It is not unusual to walk in the street and see people with dyed hair, in particular colours or even more colours together. For example, in artistic high schools, where “creativity reigns”, it is indeed very common to find people with coloured hair. For years many scientists have wondered if this could lead to health problems or not, and the answers have always been inconclusive.

But, a new big study published last Tuesday, has had some sobering results: women who used permanent hair dye or plates or applied plates to others, had a higher risk of developing cancer at breast compared to women who did not use those products.

Hair colouring and breast cancer

The study showed that the link was particularly evident in black women: their use of permanent dye was associated with a 45% higher risk of breast cancer, while white women had a 7% higher risk. The use of the straightener was associated with a risk of breast cancer of 18% higher.

The results suggest that the use of hair dye and hair straightener “could play a role in breast cancer,the study noted. However, women should not be overly alarmed by the results, said lead author Alexandra White, a researcher at the epidemiology branch of the National Institute of Environmental Health Sciences.

“We know that many different factors influence a woman’s risk of developing breast cancer and these risks we see here are significant but they are small,” White said.  “Women should keep it in the context of the rest of their lives, including physical activity and diet. These are all factors we need to consider when we think about our long-term health risks.

Other experts also urged women to remember that correlation does not necessarily mean causality. “Although these findings are intriguing, they do not provide good evidence that hair dyes or chemical hair straighteners are associated with a significant increase in breast cancer risk or that any association of increased risk is causal,” said Paul. Pharoah, professor of cancer epidemiology at the University of Cambridge, in a statement. “Women who have used these products in the past should not worry about their risks.