Ten years ago, before our tumblr account was hacked (and we lost 10 thousand + followers), we featured numerous studies and lead Q&A’s discussing the scientific findings linking the endocrine-disrupting chemicals in commercial hair dye and hair straightening products to a variety of serious health problems, including breast cancer. A significant percentage of our followers at that time were eager for all the information they could get their hands on about the topic. Now, several years (and diagnoses) later, the U.S. National Institute of Environmental Health Sciences (NIEHS) (a subset of the National Institute of Health (NIH) have confirmed what other scientific results demonstrated some time ago: the way these products are currently formulated appear to be downright risky for consumers. More specifically, scientists at the NIEHS/NIH found that women who use permanent hair dye and chemical hair straighteners have a higher risk of developing breast cancer than women who don’t use these products. The study results suggest that breast cancer risk increased with more frequent use of these chemical hair products.
Scientists used data from 46,709 women. The present study evaluated the relationship specifically between breast cancer risk and hair dye and chemical straightener use in a prospective cohort of women ages 35‐74. Hair dye use was reported by more than half of study participants. Nearly three‐quarters of black women reported use of hair straightener in the past year.
In this national prospective cohort study, researchers examined the association between hair dye and chemical relaxer/straightener use and breast cancer risk by ethnicity. Sister Study participants (n = 46,709), women ages 35–74, were enrolled between 2003 and 2009, and had a sister with breast cancer but were breast cancer‐free themselves. Enrollment questionnaires included past 12‐month hair product use.
Straightener use and personal permanent hair dye use were associated with elevated breast cancer risk. Associations for hair dye were strongest among black women. The results revealed that women who regularly used permanent hair dye in the year prior to enrolling in the study were 9% more likely than women who didn’t use hair dye to develop breast cancer. Among African American women, using permanent dyes every five to eight weeks or more was associated with a 60% increased risk of breast cancer as compared with an 8% increased risk for white women.
(On the upside, researchers found little to no increase in breast cancer risk for semi-permanent or temporary dye use.)
Other results revealed that women who used hair straighteners at least every five to eight weeks were about 30% more likely to develop breast cancer. While the association between straightener use and breast cancer was similar in African American and white women, straightener use was much more common among African American women.
Abstract of Statistical Findings
Cox proportional hazards models estimated adjusted hazard ratios (HRs) and 95% confidence intervals (95% CIs) for the association between hair products and breast cancer; effect measure modification by ethnicity was evaluated. During follow‐up (mean = 8.3 years), 2,794 breast cancers were identified. Fifty‐five percent of participants reported using permanent dye at enrollment. Permanent dye use was associated with 45% higher breast cancer risk in black women (HR = 1.45, 95% CI: 1.10–1.90), and 7% higher risk in white women (HR = 1.07, 95% CI: 0.99–1.16; heterogeneity p = 0.04). Among all participants, personal straightener use was associated with breast cancer risk (HR = 1.18, 95% CI 0.99–1.41); with higher risk associated with increased frequency (p for trend = 0.02). Nonprofessional application of semi-permanent dye (HR = 1.28, 95% CI 1.05–1.56) and straighteners (HR = 1.27, 95% CI 0.99–1.62) to others was associated with breast cancer risk.
Many hair products contain endocrine‐disrupting compounds and carcinogens potentially relevant to breast cancer. Products used predominately by black women may contain more hormonally‐active compounds.
The scientists observed a higher breast cancer risk associated with any straightener use and personal use of permanent dye, especially among black women. These results suggest that chemicals in hair products may play a role in breast carcinogenesis.
Journal Reference: Eberle, C. E., et al. Hair dye and chemical straightener use and breast cancer risk in a large US population of black and white women, International Journal of Cancer, December 3, 2019. DOI: https://doi.org/10.1002/ijc.32738 /source