New research from Spain suggests that hair dye does not increase the risk of developing cancer.
Previous epidemiological studies had suggested that hair dye might be a risk factor for several different types of cancer, including bladder cancer. Researchers had speculated that compounds called aromatic amines, which are contained in the dyes, might be responsible for this association.
For the current study, researchers analyzed data from 79 studies performed in 11 countries. The results indicate no increased risk of breast or bladder cancer in people who used hair dye.
Researchers did find small increases in the risks of brain and ovarian cancer, but these results are suspect because they are based on only two studies in each case. Therefore, "they are not as reliable as the results of the rest of the cancers we studied," explains study author Dr. Bahi Takkouche, a preventive medicine professor at the University of Santiago de Compostela in Spain.
The study also showed a small increase in the risk for blood cancers, but the association was weak. "The borderline increase in the risk for hematopoietic cancers. ..may be easily explained by publication bias," Takkouche says. "Publication bias exists when there are studies that are not published, either because the editors reject them or because the authors themselves fail to send them for publication. These studies are generally negative."
The data should give reassurance to people that the risks of modern hair dye usage as a predisposition to cancer ate, at most, very minimal," says Dr. Robert Morgan Jr., section head of medical gynecologic oncology at City of Hope Cancer Center in Duarte, California.
"Our study is just the best summary of current scientific knowledge on the topic," says Takkouche. However, he suggests the results be interpreted cautiously. "One can never rule out that, in the future, several individual studies will find strong harmful effects. Still, the news is quite reassuring for hair dye users," he says.
The study authors say more research may be needed on a possible link between hair dyes and such cancers as leukemia and multiple myeloma, as well as occupational exposure to hair dyes, such as that encountered by hair stylists and cosmetologists. Here, the exposure is higher and more prolonged than with personal use, Takkouche notes.
According to information from the authors of the current study, approximately one-third of women in Europe and North America color their hair, as do approximately 10% of men over the age of 40. The majority (approximately 70%) use permanent dyes.