Hair Dyes and Cancer Risk What You Need to Know

Fast Facts

Hair dyes are classified into temporary, semi-permanent, and permanent types

Concerns mainly focus on semi-permanent and permanent dyes

Occupational exposure for hairdressers and barbers poses a higher cancer risk

Studies show mixed results on hair dye use and cancer, particularly bladder cancer, leukemias, lymphomas, and breast cancer

Regulatory agencies like IARC and NTP have differing classifications on the carcinogenic potential of hair dyes.

Many people use hair dyes, which contain various chemicals. Research has examined hair dyes as a potential risk factor for different types of cancer. Here’s what the studies show to help you make informed decisions.

Types of Hair Dyes

Hair dyes differ significantly in their chemical composition. There are three main types:

  • Temporary: These dyes coat the hair’s surface but don’t penetrate the hair shaft. They typically last for 1 to 2 washes.
  • Semi-permanent: These dyes penetrate the hair shaft and usually last for 5 to 10 washes.
  • Permanent (oxidative): These dyes cause lasting chemical changes in the hair shaft. They are the most popular because the color remains until the hair grows out. Often referred to as coal-tar dyes due to some ingredients, they contain colorless substances like aromatic amines and phenols, which react with hydrogen peroxide to form dyes. Darker hair dyes generally use more of these chemicals.

Concerns about cancer risk primarily focus on semi-permanent and permanent dyes, especially darker shades due to higher concentrations of certain chemicals.

Exposure to Hair Dyes

When dyeing hair, some chemicals can be absorbed through the skin or inhaled. People working with hair dyes regularly, such as hairdressers and barbers, are exposed more than occasional users. Most cancer-related concerns involve those who frequently work with these products.

Do Hair Dyes Cause Cancer?

Researchers have studied the link between hair dye use and cancer for years, focusing on blood cancers (leukemias and lymphomas), bladder cancer, and breast cancer.

Research Findings

Researchers use two main types of studies to investigate potential cancer causes:

  • Lab Studies: These involve lab animals or cells. Some ingredients in hair dyes (like certain aromatic amines) have been shown to cause cancer in animals given large doses over time. However, these results do not clearly translate to human use.
  • Epidemiologic Studies: These studies examine cancer risk in people, focusing on those who use hair dyes or are exposed to them at work.

Lab Studies

hair dyes and cancer risk"

Some ingredients in hair dyes have been found to cause cancer in lab animals. Although some dye is absorbed through the skin into the bloodstream, most studies have not established a clear cancer risk from skin application in humans.

Studies in People

Research on hair dye users and those exposed at work has produced mixed results:

  • Bladder Cancer: Studies of hairdressers and barbers generally show a small but consistent increased risk of bladder cancer. However, studies of personal hair dye users do not consistently show this risk.
  • Leukemias and Lymphomas: Some studies suggest an increased risk, particularly for non-Hodgkin lymphoma and leukemia, in women using darker dyes, especially before 1980. Results are inconsistent, though.
  • Breast Cancer: Findings are mixed. Some recent studies suggest a link, especially with certain subtypes of breast cancer, but many studies do not show an increased risk.
  • Other Cancers: Insufficient studies exist to draw firm conclusions about other cancer types.

Given the widespread use of hair dyes, more research is needed to clarify these risks.

Expert Agency Conclusions

Several organizations assess environmental substances to determine cancer risk:

  • International Agency for Research on Cancer (IARC): IARC classifies occupational exposure to hair dyes (like in hairdressers) as “probably carcinogenic to humans,” mainly due to bladder cancer risk. Personal hair dye use is considered “not classifiable as to its carcinogenicity to humans” due to insufficient evidence.
  • US National Toxicology Program (NTP): NTP has not classified hair dyes’ overall cancer potential but has labeled some hair dye chemicals as “reasonably anticipated to be human carcinogens.”

Regulation of Hair Dyes

In the US, the FDA regulates cosmetic safety, including hair dyes, but has limited pre-market approval powers. The FDA can act if products are found harmful, including requesting recalls or taking legal action.

Recommendations for Hair Dye Use

While it’s unclear if personal hair dye use significantly raises cancer risk, most studies do not show a strong link. General health recommendations, like not smoking and maintaining a healthy lifestyle, remain important. For those concerned about hair dye safety:

  • Follow package instructions and warnings.
  • Conduct a patch test for allergies before each use.
  • Wear gloves during application.
  • Rinse thoroughly after dyeing.
  • Avoid dyeing eyebrows or eyelashes to prevent eye injury.
  • Avoid dyeing during pregnancy, especially the first trimester.
  • Consider vegetable-based dyes as a safer alternative, though they might not provide lasting color changes.

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