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More than 33 percent of women over 18 and 10 percent of men over 40 use hair dye, so the question of whether hair dye causes cancer is important.

Research studies are contradictory and inconclusive. However, based on the available research, it appears unlikely that dyeing your hair significantly increases your cancer risk.

In 2010, the International Agency for Research on Cancer concluded there wasn’t enough evidence to determine if the personal use of hair dye increases the risk for cancer.

Since then, more research has been done, and things have become a little clearer.

Hair dyes once contained chemicals that were known to be carcinogenic in animals. Between 1980 and 1982, all hair dyes were reformulated to exclude these chemicals.

However, there are still thousands of different chemicals hair dye manufacturers may use in their products. It’s possible that some might be carcinogenic.

The more you are exposed to a carcinogen, the more likely you are to develop cancer. Factors related to the amount of exposure you have to the chemicals in hair dye include the following.

risk factors for cancer from hair dye
  • Exposure type. People who work with hair dye for a living, such as hairstylists and barbers, have a lot more exposure than people who get their hair dyed.
  • Length of use. People who started dyeing their hair before hair dyes were reformulated in 1980 have been exposed to more potential carcinogens than those who started later.
  • Frequency. The more often you dye your hair, the more often you’re exposed to the chemicals in it.
  • The color of hair dye. Dark hair dye colors like black and brown contain more of the chemicals that might be carcinogenic than light colors.

Researchers have recently found that genetics may be another factor affecting risk of cancer related to hair dye.

Blood cancers

According to the American Cancer Society (ACS), some studies have suggested hair dyes slightly increase the risk of non-Hodgkin’s lymphoma and leukemia in women, but most of these women started dyeing their hair before 1980 using darker dye colors. Other studies suggest there is no relationship between hair dye and these cancers.

More recently, a 2017 study showed there was no significant link between hair dye and leukemia. On the other hand, a 2018 review of available studies suggests there may be a slight increase in the risk for non-Hodgkin’s lymphoma in women who use hair dye, mainly those who had used it 20 years or more.

Bladder cancer

Older studies have found a small increased risk of bladder cancer in people who worked with hair dye on a regular basis. The research isn’t conclusive, because the studies include a lot of people who started using hair color before 1980.

A more recent review of all available studies provided strong evidence that using hair dye doesn’t increase your risk for bladder cancer.

Breast cancer

A 2017 study suggests that there is a connection between dark hair dyes and breast cancer in African American women. But the researchers themselves caution that the study had limitations, so further research is needed to support the results.

Prostate cancer

A 2016 study found that hair dye may increase a person’s risk for prostate cancer. However, experts believe this study isn’t valid because of problems in how it was performed and interpreted.

There aren’t any other studies on hair dye and prostate cancer, so there’s no evidence hair dyes are associated with prostate cancer.

Hair dyes come in two forms that differ in how they change hair color and how long the color lasts:

Oxidative (permanent) hair dye

Oxidative hair dye must be activated by mixing an oxidizing agent (developer) like hydrogen peroxide with ammonia and a coloring agent.

Ammonia opens the outer layer of the hair shaft. The oxidizing agent then enters the hair shaft and removes the natural pigments while bonding the new pigments to the hair shaft. This permanently changes your hair color.

Non-oxidative (semipermanent and temporary) hair dye

Non-oxidative hair dye doesn’t use a developer. It simply coats or stains the hair shaft. Because this type of dye can’t remove natural hair pigments, they can’t make your hair lighter, only darker.

There are two types:

  • Semipermanent. These dyes move a short distance into the hair shaft. It washes out after a few weeks or about five washes.
  • Temporary. These dyes are designed to disappear after one wash. Examples are Halloween spray color and hair chalk.

Oxidative hair dyes have more chemicals than non-oxidative ones. They are stronger and more likely to irritate your scalp. This creates an entry point for the dye to get into your body. So if some chemicals are carcinogens, the risk of cancer is higher with oxidative hair dyes than with non-oxidative hair dyes.

Bleach vs. dye

Bleach is an oxidizing agent. It strips the pigments from your hair, lightening it. Semipermanent and temporary hair dyes don’t have oxidizing agents, so they can’t lighten your natural hair color.

Hair dyes are a mixture of oxidizing agents, ammonia, and coloring agents. They are the opposite of bleach because they add pigments to your hair. The oxidizing agent in the hair dye usually removes the natural pigment before adding the new pigment.

Henna

Henna is a natural plant-based hair dye that lasts about six weeks.

Organic (but not chemical-free)

You can buy organic hair dyes, but they have to contain some chemicals to work, usually synthetic substances. The other natural ingredients may be easier on your hair, but the chemicals have the same potential to cause cancer as those in regular hair dyes.

Graphene

Graphene is the newest nontoxic hair dye alternative. Spraying or combing it into your hair leaves a coating of color.

Unlike hair dye, it doesn’t chemically damage your hair, and it lasts for over 30 washes. The disadvantage is that it only comes in black and brown.

With the possible exception of some types of non-Hodgkin’s lymphoma, there’s no strong evidence linking personal use of hair dye and cancer. If there is an increased risk of cancer, it’s minimal.

If you’re concerned, limiting the frequency and number of years you use hair dye, especially dark colors, will reduce your risk.