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Woman getting her hair dyed

Will Using Hair Dye Increase the Risk of Breast Cancer?

In a movement that has trended on social media, women all over the world are #DitchingTheDye to embrace their natural hair color, save money and accept the changes that come with aging. Some women may also start ditching the dye as a result of findings published in December, 2019, linking use of hair dyes and chemical hair straighteners to increased breast cancer risk.

The results are from the Sister Study, a research study conducted by the National Institutes of Health (NIH) over eight years and involving more than 46,000 women. Investigators concluded that overall, women who used permanent hair dye regularly (every five to eight weeks) were 9% more likely to develop breast cancer than women who didn’t use permanent hair dye. But the biggest surprise was the difference between African-American/black women and white women. While white women saw an 8% increased risk, routine coloring with permanent dye was associated with a 60% higher risk for breast cancer among black women.

Additionally, dye color appeared to impact black and white women differently. Darker dye shades were associated with a 51% increased breast cancer risk for black women and an 8% increased breast cancer risk for white women. Lighter shades increased the risk by 46% for black women and 12% for white women. The research team found little to no increase in breast cancer risk for semi-permanent or temporary dye use. Frequent use of chemical straighteners was also associated with an 31% increased risk of breast cancer overall, with similar but weaker relationships when looking separately in white and black women.

Roswell Park’s Christine Ambrosone, PhD, Chair of the Department of Cancer Prevention and Control, helps explain what the data means for women who color or straighten their hair. Dr. Ambrosone’s own research focuses on genetic and non-genetic causes of cancer and cancer survival, particularly in breast cancer.

“This was a good, legitimate study,” says Dr. Ambrosone. “It included a large sample size and it was done by a reputable team of researchers, with statistically reliable results. However, it’s important to note that this was what is known as an observational study. In this case, the data were self-reported by the participants, which can result in some inaccuracies and biases.

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In addition, although the study did account for some other factors that may affect a woman’s cancer risk, such as smoking and unhealthy weight, other factors associated with use of hair dye could be driving the relationships. Furthermore, although this was a large cohort of women, the numbers became fairly small when limiting to those who used hair products and developed breast cancer, particularly when looking separately for black and white women.

“While the findings definitely show us a trend,” says Dr. Ambrosone, “highly controlled experimental research would be necessary to confirm an indisputable link between the use of permanent hair dye and hair straighteners and breast cancer, and to determine what causes that link.”

Why the Higher Risk for Black Women?

“The easy answer is that straighteners and darker dyes are more likely to affect black women because these products are used by black women more than they are by white women. In this study, about 75% of black women reported that they straightened their hair.

"Additionally, it is thought that hair care products made specifically for black women have higher levels of endocrine-disrupting chemicals. From previous research, we know that some compounds may bind to estrogen receptors, stimulating estrogen production, which in turn, can promote the growth of breast tumors.”

Should I Avoid Certain Products?

“This study did not look at the specific ingredients in the products women were using, only whether they had used various hair dye colors and products and whether they later developed breast cancer. It is estimated that hair products contain more than 5,000 chemicals — some of which may have mutagenic (gene mutating) and endocrine-disrupting properties which can raise cancer risk.

"One hair care ingredient we do know is carcinogenic is formaldehyde, which is found in a hair straightening treatment known as a 'Brazilian blowout.'”

Should I Stop Dying or Straightening My Hair?

“Well, I might suggest some modifications. For instance, if women really want to dye or straighten their hair, I might advise lighter shades and dying less frequently to lower their risk. Or, use temporary hair dyes — which were not linked to increased breast cancer risk — instead of, or more frequently than, permanent dyes.

"But my most important takeaway from this study is this: statistically, compared to many other carcinogens and risk factors, the overall risk of breast cancer from using permanent hair dyes and straighteners is quite low.

"You can take other, proven actions to decrease your breast cancer risk. These include avoiding or reducing alcohol consumption, maintaining a healthy weight, increasing physical activity and limiting or avoiding hormone replacement therapy.”