Hair Dyes and Cancer Risk

Hair dyes are commonly used by many people. These products contain a range of different chemicals. Knowing what research shows about hair dyes as a possible cancer risk can help you make choices that feel right for you.

What are hair dyes?

Hair dyes are products used to change the color of hair. They can contain any combination of thousands of different chemicals.

Ingredients in hair dyes have changed over time. Early hair dyes contained chemicals, including some aromatic amines, that were found to cause cancer in lab animals in the late 1970s. Due to these findings, hair dye manufacturers changed some of the ingredients in their products.

Since the products have changed, studying exposure to hair dyes from decades ago is not the same as studying exposure to today’s products. In fact, many studies classify personal hair dye use based on whether it took place before 1980 or after.

Types of hair dyes

Hair dyes differ in their chemical makeup. The 3 main types of hair dyes are:

• Temporary: Dyes that cover the surface of the hair, but don’t enter the hair shaft. In general, they last for 1 to 2 washings.
• Semi-permanent: Dyes that enter the hair shaft. These dyes don’t lighten the hair, but they can darken it up to 3 shades. These dyes typically last for 6 to 12 washings.
• Permanent (oxidative): Dyes that cause lasting chemical changes in the hair shaft. These dyes are sometimes called coal-tar dyes because of some of their ingredients. They contain colorless chemicals such as aromatic amines and phenols that react with hydrogen peroxide to create color. Darker hair dyes tend to use more of these coloring agents. These are the most popular types of hair dyes, and the color lasts until new growth comes in.

Often, temporary and semi-permanent dyes can be found in gels, lotions, or conditioners with different shades of color.

Most cancer risk concerns have focused on semi-permanent and permanent dyes. Darker dyes may contain higher amounts of chemicals that may cause cancer. These products are considered a greater concern.

How are people exposed to hair dyes?

When hair is dyed, small amounts of chemicals in the dye can be absorbed through the skin or inhaled from fumes in the air. One common ingredient is para-phenylenediamine (PPD), a colorless compound that produces a brown tint when exposed to oxygen or through an oxidizing agent.

People who work with hair dyes regularly, such as hairdressers, stylists, and barbers, are likely to be exposed to the chemicals in hair dye more than people who just dye their hair on occasion. There’s more concern about possible cancer risk from hair dyes for people exposed to them regularly.

What expert agencies say

Several national and international agencies study substances in the environment to determine if they might cause cancer. In general, the American Cancer Society (ACS) does not determine whether something should be considered a carcinogen (something that can cause cancer). Instead, ACS looks to other respected organizations to evaluate the risks based on the available evidence.

Based on studies in people and animals, some of these expert agencies have classified hair dyes or their ingredients according to whether they might cause cancer.

The International Agency for Research on Cancer (IARC) classifies hair dyes as “probably carcinogenic to humans” for people such as hairdressers or barbers who are exposed to dyes in their workplace. This classification is based on data regarding bladder cancer. The evidence for other types of cancer is considered mixed or inadequate.

IARC considers personal hair dye use to be “not classifiable as to its carcinogenicity to humans,” based on a lack of evidence from studies in people.

The US National Toxicology Program (NTP) has not classified the potential of hair dyes to cause cancer. However, it has classified some chemicals that are or have been used in hair dyes as “reasonably anticipated to be human carcinogens.”

For more on the classification systems used by these agencies, see How Do We Know What Causes Cancer? and Known and Probable Human Carcinogens.

Do hair dyes cause cancer?

Some research suggests a possible link between the use of hair dyes and some cancers. Certain studies have found connections to increased risk of blood cancers, such as leukemias and lymphomas, as well as bladder cancer and breast cancer.

What do studies show?

Studying hair dyes can be hard because they aren’t all the same. Researchers use 2 main types of studies to help find out if a substance can cause cancer.

• Lab studies are done using lab animals or cells in lab dishes.
• Studies in people (epidemiologic studies) compare groups to see if people with higher exposures are more likely to develop cancer.

Most often, neither type of study gives a complete answer on its own. Researchers look at evidence from both types of studies when trying to figure out whether something might cause cancer.

Studies done in the lab

Some ingredients used in hair dyes, including certain aromatic amines, have been shown to cause cancer in lab animals. These results were usually seen when animals were exposed to large amounts of chemicals over long periods of time.

Although studies show that some dye applied to an animal’s skin is absorbed into the bloodstream, most have not found a direct link between skin application and cancer risk.

It’s not clear how these lab results might relate to people who use hair dyes.

