Regular use of permanent hair dye, as well as chemical straighteners, could increase the risk of breast cancer in women, according to a new study published by the International Journal of Cancer.
Researchers observed a total of 46,709 American women aged from 35 to 74 and found that there is a close relationship between permanent hair dye and breast cancer.
The connection stems from “endocrine‐disrupting compounds and carcinogens potentially relevant to breast cancer” included in many hair products. Straighteners also contain carcinogens such as formaldehyde.
A group of women among those regularly dying their hair seemed to increase their risk of developing breast cancer by nine percent.
Evaluating their findings by ethnicity, the research team discovered that black women who heavily used hair dye are 60 percent more likely (45 percent for regular users) to develop the disease than women who didn’t use it.
For white women, the figure was seven percent for regular users and eight percent for heavy users.
“Products used predominately by black women may contain more hormonally‐active compounds,” the research says.
“Heavy use” is described as every five to eight weeks or more.
The International Journal of Cancer published the research on December 3, 2019. The results are actually part of a more comprehensive study titled the “Sister Study” conducted by the US National Institute of Environmental Health Sciences (NIEHS).
As part of the Sister Study, over 50,000 women in the US and Puerto Rico between the ages of 35 and 74, who all had at least one sister diagnosed with breast cancer. It has been investigating factors that possibly cause breast cancer in women.