Could the Chemicals In Our Hair Dyes Really Cause Cancer?




For more than a decade, various health agencies, including the National Cancer Institute and American Cancer Society, have issued precautionary warnings that hair dyes might cause cancer. The degree to which chemicals are typically used in the hair-coloring process suggests this could well be the case.

Conclusive evidence on dye carcinogenicity is thin, uncertain, and sometimes contradictory — but people working in the hair salon industry, colorists, in particular, need to at least become educated on the relative risks. Already many salons are offering vegetable dyes as a color alternative, an apparently growing trend in a world focused on more natural approaches to just about everything. But vegetable dyes simply cannot do the same thing as traditional, chemical-based coloring. So which is the right choice for you?

The science of hair color

Use of dark-pigmented permanent dyes decades ago might double the risk of some blood cancers, according to a study conducted at Yale University (Tongzhang Zheng et al., American Journal of Epidemiology 159, no. 2 [January 15, 2004]). But the researchers strongly qualify, “An increased risk of NHL [non-Hodgkin’s lymphoma] was found only among women who began using hair-coloring products before 1980. Hair coloring products have undergone tremendous change over the last 20 years. Since 1980, many carcinogens have been removed from some formulas, which vary depending on whether the dye is permanent, semi-permanent, darker or lighter.”

Breast cancer and bladder cancer are probably not increased with exposure to chemical dyes, according to a review of several studies that cumulatively looked at more than 10,000 women, 4,461 of whom had non-Hodgkin’s lymphoma (Y. Zhang, S. de Sanjose, P. M. Bracci et al, “Personal use of hair dye and the risk of certain subtypes of non-Hodgkin lymphoma,” American Journal of Epidemiology 167, no. 11 [2008]: 1321-1331). Again, only those women who began dyeing their hair before 1980 showed a slightly higher risk of cancer.

There is a measured increased risk in bladder cancer in hairstylists and barbers, which the Working Group of the International Agency for Research on Cancer (IARC) notes may be due to chemicals used in the industry being “probably carcinogenic to humans” (H. M. Bolt and K. Golka, “The Debate on Carcinogenicity of Permanent Hair Dyes: New Insights,” Critical Reviews in Toxicology 37, no. 6 [2007]: 521–536).

It should be noted that dye formulations changed around that time in the late 1970s and early 1980s when dye manufacturers voluntarily removed certain chemicals, including aromatic amines, which research at that time revealed to be carcinogenic in laboratory animals.

Are hair dyes and other salon chemicals in use today any safer?

Critics of the “today’s chemicals are safe” position argue that the effects of newer chemicals may be cumulative but just not yet evident. In other words, ill effects from new formulations may just be a function of time. The question is unanswerable — for now. As are most questions on the roughly 2,000 externally created chemicals typically found in humans all around the world.

Further complicating the study of long-term use of chemical hair dyes is the fact that most dyes contain multiple, sometimes hundreds of, different chemicals in any single treatment. So it’s difficult to isolate any single ingredient or combinations of dye components. And of course, there are other lifestyle factors, such as smoking, that need to be factored out in population studies. That level of data simply does not yet exist.

As for salon workers — and perhaps the people who frequent their establishments — formaldehyde used to straighten hair might offer other things to worry about. The Washington State Department of Labor and Industries, a division of the state’s Division of Occupational Safety and Health, issued a bulletin in late 2010 stating, “Results from recent tests show that several hair straightening products contain enough formaldehyde to pose a health risk to stylists applying the product once or more a day. Formaldehyde is a regulated chemical linked to serious health effects ranging from respiratory irritation to cancer. The risk to your health increases the more exposure you have and the fewer safety precautions you take.”

Further, the chemicals toluene and dibutyl phthalate, in addition to formaldehyde, are routinely used in nail care products, a service often incorporated into hair salons. Toluene can affect the central nervous system, causing fatigue, dizziness, and headache, and phthalates are suspected of causing birth defects.

Minimizing the risk of potentially carcinogenic chemical hair treatments

Given the uncertainty of whether hair dyes and other chemicals used for hair beauty treatments are carcinogenic, many people prefer to err on the side of caution. Those same individuals might otherwise eat organic food, use non-toxic soaps and other cleaners in the home and buy vegetable dye-only clothing.

The U.S Food and Drug Administration provides some suggestions on how to mitigate the risks:

  • Consider delaying dyeing your hair until later in life, when it starts to turn gray.
  • Consider using henna, which is largely plant-based.
  • Be sure to run a patch test for allergic reactions before putting the dye in your hair. Perform this test before every use.
  • Carefully follow the directions on the hair dye package.
  • Wear gloves when applying hair dye.
  • Don’t leave the dye on your head any longer than necessary.
  • Rinse your scalp thoroughly with water after use.
  • Never mix different hair dye products, because you may cause potentially harmful reactions.
  • Never dye your eyebrows or eyelashes, other than with vegetable dyes.

The drawback on hennas and other vegetable dyes is that color intensity is never as great, and you are limited by your natural color as to what new color you can accomplish (blondes can use henna to go red, auburn or brown but not black, and no dark-haired person could possibly achieve blonde). Also, vegetable dyes are not so strongly absorbed that they last much longer than three weeks. And even vegetable dyes can cause an allergic reaction in some individuals.