Research recently published in the International Journal of Cancer suggests that certain hair dyes and chemical relaxants are associated with breast cancer. The research builds on previous investigations that have shown that certain chemicals in hair dye can induce tumors in the mammary glands of rats.
"Hair products contain more than 5,000 chemicals, including some with mutagenic and endocrine‐disrupting properties," write the authors of the new research, which comes from the National Institute of Environmental Health Sciences.
In investigating the links that these chemicals might have with increased risk of breast cancer, the researchers considered data from the Sister Study. The Sister Study includes data from 50,884 women, ages 35-74 years old, all of whom had not personally had breast cancer but who had one or more sisters who had. This large dataset included information regarding hair products used by the women – perfect for exploring any associations to the disease.
Of particular interest to the scientists were the health implications of chemical hair straighteners. The authors note that these hair products "are used predominately by women of African descent," so understanding the effects of certain ingredients may shed some light on the race-related disparity in breast cancer diagnoses and mortalities. Of the 1 in 8 women in the US who is expected to receive a diagnosis of breast cancer at some point in her lifetime, "[B]lack women [are] more likely to be diagnosed with aggressive tumor subtypes and to die after a breast cancer diagnosis," write the authors.
In conducting their analysis, the researchers determined that women who used hair dye regularly in the 12 months leading up to the study were 9% more likely to develop breast cancer. And for women using permanent dyes frequently (every 5–8 weeks) had an increased risk of breast cancer. Interestingly, this risk was different among races: for white women, the risk increased by 8%; for black women, the risk increased by 60%. Semi-permanent or temporary dyes did not show any increased risk.
Chemical hair straighteners were also bad; the researchers saw a 30% increased risk for women who used them every 5–8 weeks or more. The researchers did not see the same differences among races as they observed for hair dyes.
The study authors say that more analysis is necessary in order to draw any causal conclusions. "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," explains study co-author Dale Sandler, Ph.D. "While it is too early to make a firm recommendation, avoiding these chemicals might be one more thing that women can do to reduce their risk of breast cancer."