There has been widespread concern recently that chemicals in hair dye used by a growing number of men ad women - could cause bladder cancer, among other things. So how worried should we be?
Spanish researchers, analysed 79 studies from 11 countries. Their conclusions?
"Our results indicate that, globally, there is no effect of personal hair dye use on the risk of breast and bladder cancer," they report. The researchers say they found a borderline link with blood and bone marrow cancers, but not enough of risk-factors for any major health concern.
The area that still needs looking into is whether there is a risk to people using dye in occupational settings, since they are exposed to more chemicals.