'Do or dye? Do blondes have more fun? At what cost? Before you head back to the beauty salon, read up on chemistry and complexities of colouring your hair.
Clairol, of course, did not invent the idea of colouring hair. Early Egyptians already used an extract of the henna plant to impart red or orange highlights, and the Romans made a black hair dye by boiling walnut shells and leeks. But it wasn't until chemists learned how to synthesize novel compounds from coal tar that truly effective dyes were developed.
Eugene Schueller, a French chemist, is credited with creating the first commercial hair dye. Back in 1909, he came up with a basic formulation. It was very similar in concept to the one used today, in that it included para-phenylenediamine (PPD), ammonia, and hydrogen peroxide. He then founded the French Harmless Dye Company, which a year later was more attractively renamed as L'Oreal. Schueller included "harmless" in the name because the coal tar dyes that had been used for fifty or so years to colour fabrics had already developed a reputation for toxicity. In truth, he had no evidence at all that his concoction was harmless, and claims that PPD and its chemical relatives can have an adverse effect on health have plagued the hair dye industry ever since.
The dye that Schueller created can be referred to as a "permanent dye" because it survives numerous shampooings. Today's permanent dyes are certainly superior to Schueller's, but the basic chemistry is the same. The outside layer of a hair shaft, known as the cuticle, is made of a network of overlapping cells that can be likened to a Venetian blind. For chemicals to seep into the underlying layer, the cortex, where the hair pigments are to be found, the "blind" has to be opened. This is where ammonia comes in. It swells the hair and opens the cuticle so that hydrogen peroxide and the other dye components can get to the cortex. Here, the peroxide gets down to work. Its first role is to disrupt some of the chemical bonds found in eumelanin and phaeomelanin, the natural pigments responsible for black to brown and red to yellowish hair respectively. These molecules have a variety of carbon-carbon double bonds that can absorb certain wavelengths of light and therefore determine the color of hair. Hydrogen peroxide reacts with these double bonds and the altered pigments then reflect most wavelengths of light and the hair appears much lighter. "Peroxide blondes" like Marilyn Monroe owed some of their fame to the marvels of hydrogen peroxide.
But in a permanent dye, this destruction of melanin is just step one. As the cuticle opens up, molecules that are the building blocks of the eventual dye diffuse in to the cortex. There are two distinct species. One, referred to as the "primary," is exemplified by the phenylenediamines, and the other, often an aminophenol, is known as the "coupler." These compounds are stable and do not react with each other until they are mixed with hydrogen peroxide. Once inside the cortex, reaction occurs and primary and coupler join to form a coloured molecule that is now too large to escape through the slats of the "Venetian blind." It is permanently locked into the hair! The exact colour depends on which specific primary and which coupler are used. Primaries are usually p-phenylenediamines or p-aminophenols while couplers are resorcinols, m-aminophenols, m-phenylenediamines, or napthols. Want a nice shade of blue hair? Then you'll need to couple m-phenylenediamine with p-phenylenediamine. A combo of resorcinol and p-aminophenol is what you need if you want to find out if blondes do indeed have more fun.
Unfortunately, repeated dying damages the cuticle, leading to roughness and easy breakage but modern dyes contain conditioners that help maintain the cuticle's integrity. Thickeners can also be added to ensure that the dye does not run down the face and ultraviolet light absorbers keep the newly developed colour from fading in the sunlight.
A further problem with the p-phenylenediamines is sensitization. Some users develop dermatitis on the upper eyelids or the rims of their ears but in rare cases there may be a whole body reaction characterized by reddening and swelling of the skin. Many European manufacturers have replaced p-phenylenediamine by toluene-2,5-diamine sulphate, which is less of a sensitizer.
Although "permanent" dyes are by far and away the most popular, "semi-permanent" and "temporary" dyes are also available. The semi-permanent ones have no ammonia or peroxide and are composed of small coloured molecules that can diffuse into the cortex. They resist several shampooings. Nitro-phenylenediamines are the most versathe temporary dyes, and although they are similar to compounds found in permanent dyes, they are used in smaller concentrations. Furthermore, some researchers believe that the potential carcinogens in permanent dyes are actually created through the oxidation process. 4-Aminobiphenyl, a recognized bladder carcinogen, can form as an undesired contaminant in permanent dyes. Temporary dyes are composed of molecules that are too large to penetrate the cuticle and just stick to the surface of the hair shaft and can be readily washed away. These dyes are less appealing in terms of efficacy, but are less controversial. Aside from the rare possibility of an allergic reaction, they have been shown to be remarkably safe.
