In recent years a number of further studies, which have been picked up on by the media, have suggested that hair dyes could pose a risk for several types of cancer. According to scientists at the University of Santiago de Compostela, this alarming news has been the driving force behind a systematic evaluation of the epidemiogic evidence.
Headed by Bahi Takkhouche, the University team analysed data found in a medical literature search identifying 79 studies from 11 countries to examine the association between use of hair dyes and the relative risk of cancer.
With an estimated one third of women in the US and Europe and 10 per cent of men aged over 40 using some sort of colouring in their hair, the researchers said that the need for a comprehensive study was pressing.
The matter becomes more pressing when considering that some 70 per cent of people dying their hair use permanent dyes - often associated as being the highest risk for the on-set of cancers. The study's authors also point out that the number of people using permanent hair dye products in many parts of Asia is even higher.
The results of a meta-analysis of the scientific evidence looking at the association between cancer and hair dye use has found no strong evidence of increased risk, according to an article published in the May 25 issue of Journal of the American Medical Association.
"Our results indicate that, globally, there is no effect of personal hair dye use on the risk of breast and bladder cancer," the authors reported. "There is a borderline effect for hematopoietic cancers (for example, leukemia and multiple myeloma). However, the evidence of a causal effect is too weak to represent a major public health concern."
In conclusion, the study reports that: "Some aspects related to hematopoietic cancer and other cancers that have shown evidence of increased risk in one or two studies should be investigated further. Efforts should be targeted toward the assessment of the risk of cancer in occupational settings where exposure to hair dyes is more prolonged and has a higher concentration and frequency than personal exposure."
Although the report highlights the fact that the study cannot completely rule out all risks, it does indicate that the average consumer using a hair dye product once or twice a month is not putting themselves at any major risk.
However, those involved in the beauty business, particularly hairdressers who are using such products on a daily business, might well be putting themselves at risk - suggesting that manufacturers might have to consider warning labels for products that are only used in salons.