The findings, published in the International Journal of Cancer, come after years of concerns regarding the potential impacts hair products have on health.
Previously, studies into potential links between hair chemicals and cancer have been inconclusive.
However, according to scientists at the National Institutes of Health (NIH) and the National Institute of Environmental Health Sciences, women who used permanent hair dye or straighteners, or applied straighteners to others, had a higher risk of developing breast cancer than women who weren’t exposed to the products.
Researchers also found that the risk was greater for black women who used the products.
To study the health risks associated with hair products, researchers analysed data from 46,709 women ranging in age from 35 to 74 and enrolled in the Sister Study, which recruited women whose sisters had been diagnosed with breast cancer.
After analysing answers to questions regarding the women's health, lifestyle and demographics, the researchers found that women who regularly used permanent hair dye in the year prior to enrolling in the study were nine per cent more likely to develop breast cancer than women who didn’t.
Among black women, using permanent hair dye was associated with a 45 per cent higher risk of developing breast cancer.
When the permanent hair dye was used “every five to eight weeks or more” the risk rose to 60 per cent in black women, according to the researchers.
“Researchers have been studying the possible link between hair dye and cancer for a long time, but results have been inconsistent," said corresponding author Alexandra White, PhD, head of the NIEHS Environment and Cancer Epidemiology Group. "In our study, we see a higher breast cancer risk associated with hair dye use, and the effect is stronger in African American women, particularly those who are frequent users."
The risk was not found to be associated with semi-permanent or temporary hair dye.
For women who used chemical hair straighteners, the risk of developing breast cancer increased by 18 percent, but researchers acknowledged that the results needed to be replicated in other studies.
As for whether women should stop dyeing or straightening their hair, co-author Dale Sandler, PhD, chief of the NIEHS Epidemiology branch, said: “We are exposed to many things that could potentially contribute to breast cancer, and it is unlikely that any single factor explains a woman’s risk.
“While it is too early to make a firm recommendation, avoiding these chemicals might be one more thing women can do to reduce their risk of breast cancer.”
However, experts aren’t necessarily convinced that women need to avoid permanent hair dyes or chemical straighteners.
Following the publication of the study, Paul Pharoah, professor of cancer epidemiology at the University of Cambridge, said: “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.
“Women who have used such products in the past should not be concerned about their risks.”
Although the causes of breast cancer are not fully known, the NHS states that factors such as family history, age, breast density, and lifestyle factors such as weight and alcohol consumption may all contribute to the risk of developing the disease.