Hairdressers may face an increased risk of cancer because of the dyes and other chemicals they work with, according to the World Health Organisation's International Agency for Research on Cancer (IARC).
"Occupation as a hairdresser or barber entails exposures that are probably carcinogenic," says a report compiled by a working group for the agency, which is based in Lyon, southern France.
The study is a review of half a dozen large investigations into cancer risk.
Among male hairdressers and barbers, the risk of cancer of the bladder was between 20 and 60 percent higher compared with the general population.
The risk is described as "small but consistent" and is less visible among women.
Among both men and women, some studies pointed to a heightened risk of 30 percent for lung cancer, although this could be partly explained by higher incidence of smoking among hairdressers.
Among women alone, some studies pointed to an increased risk for ovarian cancer and of non-Hodgkin's lymphoma, but this was contracted by others.
The journal The Lancet Oncology reports on it on Wednesday in its latest issue.