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Hair dyeing without any risk - is that possible?

27/2009, 28.10.2009

BfR Symposium on the latest scientific findings about cancer and allergy risks from hair dyes

Hair dyes have attracted major attention since the evaluation of epidemiological studies from the USA from 2001 identified signs of an elevated risk of bladder cancer amongst hairdressers and consumers who had used hair dyes particularly prior to 1985. This prompted the European Commission to launch a systematic safety assessment of all substances used in hair dyes with a view to drawing up a positive list of safe substances. Some of the main commercial substances used in hair dyes are also sensitising and can, therefore, trigger allergic skin reactions. At the Federal Institute for Risk Assessment (BfR) in Berlin around 100 representatives from science, public authorities, industry, consumer associations and the media came together in order to present the latest scientific findings available on the risk of cancer and sensitisation, and to discuss the need for further research. "There is no risk of cancer through hair dyes for consumers", says BfR President Professor Dr. Dr. Andreas Hensel. The problematic substances had been banned for years. "There is, however, a need for research on the problem of allergies caused by hair dyes."

Around one-third of women in Europe and North America dye their hair as do about 10% of men over the age of 40. Henna, the oldest hair dye from the leaves and young shoots of the Henna shrub, was already used in the 14th century B.C. by women in Egypt. The first commercial dye - para-phenylene diamine (PPD) - was placed on the market in 1907. PPD has highly sensitising properties and can trigger contact allergies. PPD is used as a precursor to the colour shade. The actual colour develops in a chemical reaction with the oxidation coupler in the hair. In hair clinics in Europe between three and five percent of the patients with contact allergies are sensitive to PPD. However, it is estimated that only around one-third of these cases can be attributed to the use of hair dyes. Dyes in textiles and leather, and henna tattoos could be the cause of the other cases. Clinical-dermatological allergy tests as well as the self-tests recommended by some hair dye manufacturers are under discussion as possible contributory factors to sensitisation. The use of PPD in hair dyes in Germany is on the decrease; however, some of the alternatives are problematic.

Following the worrying epidemiological observations of a possible association between the occurrence of bladder cancer and the use of hair dyes in the USA, the EU launched a broadly based programme that firstly promotes epidemiological studies in Europe. Secondly, industry was called on to undertake basic research in order to elucidate the chemical processes in oxidative hair dyes with a view to establishing the consequences for safety assessment. In order to be able to draw up a positive list of safe substances for hair dyes, industry had to prepare scientifically robust dossiers for the safety assessment of these dyes. They are evaluated by an independent scientific committee. The number of substances used in this method was significantly reduced, too.

The evaluation of the available epidemiological findings about a possible association between cases of cancer and hair dye use does not produce a uniform picture. Most experts are of the opinion that there are not enough data to establish a clear, statistical association. For consumers there is no health risk from hair dyes because the problematic substances have been banned for a long time.

At the BfR Symposium on the subject of hair dyes, further, recent research findings were presented particularly concerning differences in metabolism in conjunction with the intake of substances through the skin compared with dietary intake. Discussions also focussed on new methodological, non-animal approaches that permit statements on the toxicity of chemical substances. The problem of sensitisation leading to allergic reactions caused by hair dyes, particularly in hairdressers, has still to be resolved and requires further basic research.

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