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home / 世界杯决赛2022

the right chemistry: seems like a good time to brush up on hair dyes

when the pandemic closed salons, some critics of the cosmetics industry welcomed a decline in exposure to the chemical ppd.

by joe schwarcz, special to the montreal gazette
published aug 12, 2020
read time 4 minute read
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read time 4 minute read
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“now we will find out what people’s natural hair colour is.” that joke scooted around the blogosphere after hair salons were forced to close down in response to covid-19. however, not everyone was dismayed by the reduction in the use of hair dyes. critics of the cosmetics industry pointed out various concerns that had been raised over the years about para-phenylenediamine (ppd), a common ingredient in permanent hair dye formulation. they welcomed a decline in exposure to this chemical.para-phenylenediamine first came to the public’s attention in 1933 at the chicago world’s fair where a dramatic exhibit by the food and drug administration caught the eye of visitors. on display were pictures of women who had suffered eye damage, and in one severe case, blindness, after having used “lash lure,” an eyelash and eyebrow dye. the exhibit was stimulated by a couple of recent reports in the journal of the american medical association (jama) that described severe eye injuries after the use of products that contained ppd. at the time, there were no regulations pertaining to cosmetics and manufacturers had no obligation to test their products for safety. fda had long been clamouring for a change to the food and drug act of 1906, the only regulatory legislation in existence that had little teeth and ignored cosmetics. the world’s fair exhibit was designed to bring to the public’s attention the dangerous consequences of a lack of proper regulations.the display received a boost in publicity when first lady eleanor roosevelt visited and exclaimed “i cannot bear to look at them” on seeing the pictures. a reporter quickly dubbed the exhibit “the american chamber of horrors.” the public got further wind of what was going on when paramount released a newsreel including footage of the corneal damage suffered by women using the “eyelash beautifier.” the film did not identify the product as lash lure, which led to maybelline, manufacturer of a competing product, to protest vigorously to paramount. they complained that although their product contained no ppd, their reputation and sales had been damaged because they had used “eyelash beautifier” in their advertising. maybelline actually used coal dust mixed with vaseline, an idea that came from mabel, the sister of the company’s founder.in 1934, another paper appeared in jama, this time documenting the death of a woman after her eyebrows had been completely plucked and then replaced by the dye. it seemed that the ppd had caused a severe allergic reaction, irritating the skin and allowing bacteria to enter, causing sepsis. in those pre-antibiotic days, such infections were often fatal. president franklin d. roosevelt was a strong proponent of public health and in 1938 managed to have congress pass the food, drug and cosmetic act that prohibited the use of ppd in eye cosmetics but allowed its use in hair dyes, where it can be found to this day.para-phenylenediamine was first synthesized in 1854 from the coal-tar chemical aniline by german chemist august wilhelm von hofmann. it is unclear to what extent von hofmann investigated the properties of the chemical, but we know that in 1883, the french company p. monnet et cie was granted a patent for its use as a dye. when ppd is exposed to oxygen in air, it forms a number of compounds ranging in colour from dark brown to black. since hydrogen peroxide releases oxygen, combining it with ppd speeds up the development of colour. this proved to be valuable in the fur trade and by the late 1800s ppd was also being used to dye hair. results were not always satisfactory since the colour washed out too easily.researchers eventually found that when ppd is mixed both with hydrogen peroxide and a “coupler” before being applied to the hair, a reaction takes place that produces a dye, but only once the chemicals have been absorbed into the hair shaft. the coloured molecules formed are too large to diffuse out of the hair, hence the term “permanent.” “temporary” or “semi-permanent” dyes do not contain ppd.para-phenylenediamine is a documented allergen, which of course is an issue, but there is also concern that it may be a carcinogen. the “sister study” published in 2019 surveyed a large cohort of american women who had a sister with breast cancer but were cancer-free themselves. it found an increased risk of cancer with permanent dye use, especially in black women. a previous study by the rutgers school of public health in 2017 looked at some 4,000 women, half of whom had breast cancer, and came to a similar conclusion. of course, such associations cannot prove cause and effect due to confounding factors such as diet and the use of other personal care products such as hair-relaxers that can contain formaldehyde.although there is no proven link between breast cancer and permanent hair dyes, researchers are looking at alternative formulations that eliminate ppd. polydopamine can mimic natural melanin in hair, and anthocyanins derived from black currents also have potential. in any case, the risk, if any, from permanent hair dyes is small, and there is also something to be said for being happy about what you see in the mirror.joe.schwarcz@mcgill.cajoe schwarcz is director of mcgill university’s office for science & society (mcgill.ca/oss). he hosts the dr. joe show on cjad radio 800 am every sunday from 3 to 4 p.m.note to readers: all our coronavirus-related news can always be found at montrealgazette.com/tag/coronavirus.sign up for our email newsletter dedicated to local covid-19 coverage at montrealgazette.com/coronavirusnews.help support our local journalism by subscribing to the montreal gazette here.
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