Hair dye, chemical straighteners linked with breast cancer in large study

December 19, 2019

Carolyn Eberle

Women who routinely use permanent hair dye may have a higher risk of breast cancer, according to research conducted by a team including Carolyn Eberle, a doctoral student of epidemiology at the UNC-Chapel Hill Gillings School of Global Public Health.

A recent study based on the large Sister Study cohort of more than 46,000 women found a connection between permanent hair dye and breast cancer — particularly among African-American women.

Overall, study participants who regularly dyed their hair with permanent dye had a 9% greater risk of developing breast cancer. For African-American women, the risk was 45% higher. (The risk increased even further, to 60%, among African-American women who used permanent hair dye very frequently — defined as at least every five to eight weeks.)

The researchers found little to no increase in breast cancer risk with the use of semi-permanent or temporary dye.

Dr. Alexandra White

First author Eberle worked with senior author Alexandra White, PhD — an alumna of the Gillings School’s epidemiology department who is now the head of the Environment and Cancer Epidemiology Group at the National Institute of Environmental Health Sciences (NIEHS)— and with NIEHS scientists Dale Sandler, PhD, and Kyla Taylor, PhD, to conduct the research. Their report was published online December 4 by the International Journal of Cancer.

The Sister Study, a national cohort study of 50,884 women ages 35 to 74 years old, enrolled women from 2003 to 2009. All Sister Study participants had a sister with breast cancer but were free of breast cancer themselves. (The co-authors point this out as a consideration: “By design, all study participants have a family history of breast cancer, which may limit the generalizability of these findings. However, this would not affect the internal validity of the study.”)

The researchers also found an association between the use of chemical hair straighteners and breast cancer, with women who used straighteners at least every five to eight weeks being about 30% more likely to receive a breast cancer diagnosis. While the link between straightener use and breast cancer was similar in African-American and white women, straightener use was much more common among African-Americans.

Eberle says, “While any association observed in an epidemiologic study must be interpreted with caution, our findings suggest more studies are needed to confirm [these connections] and to evaluate the constituents of hair dyes and straighteners and their potential role in breast carcinogenesis.”

Contact the Gillings School of Global Public Health communications team at sphcomm@unc.edu.