The permanent dyes, however, are shrouded in controversy. Some of their component molecules cause cancer in test animals and several human epidemiological studies have raised the spectre of a link to bladder cancer and non-Hodgkin's lymphoma in humans. A highly publicized study at the University of Southern California suggested that women who used permanent dyes regularly over 15 years tripled their risk of bladder cancer. Sounds ominous, but since the risk of bladder cancer is only about one in 14,000, even a tripled risk is very small. A number of other studies have found no link to any cancer at all. Particularly noteworthy is the Nurses Health Study that followed over 90,0O0 nurses and found no evidence for any association between hair dyes and cancer. It should also be noted that hair dyes have undergone a number of changes in recent years and the compounds used now are not the same as the ones that most people used in the studies that suggested a cancer link. Anyone truly concerned, though, can switch to semi-permanent dyes or temporary ones that have not been implicated in the cancer controversy.
Eventually, biotechnology may put an end to this controversy. Wouldn't it be great if a gene that codes for hair colouring could be inserted into hair follicles, the tiny organelles in our scalp from which hair grows. This may not be as outlandish as it sounds!
AntiCancer, a California biotech company, has some intriguing preliminary results along these lines. All right, so they are with mice and not with humans. And the hair is green, and only under blue light. But it's a start. The California researchers were successful in isolating a gene from jellyfish that codes for the production of a protein that glows green in blue light. They then incorporated this gene into an adenovirus and placed a piece of cultured mouse skin into the virus solution. Within hours a green pigment could be seen in the follicles. When the skin was transplanted to live mice, about 80 percent of the hairs that grew were green! This idea may appeal to some of today's teenagers who favour the idea of fluorescent hair. Although there are simpler ways to do this--like with Kool Aid. Inventive teens have discovered that this beverage can do more than quench thirst. They've taken to immersing their hair in a hot solution of the stuff to achieve some amazing effects. Of course one must take care not to end up with a coloured forehead as well. Cherry flavour apparently is the preferred variety. As one somewhat scientifically challenged teen put it, "I don't like to put chemicals in my hair, I just prefer to use Kool Aid." Well, he's probably right about the safety business. Kool Aid is probably more dangerous when drunk than when applied to the hair.
While Kool Aid may be fine for teens who want a punk look, it's hardly suitable for the older set interested in covering up the grey. This is where lead acetate comes into the picture. Dyes that guarantee to banish the grey hairs from your head so gradually that no one will be the wiser actually cover the grey with lead sulfide. It is the brown-black color of this compound that does the trick. The active reagents in these hair products are lead acetate and elemental sulfur. Lead acetate is a water-soluble compound, but lead sulfide is practically insoluble. When exposed to the air and to hair, lead acetate reacts with sulfur to form lead sulfide, which precipitates on the hair. Proteins in hair also break down with time and release sulfur compounds that react with the lead acetate and enhance the effect. Repeated use of such anti-greying products builds up the lead sulfide, gradually returning hair to a youthful color. At least, that's what the ads say. You can usually identify people who have been using the stuff because their hair will have a dark, dull tinge. Still, many think this is better than going grey.
There is, however, one lingering concern about such products. Lead is a highly toxic element capable of poisoning the enzymes that make hemoglobin. As a result, a hemoglobin precursor called aminolevulinic acid accumulates in the body and causes toxic symptoms ranging from stomach problems to brain abnormalities. The amount of lead in these dyes is very small--less than one percent--and studies indicate that our blood absorbs virtually none of it. But does it contaminate the hands of those who apply it? And what about the excess lead acetate that winds up in our water supply?
Yet another problem arises when people use a permanent dye after having coloured their hair with a metallic dye. Many metals, including lead, catalyze the decomposition of hydrogen peroxide into water and oxygen, and this reaction produces a lot of heat. It can actually cause scalp burns.
So there you have a summary of the hair dye saga. Fascinating chemistry, and some interesting toxicological issues. But there is no question that such products make many people feel better and increase their enjoyment of life. More and more, the answer to the question of "does she or doesn't she" is a "yes." "He" is getting in on the action too! And since modern products can be used at home, not even the hairdresser knows for sure. But the "does she or doesn't she" question has taken on a new connotation. In the current environment of worrying about every chemical to which we are exposed, the question in people's minds is "does she or doesn't she increase her risk of cancer?" And that, not even her toxicologist knows for sure.
Popular science writer, Joe Schwarcz, MCIC, is the director of McGill University's Office for Science and Society.
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|Title Annotation:||risks of colouring your hair|
|Comment:||'Do or dye? Do blondes have more fun?|
|Publication:||Canadian Chemical News|
|Date:||Jul 1, 2004|
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