of a potential mate. The human molecular factory simply required a decrease in melanin production to impose such a monumental evolutionary effect.

Guenther works as a research scientist in the lab of Dr David Kingsley at Stanford University. The Kingsley lab studies human evolution, seeking to answer questions about how humans came to be, well, human.

In 2007, collaborating scientists in Iceland and the Netherlands published a paper describing how they had scanned the genome for variants associated with human pigmentation and found 60 distinct areas where a one-letter change in the genetic code resulted in lighter skin, eyes or hair. One of these single-nucleotide polymorphisms (SNPs), as they are called, resided near the KITLG gene.

The Kingsley team pored over genetic data repositories, searching for places in the genetic code near the KITLG gene that tell the gene what to do. They found a location in the DNA where proteins known as transcription factors bind to the sequence and carry out the instructions specified in the code.

They discovered that if the nucleotide guanine holds that spot, the transcription factor cannot bind as tightly to the DNA as when another nucleotide (adenine) is in the same position. This simple alteration – replacing A with G in the DNA sequence – reduces the expression of the gene and, ultimately, changes the colour of the hair.

Guenther’s blue-flecked mice prove that the Kingsley group found the spot on the genome that informs hair follicles how much melanin to incorporate into hair.

Next, the group wanted to know what would happen if they gave mice one set of KITLG instructions versus another – one set reading ‘make a blond mouse’, and the other reading ‘create a brunette’. Reproducibly, the mouse given the blond variant has lighter-toned fur than the mouse with the brunet variant.

So if we understand the precise genetic origin of such a trait, can we manipulate our genes to achieve a desired appearance? Could humans, for example, inject the DNA sequence for the blond variant and override the instructions to make brunet hair? If only it were so simple. Researchers have identified more than 12 chromosomal regions associated with hair colour so far, including regions in eight genes associated specifically with blond hair. Furthermore, the KITLG gene serves in more than one location. “I think hair dye is going to be around for a while,” says Guenther.


© Luke Evans

Down the drain

What do we know about the environmental impact of hair dye chemicals?

In the 1990s, environmental researchers first started collecting evidence showing that even at negligible concentrations, the pharmaceutical and personal care products we use daily interfere with the ecosystem.

Today, an increasing number of micropollutants are being identified in rivers around the world. The list of substances regularly detected in waterways includes anti-inflammatories, antibiotics, antidepressants, plasticisers and surfactants. And each year a research scientist or concerned citizen points out an emerging contaminate that has yet to be considered: the most recent examples include artificial sweeteners and fuel additives.

It is a daunting task to keep track of the vast amount of chemicals we use and dispose of into the environment. But in the past 20 years, most nations have incorporated micropollutant monitoring in their environmental assessments. In the USA, a previously unconsidered potential contaminant might gain attention through the U.S. Geological Survey (USGS), an organisation of scientists and technicians in hundreds of locations throughout the country that evaluate its natural resources.

“We are looking at rivers. We’re looking at wastewater – treated and untreated. We are looking at brackish water in wetlands. We are looking at ground water. We are looking at potable and nonpotable. We are looking at produced waters that come up from energy production,” says Alex Demas, public affairs specialist for the USGS.

The USGS has compiled a list of more than 2,500 constituents identified in North American waters. The list is so long because it includes compounds that are naturally occurring, like methane, and compounds that appear in minuscule quantities of little concern. The USGS ranks the constituents into three tiers to prioritise the chemicals that need focused monitoring. Tier 1 compounds require the most attention because they exist in higher quantities and their chemistry causes harm to aquatic life.

The USGS constituent list contains a group of chemicals that could be present in waterways as a result of hair dye disposal. The compounds are ranked Tier 1 owing to their regular occurrence during monitoring; one compound that could be a metabolite of hair colour was found at 79 per cent of urban sites the USGS monitored.

The uncertainty here results from the fact that there are no available data on how hair dyes break down after they enter the environment. How are they affected by the disinfection process at sewage and drinking water plants? How are they metabolised by algae and other aquatic life? What by-products do they leave behind?

These questions are important because metabolites can often be more toxic than parent compounds. Unfortunately, they are often formed in an effort to produce clean drinking water. Before water comes to the tap, it passes through a treatment facility where oxidisers, such as chlorine, are added to the water to kill pathogens and provide a potable water supply.

Dr Ching-Hua Huang, Professor of Environmental Engineering at Georgia Tech University, specialises in disinfection by-products, especially compounds called nitrosamines. “We found that if you have some secondary amines and you put chlorine for oxidation, you will unintentionally generate nitrosamines in your finish water,” says Dr Huang.

David Lewis, a dye chemist and founder of Green Chemicals, proposes that hair dyes – chemically classified as secondary amines – can form these highly carcinogenic compounds after disposal. Nitrosamines exhibit toxicity even at the lowest concentrations, and they induce cancer at exposures of only a part per trillion. Huang agrees with Lewis that the secondary amines used as hair dyes could form stable nitrosamines.

