New research suggests women who use permanent hair dyes and chemical hair straighteners may face an increased risk of developing breast cancer.
The findings were published this week in the International Journal of Cancer (IJC), indicating that common hair dyes and straighteners often contain known carcinogens and other hormone disrupting compounds.
Researchers from National Institute of Environmental Health Sciences (NIEHS) collected data from the Sister Study, which is a long-term research project in the U.S. and Puerto Rico involving over 50,000 participants to study how the environment and genes affect women’s chances of getting breast cancer.
Part of the study involved participants answering questionnaires about hair products they used in the past year. More than half of the women reported using permanent hair dyes, and 75% of African-American participants reported using chemical straighteners.
Over an eight year period, researchers identified 2,794 cases of breast cancer from participants reporting having used or frequently using permanent hair dyes and chemical straighteners.
The data indicates women who reported regularly using permanent hair dyes in the year prior to enrolling in the study were 9% more likely than those who didn’t to develop breast cancer. Researchers pinpointed that African American women who reported using permanent hair dyes regularly were associated with a 60% increase of breast cancer diagnosis, compared to an 8% increased risk for Caucasian women.
Similarly, researchers discovered an association between the use of chemical hair straightener and breast cancer diagnosis. NIEHS scientists reported that women who used hair straighteners frequently, at least every five to eight weeks, had a 30% increased risk of developing breast cancer.
The findings are similar to a study published in 2017, which found that African American women who use dark hair dyes and Caucasian women who use relaxers and straighteners both face increased cancer risks.
Although researchers indicated there are many factors that play a role into the risks of developing breast cancer, hair products are known to contain on average more than 5,000 chemicals, including some that may damage DNA or interfere with the body’s endocrine system. Exposure to this wide array of chemicals could allow them to enter an individual’s blood stream and circulate through the body.
Previous studies have indicated many hair product designed for African-American women contain higher concentrations of estrogens and more hormone disrupting chemicals, such as formaldehyde, which is a known carcinogen.
Co-author of the study Dale Sandler, Ph.D., chief of the NIEHS Epidemiology Branch, cautioned that although there is supporting evidence to the study, additional research is required to replicate the data. Sandler stated that although the association has not been confirmed, women should attempt to avoid hair dye and straightener chemicals as best they can.
The American Cancer Society recommends women always take precautions when using hair dyes or straighteners and to always wear gloves when applying hair dye, never leave the dye on your head any longer than the directions say you should and always rinse your scalp thoroughly with water after use.