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Permanent hair dyes and chemical straighteners have been linked to an increased risk of breast cancer, a new study has found.

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.

Previously, studies into potential links between hair chemicals and cancer have been inconclusive. TNS

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.

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. TNS 

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.”

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.

The Independent