Women who regularly use permanent hair dye may be putting themselves at increased risk of bladder cancer, new research findings suggest.
The study is the first to show that how often you use hair dyes affects your bladder cancer risk.
Researcher Dr Manuela Gago-Dominguez has conducted a series of studies on bladder patients and healthy women – all of the same age – and found a link between bladder cancer and hair dye.
In the latest research Dr Gago-Dominguez, of the University of Southern California School of Medicine in Los Angeles, and her colleagues analysed 897 cases of bladder cancer where information about hair dye use was available.
They compared these patients with a similar number of adults who did not use permanent hair dye.
The investigators found that women who used permanent hair dye at least once a month were twice as likely to develop bladder cancer, as women who did not use permanent hair dye.
They took cigarette smoking – a known risk factor for bladder cancer – into consideration in their calculations.
The study findings will be published in the February issue of the International Journal of Cancer.
Dr Manuela Gago-Dominguez said: ‘Our novel observations are provocative and carry enormous public health implications.
‘Yet it is a little premature to make any recommendation about stopping the use of permanent hair dyes.’
‘However, this is one of the largest and most comprehensive studies ever conducted on the issue and we think our results should not be ignored.’
Those who reported regular use of the hair dye for at least 15 years were more than three times as likely to develop bladder cancer as non-dye users, concluded the study.
Even some hairstylists and barbers were 50 per cent more likely to have bladder cancer than those who did not experience occupational exposure.
But according to Dr John Corbett, a consultant to the Cosmetic, Toiletry and Fragrance Association, Dr Gago-Dominguez and her team may have used a faulty study design.
‘Their measure of exposure is just frequency of use and duration of use, which is not very good,’ said Dr Corbett.
He added: ‘The most important factor in exposure to hair dye is the shade you use.
‘All of the shades use essentially the same chemicals, but there’s quite a lot more of them (the chemicals) in dark brown and black than there are in blonde.’
Also, Corbett contends that the researchers ‘seem to make light of previous studies’ by the National Cancer Institute and the American Cancer Society that failed to find a similar association between hair dye use and cancer risk.
He said: ‘The bottom line is I don’t think (the new study findings) should affect people in their decision as to whether to use hair colour or affect the hair colour industry in considering that they sell safe products.’