Women who regularly use permanent hair dye could have up to 60 percent risk of breast cancer, according to scientists writing in the International Journal of Cancer.
A study based on medical records of more than 45,000 women found a positive correlation between permanent hair dye and breast cancer — particularly among black women.
The paper is based on patterns and trends, and doesn’t confirm a direct cause. However, it adds to research suggesting there may be carcinogens lurking in commonly-used beauty products.
“The results do not surprise me,” Otis W. Brawley, medical oncologist and epidemiologist at the Hopkins-Kimmel Cancer Center, told Newsweek.
“Many of us have worried that the chemicals in especially the permanent hair dyes and hair straighteners have the potential to cause cancer.”
Taken as a group, women who regularly dyed their hair appeared to be increasing their risk of developing breast cancer by 9 percent. For black women, the risk of developing the disease was significantly higher at 45 percent.
This increased even further, to 60 percent, among black women who heavily used hair dye. The study defined the heavy use as once (or more) every five to eight weeks.
In contrast, the associated risk for white women was 7 percent for regular use and 8 percent for heavy use.
There also appeared to be differences depending on the type of hair dye used. Dark hair dye was associated with a 51 percent increase in risk for black women and an 8 percent in risk for white women. In case of light hair dye, there appeared to be a 46 percent increase in risk for black women and a 12 percent increase risk for white women.
It is unclear as to why there are racial variations. But the researchers suggest it may be linked to differences in the way it is used or differences in the way products are made for black and white audiences.
They also found a significant correlation between breast cancer risk and chemical hair straighteners, with the researchers emphasizing this needs to be backed up by other research.
However, the study found the risk to be consistent, increasing across all races by 30 percent for women who use chemical hair straighteners every five to eight weeks or more.