Does Hair Dye Cause Cancer?

Hair dye is a chemical product. People put it on the scalp, sometimes every few weeks for decades. NCI estimates that 50% to 80% of women in the United States, Japan, and the European Union have used hair dye. When a product is that common, even a tiny effect on risk would add up. That is why researchers keep studying it. It is also why headlines keep landing on both sides.

NCI's fact sheet splits the question in two. That split matters more than anything else here.

• Personal use means coloring your own hair at home, or having it done at a salon a few times a year.
• Occupational exposure means a hairdresser or barber mixing and applying dye all day, for years.

The doses are not close. Neither are the findings.

Permanent dyes make up about 80% of the hair dye sold. They work in two steps. Colorless "dye intermediates" and "couplers" are mixed with hydrogen peroxide. The peroxide makes them react with each other and build pigment inside the hair. Darker shades use more intermediate.

Semi-permanent and temporary dyes skip that reaction. They hold colored compounds that stain the hair directly.

The FDA groups nearly all of these as "coal-tar" hair dyes. The name is a leftover. These colors once came from the coal industry. Most are now made from petroleum.

In 2010, IARC — the World Health Organization's cancer research agency — reviewed the evidence. It concluded that some of the chemicals professional hairdressers are exposed to are "probably carcinogenic to humans." Carcinogenic just means cancer-causing.

Bladder cancer is the strongest thread:

• A 2010 meta-analysis pooled 42 studies. The longer a person had worked as a hairdresser, the more likely bladder cancer was.
• People who had been hairdressers for at least 10 years were nearly twice as likely to get bladder cancer as people who never were.
• A Swedish study split its results by era. It found no raised risk in recent decades.

That last line is the hinge of this whole topic. Our page on bladder cancer covers what that cancer looks like and how it is found.

Early permanent dyes used aromatic amines as intermediates. Some of those are cancer-causing. In the mid- to late 1970s, makers changed their formulas and took several out. NCI is blunt about the limit here: it is not known whether any chemical still used in hair dyes is cancer-causing.

The FDA acted on two ingredients in 1979. Its rule, 21 CFR 740.18, ordered this warning on dyes holding 2,4-diaminoanisole or its sulfate: "Contains an ingredient that can penetrate your skin and has been determined to cause cancer in laboratory animals." The rule is still printed in the Code of Federal Regulations. But it was stayed in February 1982 and never revived. In practice it does not bite, and for a plain reason: the industry stopped using those two chemicals, and the FDA says it no longer sees them in hair dyes.

IARC's overall verdict on personal hair-dye use is "not classifiable as to its carcinogenicity to humans." That means the evidence is not strong enough either way. It is not a clean bill of health.

• Bladder cancer. A 2014 analysis pooled 17 studies and found no sign of raised risk from personal use. For permanent dyes on their own, results are mixed.
• Non-Hodgkin lymphoma. A pooled analysis of four case-control studies found that women who began dyeing before 1980 were 1.3 times as likely to get this lymphoma. Women who began after 1980 showed no rise. A large cohort study in 2020 found no link.
• Breast cancer. Results are mixed, and the newer, larger studies are less reassuring. One study of US women who used dark or permanent dyes compared any use with no use. Risk was 1.07 times higher in non-Hispanic White women and 1.45 times higher in Black women. Some studies find home application carries more risk than salon application.
• Leukemia. A meta-analysis of 20 studies found a small link that was not statistically significant.
• Other cancers. One large cohort found no leukemia link. It did find very slightly higher rates of basal cell skin cancer, mostly in women with naturally light hair, and of ovarian cancer.

This is where the numbers are firmer, and it is not about dye at all. Some straightening and relaxing formulas hold formaldehyde, a known carcinogen, as an active ingredient.

• In a case-control study in New York and New Jersey, White women who had ever used chemical relaxers were 1.7 times as likely to get breast cancer as women who never had. No such link showed up in Black women.
• In a study in Ghana, women who had ever used these products were 1.6 times as likely to get breast cancer.
• In a large US study, women who used straighteners at least once a month in the past year were 1.3 times as likely to get breast cancer.
• In the same group of women, frequent use of straighteners and perms as a teenager was tied to more breast cancer before menopause.
• A large cohort study found that women who had used any straightening product in the past year had 1.8 times the risk of uterine cancer.

Because these products hold different mixes of chemicals, researchers are still working out which ingredient does what.

Coal-tar hair dyes sit in a legal carve-out. Color additives normally need FDA approval before use in cosmetics. Coal-tar hair dyes do not. The FDA also cannot act against one just for holding a harmful ingredient, so long as the label carries a caution statement and directions for a skin test.

That caution statement covers skin irritation and warns that the product must not be used on eyelashes or eyebrows, because doing so may cause blindness. It says nothing about cancer. The FDA's own current line on cancer is narrow and worth reading closely: it does not have reliable evidence showing a link between cancer and the coal-tar hair dyes on the market today.

One practical note the FDA does make: do the skin test before every use, not just the first time. Sensitivity to PPD, a common dye ingredient, can appear after years of trouble-free coloring. Neither the FDA nor NCI publishes a safe number of dye jobs per year, or a gloves-and-ventilation rule for home use.

For occasional personal use, current evidence does not show that hair dye clearly raises cancer risk, and it does not clear it either. For decades of daily salon handling, the bladder cancer evidence is real, though it may reflect older formulas. The sharpest recent findings involve straighteners and relaxers rather than dye. For a wider look at claims like this one, see our guide to common cancer myths.

• National Cancer Institute, Hair Dyes, Other Hair Products, and Cancer Risk, reviewed December 1, 2022, accessed August 6, 2026
• U.S. Food and Drug Administration, Hair Dyes, accessed August 6, 2026
• U.S. Government Publishing Office, 21 CFR 740.18 — Coal tar hair dyes posing a risk of cancer, accessed August 6, 2026