Serendipitious: The first artificial hair dye was developed by a chemist who set out to make an anti-malarial drug from coal tar. (Luke Evans)

'I want dyed hair – even if I have to pick scabs off my scalp'

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

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.

Long history
Suffering for the sake of tinted tresses is not a modern-day phenomenon. Humans have dyed their hair 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, although 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 scalp, as Cunningham does, for weeks after colouring.

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."

Science of dyeing hair 
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 in Los Angeles. 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 Despenza 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.

Colour vs dye
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 nonnatural 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 was a precursor of 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.

Active ingredients
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 few of nitrogens there – and multiply the colour choices 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.

Same old formulas
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 United Kingdom, thinks 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 in 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 on using the same old oxidative formulas. Lewis retired from academia 10 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) in the United States 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 are 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."

To dye for: Researchers at the University of Southern California concluded that women who frequently dye their hair were twice as likely to develop bladder cancer than those who did not.(Ronaldo Schemidt/AFP)

Potential risks
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, but continued to maintain 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, which concluded 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 European Union reassess hair dye regulations.

Over the past decade the Science Committee on Consumer Products – 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 as 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 the European cosmetics industry." The commission has prohibited 22 hair dye chemicals so far – and more are likely to be added to the list, which is updated every year. Most recently, the Science Committee on Consumer Products deemed 2-chloro-p-phenylenediamine, used to colour ­eyebrows and lashes, unsafe because of insufficient toxicology data.

Risk of cancer
When the Science Committee on Consumer Products 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 for 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% 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.

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

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

Suffering for beauty
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."

This story first appeared on Mosaic and has been edited for the Mail & Guardian. A longer, online version of this story can be found at http://mosaicscience.com/story/hair-dye 

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colourUniversity of Leeds