A lot of women use permanent hair dyes and chemical hair straighteners. A new study shows using them could increase their risk of breast cancer.

Researchers at the National Institute of Environmental Health Sciences (NIEHS) used data from 46,709 women. They found women who regularly used permanent hair dye in the year prior to enrolling in the study were 9 percent more likely than women who didn't use hair dye to develop breast cancer. The research team found little to no increase in breast cancer risk for semi-permanent or temporary dye use.

Among African American women, using permanent dyes every five to eight weeks or more was associated with a 60 percent increased risk of breast cancer as compared with an 8 percent increased risk for white women.

"Researchers have been studying the possible link between hair dye and cancer for a long time, but results have been inconsistent," said corresponding author Alexandra White, Ph.D., head of the NIEHS Environment and Cancer Epidemiology Group. "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."

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Researchers found women who used hair straighteners at least every five to eight weeks were about 30% more likely to develop breast cancer.

10News talked with a doctor at Moffitt Cancer Center about the study.

“There are a lot of chemicals in hair dyes and hair straighteners. In fact, some have more than 5,000 chemicals in them. it turns out some of those chemicals can act like estrogen, sex hormones in women, that we know can increase risk of breast cancer,” says Dr. Shelley Tworoger.

The co-author, Dale Sandler, Ph.D., chief of the NIEHS Epidemiology Branch, says although there is prior evidence to support the association with chemical straighteners, more studies need to take place.

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When he was asked if women should stop dyeing or straightening their hair, Sandler said "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. 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."

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