London, Mar 26 : Covering up those greying hair roots with dyes is injurious to hairdressers and barbers' health, for a new study has found that hair dyes can increase cancer risk.
The risk, warn international experts, could also extend to personal use of the dyes.
The finding is based on two reviews. The first one was based on the evidence provided by the International Agency for Research on Cancer (IARC) in Lyon, France, which found that male hairdressers and barbers were at a "small but consistent risk of bladder cancer".
"A small but consistent risk of bladder cancer was reported in male hairdressers and barbers. Because of few supporting findings by duration or period of exposure, the working group considered these data as limited evidence of carcinogenicity and reaffirmed occupational exposures of haridressers and barbers as 'probably carcinogenic to humans'," the Independent quoted Dr Robert Baan of the IARC and colleagues, as stating The Lancet Oncology.
The second review was conducted on personal use of hair dyes and found that there may be a link between the colours and bladder cancer as well as with lymphoma and leukaemia.
Hair dyes today are classified into three categories - permanent, semi permanent or temporary dyes.
Permanent dyes have colourless "intermediates" and couplers that, in the presence of peroxide, form the dyes by chemical reaction.
Dark hair dyes tend to contain the highest concentration of the colouring ingredients. It was found in the 1970s that some colourants tested positive cancer tests in rats.
They were discontinued the same decade.