Hair dye, chemical straightener use associated with increased breast cancer risk according to new study
The study found that women who use permanent dye or straighteners are at a higher risk of developing breast cancer than women who do not use these products.
1 in 8 U.S. women will develop breast cancer over the course of their lifetime (1). In 2019 alone, over 268,000 new cases of invasive breast cancer are expected to be diagnosed. A new study, run by researchers at the National Institute of Environmental Health Sciences (NIEHS), took aim at better understanding the different reasons women get breast cancer so that recommendations can be made for prevention in the future.
The study followed 46,709 women ages 35-74 from 2003 to 2009. Participants were eligible if they had no history of breast cancer but had at least one sister with a diagnosis. Throughout the duration of the study, there were 2,794 breast cancer cases reported.
The study found that women who use permanent dye or straighteners are at a higher risk of developing breast cancer than women who do not use these products. Specifically, women who regularly used permanent hair dye in the year prior to enrolling in the study were found to be at a 9% higher risk for breast cancer. The risk is also considerably higher for black women – who were observed to be at a 45% higher risk compared to 7% in white women. Though not entirely conclusive, the increased risk for black women is consistent with toxicological assessments that report higher concentrations of endocrine-disrupting compounds and estrogens in hair products marketed to black women (2). Among white women, the increased risk of breast cancer was associated with light-colored dye but not dark dye.
The study also observed that there was little to no risk associated with semi-permanent or temporary dye use; however, an increased risk was observed for non-professional or at-home applications. This could be attributed to potential absorption on hands or forearms when the dye is applied or inhalation of toxic chemicals in poorly ventilated areas. So if you are someone who uses at-home dye kits or applications, make sure to follow the product’s safety instructions carefully if you do choose to continue applying dye at home.
Regarding straightener use, the study found that women who used straighteners in the year before enrollment were at an 18% higher breast cancer risk, and this risk was directly correlated with frequency of use. Unlike hair dye use, though, this risk did not notably vary by ethnicity.
What to do about it
Products like hair dye and hair straightener are very common and widely used – it is estimated that more than one third of women over age 18 in the U.S. use hair dye (3). Hair products also contain more than 5,000 chemicals, which according to this study, may play a role in breast carcinogenesis.
As we interpret these findings, though, it is important to note that the study analyzed association and not causation. “Researchers have been studying the possible link between hair dye and cancer for a long time, but results have been inconsistent,” says Alexandra White, Ph.D., who serves as head of the NIEHS Environment and Cancer Epidemiology Group. When asked if women should stop dyeing or straightening their hair, Dale Sandler, Ph.D., chief of the NIEHS Epidemiology Branch responds, “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 (4).”
There are cancer risks, though, that women can control. Dr. Otis Brawley, a professor at the Johns Hopkins University Bloomberg School of Public Health and former chief medical officer at the American Cancer Society, adds, “tobacco use, obesity, an excess of calories and a lack of exercise are the leading preventable risk factors for cancer that people can change. They’re linked to at least 12 cancers,including breast and endometrial cancers. Alcohol consumption, too, is more clearly linked to the risk of breast cancer than chemical dyes and straighteners.”