Introduction
Millions of women and men around the world enhance or change their appearance with hair dye. Hair dye is classified into three major groups — temporary, semipermanent, and permanent. Typically, the process for using a permanent hair colorant consists of mixing colorless dye precursors, which create the basic color when mixed with a stabilizer, such as hydrogen peroxide, and applying the mixture to the scalp and hair. This process results in a series of chemical reactions leading to the production of the final color, which becomes trapped in the hair.
Consumers can choose from hundreds of hair dye products that contain combinations of more than 5,000 different chemicals.1 The types of chemicals can vary by commercial brand and hair color shade. Scientists are working to determine if exposure to any of the hair dye chemicals is associated with an increased risk of cancer or other diseases.
In the late 1970s, some hair dye chemicals were linked with cancer in laboratory animals, so many manufacturers removed these chemicals from their products.1 However, some dyes on the market today contain substances that are in the same chemical class as those removed.
Many salon professionals have expressed concern about the potential cancer-causing nature of hair dye. Some studies have found an increased risk of bladder cancer in hairdressers.2 However, study results are mixed for people who personally use hair dyes, and the link to bladder and other cancers is uncertain.
A study conducted by the International Agency for Research on Cancer, part of the World Health Organization, concluded that occupational exposure to hair dye, such as that experienced by a hairdresser or barber, shows limited evidence in humans for the carcinogenicity, or ability to cause cancer. They also did not find enough evidence to show that personal use of hair dyes causes cancer.3
What is NIEHS Doing?
NIEHS is committed to supporting research to protect the health of people using hair dye and other personal care products.
The NIEHS , along with the National Cancer Institute, have tested 26 chemicals used in hair dyes for potential carcinogenicity in animals. NTP continues to conduct and fund research on chemicals that may be harmful to human health.
Further Reading
Printable Fact Sheets
Additional Resources
- The National Library of Medicine Household Products Database provides information on the health effects of specific hair dye products.
- The U.S. Food and Drug Administration (FDA) offers information about the safety of hair coloring products on its Hair Dyes website.