If you're a woman, regular dyeing or straightening of your hair may be a hidden risk. The study found an association between the use of permanent hair dyes and smoothing agents and an increased risk of breast cancer in women, especially in black women.
Researchers from the National Institutes of Health studied data from a previous government project to investigate the long-term health of healthy women in the US whose sisters had cancer before, and aptly named this sister study. The project interviewed women about the use of hair care products over a 12-month period prior to their inclusion in the study. Based on these data, they recorded the health status of approximately 45,000 US women between the ages of 35 and 74 over an average of eight years.
Women who regularly used hair dye before starting the study said that this was 9 percent more likely than women who did not use hair dye to develop breast cancer. And those using hair straighteners were 1
The study results were published on Tuesday in the International Journal of Cancer.
As is common in the study of cancer risk, such studies can only indirectly indicate that something is causing cancer. While some studies point to an association between hair dyes and cancer, the evidence is mixed in total . However, a review from 2018 that focused specifically on breast cancer showed a positive association with hair dyes.
Biologically, it is certainly possible that hair dyes could be used cause cancer. It is estimated that these products contain about 5,000 different chemicals, some of which are carcinogenic in themselves. Our cancer risk can also be influenced by many different factors that reinforce each other, including our ethnicity.
For example, in the new study, the team found that black women had a much higher risk – 60 percent – of using hair dye every five to eight weeks, compared to black women who did not. Both white and black women had a similar increased risk when it came to hair straighteners, but black women tend to use these products more often, the authors noted.
Of course, cancer is a complicated disease and few things that can cause cancer increases our risk many times over. For example, about half of the 46,000 women participating in the study stated that they regularly use hair dye. Overall, 2,764 women (around 17 percent) contracted cancer for the duration of the study. A relative increase in risk of 9 percent in women who have consumed hair dyes therefore means a very small increase in the absolute risk.
In view of the mixed evidence so far, further research is needed in the opinion of the authors to confirm this link. However, it makes perfect sense to avoid the use of hair dye and smoothing agents if you are really worried. And there could be ways to reduce your already low potential risk. The researchers find that women whose hair has been professionally dyed and smoothed may be at a lower risk than women who do so themselves ( previous research found that hairdressers are at increased risk of cancer ) and darker hair dyes are likely to surprise users in more of these in terms of chemicals.
"We are exposed to many things that may possibly contribute to breast cancer and it is unlikely that a single factor will explain a woman's risk. Although it is too early to make a clear recommendation, avoiding these chemicals could be another way for women to reduce the risk of breast cancer, "said study author Dale Sandler, chief epidemiologist at the National Institute of Environmental Health Sciences, NIH Statement of the NIH.