There has long been concern over the chemicals in hair dyes and chemical hair straighteners or relaxers, and whether they are linked to various cancers. Studies have had mixed findings with regard to breast cancer, but a review paper concluded that there is evidence to support a role of hair product use in the risk of early onset breast cancer, especially in African-American women. Other studies found that long term users of dark hair dyes have a significantly increased risk of non-Hodgkin's lymphoma, multiple myeloma, and bladder cancer.
A recent study done in the New York City and New Jersey area looked at both African-American women and white women and their use of various hair chemical products. They found that regularly chemically relaxing hair or dying hair dark brown or black is associated with an elevated risk of breast cancer in both African-American and white women. And women using both types of products had an even higher risk of breast cancer.From Medscape:
African-American and white women who regularly chemically straighten their hair or dye it dark brown or black have an elevated risk of breast cancer, new research suggests. The study of 4,285 African-American and white women was the first to find a significant increase in breast cancer risk among black women who used dark shades of hair dye and white women who used chemical relaxers.
Black women who reported using dark hair dye had a 51 percent increased risk of breast cancer compared to black women who did not, while white women who reported using chemical relaxers had a 74 percent increased risk of breast cancer, the study found. The risk of breast cancer was even higher for white women who regularly dyed their hair dark shades and also used chemical relaxers, and it more than doubled for white dual users compared to white women who used neither dark dye nor chemical straighteners.
The study included adult women from New York and New Jersey, surveyed from 2002 through 2008, who had been diagnosed with breast cancer, plus women of similar age and race but without a history of cancer.....While the vast majority - 88 percent - of blacks had used chemicals to relax their hair, only 5 percent of whites reported using relaxers. For dark hair dye, the numbers flipped, though the differences were not as dramatic. While 58 percent of whites said they regularly dyed their hair dark shades, only 30 percent of blacks did.
The most striking results showed increased risk in the minority of black women who used dark hair dye and white women who used chemical relaxers. Black women who used chemical straighteners and white women who used dark hair dyes were also at higher risk for breast cancer, but that might have been due to chance. James-Todd said that because so many of the black women used chemical relaxers and so many of the white women used dark hair dye, links would have been hard to detect. There’s no reason to believe that chemical relaxers and hair dyes would increase the risk for women of one race and not of another, she said.
Previous studies have shown that long-term users of dark dyes have a four-fold increased risk of fatal non-Hodgkin’s lymphoma and fatal multiple myeloma, the authors write. Prior research also has associated dark hair dye use with an increased risk of bladder cancer. A 2016 report from the U.S. Centers for Disease Control and Prevention found that breast cancer rates are generally similar for black and white women, at around 122 new cases for every 100,000 women per year, although black women with the disease are more likely to die from it. [Original study.]