Study: Hair dyes, straighteners may increase breast cancer risk for black women

Black women who use permanent hair dyes and chemical hair straighteners are at a higher risk of developing breast cancer than those who don’t use these products, a new study has shown.

The study, titled “Hair dye and chemical straightener use and breast cancer risk in a large US population of black and white women,” examined the relationship between hair dye and chemical relaxer/straightener use and breast cancer risk by ethnicity.

The research was conducted in the US using 46,709 black and white women — between the ages of 35 and 74 — recruited between 2003 and 2009, who had no personal history of breast cancer, but had a sister diagnosed with the disease.

Findings from the study, published in the International Journal of Cancer, showed “a higher breast cancer risk associated with any straightener use and personal use of permanent dye, especially among black women” which suggests “that the chemicals in hair products may play a role in breast carcinogenesis.”

The researchers also stated that “many hair products contain endocrine-disrupting compounds and carcinogens potentially relevant to breast cancer,” adding that “products used predominately by black women may contain more hormonally-active compounds.”

“We evaluated the relationship between hair dye and straightener use with breast cancer risk and found that women who used permanent dye or straighteners, or applied straighteners to others, in the 12 months before enrollment were at a higher breast cancer risk,” said the study.

The link was particularly evident in black women as their use of permanent dye was associated with 45 per cent higher breast cancer risk, while white women faced a seven per cent higher risk.

“The association with permanent hair dye was particularly evident in black women, for whom we observed a 45% higher breast cancer risk. Overall, these results support the hypothesis that hair dye and straightener use, which are highly prevalent exposures, could play a role in breast carcinogenesis,” it added.

“The study also implicated hair straighteners, finding a 30 percent increase in the risk of breast cancer among women of all races who reported regular use of the products. African-American women were much more likely than white women to use hair straighteners.

“In conclusion, these findings from a large, prospective cohort with a sufficient sample size to separately evaluate results for white and black women provide evidence to support the relationship of hair dye and straightener use with breast cancer risk and highlight potential differences in associations by ethnicity.”

Alexandra White, head of the National Institute of Environmental Health Sciences Environment and Cancer Epidemiology Group, also took to her social media page to summarise the findings of the study.

“The risk associated with permanent dye was small for white women (<10%) but for Black women was much higher (45%) suggesting the type or amount of dye used or application method varies substantially and influences risk,” she wrote on Twitter.

The risk associated with permanent dye was small for white women (<10%) but for Black women was much higher (45%) suggesting the type or amount of dye used or application method varies substantially and influences risk

— Alexandra White (@alexandrajwhite) December 4, 2019

White, a senior author of the study, however, told women not to be overly alarmed by the findings.

“We know that a lot of different factors influence a woman’s risk of developing breast cancer, and these risks we see here, they are meaningful but they are small,” she said.

“Women should take that into context with everything else in their life, including their physical activity and diet.

“These are all factors we have to consider when we’re thinking about our long-term health risks.”

Paul Pharoah, a professor of cancer epidemiology at the University of Cambridge, also urged women to remember that correlation does not mean causation.

“While these results are intriguing, they do not provide good evidence that hair dyes or chemical straighteners are associated with a meaningful increase in risk of breast cancer or that any increased risk association is causal,” said Pharoah.

“Women who have used such products in the past should not be concerned about their risks.”