Studies in people

Most studies looking at hair dyes and cancer risk have focused on certain cancers, such as bladder cancer, non-Hodgkin lymphoma, leukemia, and breast cancer. These studies have looked at 2 groups of people

• People who use hair dyes frequently
• People who are exposed to hair dyes at work, such as hairdressers and barbers

Hair dyes and bladder cancer risk

Most studies of people exposed to hair dyes at work have found a small, but fairly constant, increased risk of bladder cancer.

Studies of people who dye their hair at home have generally not found an increase in bladder cancer risk.

Hair dyes and risk of leukemias and lymphomas

Studies looking at a possible link between permanent hair dye use and the risk of blood cancers such as leukemias and lymphomas have had mixed results.

Some studies have found an increased risk of certain types of non-Hodgkin lymphoma in women who used hair dyes before 1980, mostly with use of dark-colored dyes.

The same types of findings have been reported in some studies of leukemia risk, especially chronic lymphocytic leukemia (CLL), with long-term use of hair dye. But not all studies have found an increased risk.

Hair dyes and breast cancer risk

Studies looking at permanent hair dye and breast cancer risk have also had mixed results. Many studies have not found an increase in risk, although some more recent studies have.

Some studies suggest that frequent use of dark-colored hair dyes may increase the risk of breast cancer in Black women. However, the use of light-colored hair dyes has been linked to increased risk of breast cancer in White women. Also, a greater risk has been linked to women using more than one type of hair dye product.

Hair dyes and the risk of other cancers

For other types of cancer, too few studies have been done to draw any firm conclusions.

Because so many people use or work with hair dyes, continued research is important to better understand whether these products may increase cancer risk.

Are hair dyes regulated?

In the United States, the Food and Drug Administration (FDA) oversees the safety of cosmetics, including hair dyes. However, there are legal limits on what the FDA can do.

Color additives must be approved by the FDA for their intended use before they are used in FDA-regulated products, including cosmetics. As long as 2 conditions are met, the FDA cannot take action against a coal-tar hair dye on the basis that it contains a toxic ingredient that may make it harmful to consumers. The product label must include a special cautionary statement. Also, the hair dye must come with adequate directions telling consumers to do a skin test before they dye their hair.

The FDA can take action if a cosmetic product is found to be harmful or in violation of the law, like being mislabeled or not having required safety warnings.

If cosmetic products, including hair dyes, are found to be unsafe, the FDA can ask the company to recall the product. However, the FDA can’t force a recall. Still, if needed, the FDA can take further steps, such as asking for a federal court order to stop sales, having US marshals seize the product, or starting criminal action.

Should I avoid or limit my exposure to hair dye?

Whether to use, avoid, or limit use of hair dye is a personal choice. While some research shows a possible cancer risk, more research is needed to better understand this.

Some people may choose to avoid or limit hair dye use for other reasons. For example:

• Some ingredients in hair dyes might cause serious allergic reactions.
• Hair dyes may lead to hair loss for some people.
• Some doctors advise women to avoid hair dye during pregnancy, until after the first trimester. There isn’t enough research to know if hair dye is harmful during pregnancy, but this advice is given just to be safe.

Safety standards for hair dye use

For people who want to dye their hair but are concerned about safety, the FDA has some guidelines:

• Follow the directions in the package. Read all “Caution” and “Warning” statements carefully.
• Do a patch test on your skin before every use to check for an allergic reaction. Some allergies develop over time.
• Wear gloves when applying hair dye. After using it, rinse your scalp well with water.
• Don’t leave the dye on longer than the directions say you should.
• Never use hair dye to dye your eyebrows or eyelashes. It can injure your eyes and may cause blindness. The FDA does not approve hair dye for this use.
• Avoid scratching or brushing your scalp for 3 days before using hair dyes. Don’t dye your hair if your scalp is irritated, sunburned, or damaged.
• Wait at least 14 days after bleaching, relaxing, or perming your hair before using hair dye.

Keep hair dyes out of the reach of children.

Hair dye use during cancer treatment

If you are getting chemotherapy or other cancer treatments, it’s best to avoid exposure to hair dye chemicals during treatment and then for about 6 months after treatment. This allows the scalp and hair to get stronger to withstand the chemicals in hair dyes.

Safer hair color options

Some hair dyes are made from plant-based ingredients like henna or indigo. They may be less likely to irritate your scalp. These products may have limits. They may not be able to change hair color very much. Their color may fade faster than permanent dyes (unless they contain some of the same ingredients as permanent dyes). However, they may be a good option for people concerned about hair dye safety.

Even though these products are thought to be safer, it’s still important to read labels carefully for ingredients and to follow the directions for use.