What We Know About the Link Between Hair Dye and Cancer

Q. I color my hair regularly, but I’ve heard that permanent hair dye can increase the risk of cancer. Should I be worried?

Scientists have been looking into the association between hair dye and cancer for decades. And while some research suggests a link, the findings are mixed, making it hard to offer foolproof recommendations, said Alexandra White, an epidemiologist at the National Institute of Environmental Health Sciences.

Still, a closer look at the research could help you make an informed decision about what’s best for you and your hair style.

What Studies Suggest

Much of the research on hair dye has focused on its possible connection to bladder cancer — particularly among hairdressers exposed at work to permanent dyes made before the 1980s, said Dr. David J. Goldberg, a researcher and dermatologist in New York City. The longer the hairdressers worked and were exposed via their skin or lungs, the more likely they were to develop bladder cancer.

But other studies have not found this increased risk, which could be because manufacturers began producing less toxic formulations after the 1970s.

Breast cancer does seem to be associated with permanent hair dye, though, Dr. White said. In a 2019 study involving more than 46,000 women, Dr. White and her colleagues found that those who used permanent hair dye frequently (every five to eight weeks) had a 9 percent higher risk of breast cancer than those who didn’t use hair dye.

That may sound like a big jump, but it’s actually “a really small increase in breast cancer risk” when contextualized with a woman’s lifetime risk, Dr. White said. On average, women have about a 13 percent chance of developing breast cancer, so a 9 percent increase of that value raises her lifetime risk only one percentage point to about 14 percent.

When broken down by race, however, the risk for Black women was significantly higher, Dr. White said. Black women who colored their hair frequently with permanent dye had a 60 percent increase in breast cancer risk, raising their lifetime risk to nearly 21 percent — compared with about 14 percent for white women.

This link between permanent hair dye and breast cancer risk in Black women has been shown in other studies, too. Though it’s unclear what may be driving these racial and ethnic differences, said Dr. Nada Elbuluk, an associate professor of dermatology at the Keck School of Medicine of U.S.C.

One possibility is that other hair products popular among Black women, like chemical hair straighteners, relaxers and leave-in oils, may also play a role. But more research is needed.

Different Types of Dye

According to Dr. Goldberg, study findings may be mixed because the chemical combinations used in hair dyes can vary considerably between products, and they’ve evolved over the years. This makes it impossible to generalize about all hair dyes.

Unlike pharmaceuticals, Dr. White said, hair products are not strictly regulated. Manufacturers don’t need to prove that their products are safe before sale, and because their formulations are often proprietary, it can be difficult to know what’s in them.

However one finding has been fairly consistent. Temporary and semi-permanent hair dyes, which wash out over time, seem to be safer than permanent dyes, which cause lasting chemical changes in the hair shaft.

It’s challenging to know which specific chemicals could be driving the increases in cancer risk, Dr. White said. But research suggests that aromatic amines and phenols, found in permanent hair dyes, have carcinogenic effects.

Safer Strategies

Since no studies have proven that hair dye itself causes cancer, Dr. Elbuluk said, it’s up to you to decide if you want to continue your coloring routine, given any other potential risk factors you may have.

If you want to play it safe, consider these strategies:

Color your hair less frequently. Though it’s not definitive that the more you color your hair, the greater your breast cancer risk, “a good precautionary principle is to lower your frequency of use,” Dr. White said.

Avoid permanent hair dye during pregnancy. It’s not certain that carcinogenic chemicals in hair dye may increase a developing fetus’s risk for cancer long term, but there is evidence that the chemicals may increase the chances of developmental problems. So it’s best for pregnant women to avoid using hair dye “at least for the first trimester,” Dr. Goldberg said.

Follow coloring instructions carefully. When dying at home, wear protective gloves, apply the dye in a well-ventilated room, don’t leave it on your head for longer than the instructions indicate and rinse your scalp thoroughly when you’re done. This should help minimize your absorption of chemicals and lower the risk of skin irritation.

Try dyes with gentler ingredients. Unlike permanent hair dyes, semi-permanent and temporary dyes contain chemicals that are less harsh and don’t penetrate the hair shaft. Safer yet: Try a plant-based dye, such as henna, Dr. Goldberg said. Though these dyes don’t have the staying power of permanent dyes, they do not appear to be linked to cancer and are less likely than chemical dyes to irritate the skin.