The USGS prioritises the nitrosamine N-nitrosodiphenylamine as a Tier 1 compound because it has been detected periodically in water and sediment. But there is no way to know whether this compound, or any of the potential derivatives of dye chemicals listed as constituents by the USGS, can be linked to the disposal of excess hair colour until research scientists approach the problem from the front end. Someone must study the fate of these compounds in the environment, starting with their trip down the drain.   


© Luke Evans

Why do we dye?

Jemima Hodkinson explores what drives so many of us to colour our hair.

“Is it true… blondes have more fun?” Advertising for hair dye has played on our follicular insecurities since the 1950s, when Clairol slogans like this helped make hair dye seem more accessible – and acceptable – for every girl next door to use. By 1969 so many American women were using hair dye that the ‘hair colour’ field was removed from US passports. Why are advertising messages like these – and their modern equivalents – so successful at convincing us to buy these products? What drives us to change our natural hair colour?

Of course, humans have toyed with the keratin on their heads for millennia: a 2,000-year journey from goats’ fat and burned nutshells, via vitriol and lead, to Casting Crème and Sun-In. The significance and popularity of particular hair colours have varied between groups, generations and periods, but the intrinsic properties of hair might help us to explain why we are so attached to our monthly touch-ups and why hair colouring is a multi-billion-dollar industry.

According to Rose Weitz, sociologist and author of the book, Rapunzel’s Daughters: What women’s hair tells us about women’s lives, the significance of hair and hair colour in our lives rests on two factors – its malleability and its highly personal quality – that make it “uniquely suited for conveying symbolic meanings”.

Added to this, hair is one of our most public bodily commodities, visible and open to interpretation by others at a second’s glance. These essential factors are equally true for men and women – but Weitz believes that they are of greater importance for women, given that “women still are often evaluated based on their appearance”.

One view supported by Weitz is that hair is just another part of our bodies that we change to project a particular identity. The stereotypes surrounding particular hair colours are strong, and dyeing our hair may be rooted in a conscious or unconscious desire to identify with these stereotypes: feisty redheads, feminine blondes, nonconformist rainbow Mohican-wearers.

Although the associations between particular hair colours and traits are strong, they change through generations, and trends shift as a result. Even the widely accepted – and researched – idea that blond hair enhances female sexual attractiveness may be more recent than we think. Weitz argues that generations of western culture have associated blond hair with childhood and purity rather than sex appeal, with darker hair symbolising passion. Evidence for this crops up in the blond locks of virgins in Christian art and in fairy tales, where golden-haired heroines embody goodness and innocence. Look further back, and the connotations of blondness change again: Roman prostitutes could be identified by their dyed yellow hair.

However, many die-hard dye users are seeking to reverse the natural changes in hair colour associated with age, rather than assuming a completely different hair colour. Again, this aversion to ageing hair has not always been the case. Before the 20th century, when hair dye was even more unpleasant and short-lasting, there was far less stigma attached to grey hair.

As Weitz explains, “older women were expected to have grey hair, and those who dyed their hair risked ridicule if this was discovered”. However, the ‘cult of youth’ that gathered momentum over the 20th century was reflected in the increasing stigma surrounding grey hair for women and a boom in popularity of new, safer dye products.

Now, the bottle of Nice ’N Easy is seen by some women as an important tool in the workplace, allowing them to sidestep the stigma attached to ageing by camouflaging its signs. Of the 20 current female US senators, all aged between 46 and 81, none have (visible) grey hair. The male senators – those who still have hair – sport varying shades of grey, white and salt-and-pepper. Time magazine described this as a “great unspoken iniquity [that] officeholders don’t dare publicly discuss…for fear of seeming trivial”.

The culture surrounding hair colour continues to change, even if the chemistry behind it hasn’t moved on much since the 1950s. Increasingly, men around the world are using dye to wash away the grey. In 2007, the Wall Street Journal reported the growing role of hair dye in Chinese politics, where “the dye job appears to have become as commonplace as the Mao suit once was”.

Unlike many other male world leaders, 61-year-old Chinese president Xi Jinping sports a full head of black hair. Some have speculated that this boom in dye use among the upper echelons of Chinese society is due to China’s youthful demographics: 4 in 5 citizens are under 55. As such, age is seen as a major factor in promotions at work, and perhaps men reach for the dye bottle in an attempt to retain their chances of advancement as well as their youthful looks. It might also have other beneficial side-effects: manufacturers suggest that men dye their hair for the “bedroom and the boardroom”.

The chemical concoctions that change our hair colour can have a remarkably strong effect on our lives; they can help us in comply with the expectations of a youth-obsessed society, identify with a particular stereotype or try to remain afloat in a cutthroat corporate world. Unsurprisingly, the hair dye market shows little sign of shrinking.         

This package was first published in Mosaic. It is republished here under a Creative Commons licence.