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Researchers at the National Institute of Environmental Health Sciences found that women who use permanent hair dye and chemical straighteners/relaxers (not to be confused with a hair-straightening tool) have an increased risk of getting breast cancer compared to those who do not use the chemicals.
"In our study, we see a higher breast cancer risk associated with hair dye use, and the effect is stronger in African American women, particularly those who are frequent users,” said corresponding author Alexandra White, Ph.D., head of the NIEHS Environment and Cancer Epidemiology Group.
Aside from skin cancer, breast cancer remains the most common cancer in women in the United States. Every year, roughly 245,000 cases of breast cancer are diagnosed in women and about 2,200 in men, according to the Centers for Disease Control and Prevention.
For years, researchers have been trying to make a connection between hair dye and the disease, but the results have been inconsistent.
Data from nearly 50,000 women who participated in the Sister Study conducted by researchers at the National Institute of Environmental Health Sciences indicated that women who regularly used permanent hair dye within the year prior to the study were 9 percent more likely to develop breast cancer than women who didn’t use the product.
"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."
Researchers also found the link was more evident within African American women, who were associated with having a 45 percent higher risk of developing the disease, according to the findings.
Researchers say African American women who used the permeant hair dye every five to eight weeks or more had a 60 percent higher risk of developing breast cancer, while white women were associated with an 8 percent risk.
Researchers also found women who used chemical straighteners at least every five to eight weeks were about 30 percent more likely to develop breast cancer. Researchers noted that the link between chemical straighteners for both African American and white women were similar.
To date, researchers found little to no increase in breast cancer risk for semi-permanent or temporary dye use.
However, Dale Sandler, Ph.D., chief of the NIEHS Epidemiology Branch, who co-authored the study, noted that although prior evidence supports the study's conclusions, more research needs to be conducted.
Furthermore, while he cautions women to be wary, "it is unlikely that any single factor explains a woman’s risk."