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Celebrities rarely stick to one hair style or colour for very long. They may be photographed as brunette one week and as a redhead the next. But many people have concerns about the chemicals used in hair dyes. Are they safe for you and your hair?

Did you know? You should not use hair dyes on your eyebrows or eyelashes because some ingredients can cause blindness.Unfortunately, there is no simple answer to that question. A common concern is whether hair dyes contain toxic substances that could cause cancer or other serious health problems. Hair dyes contain either natural chemicals, synthetic chemicals, or a combination of the two. And these substances can be absorbed into the body through the skin, scalp, and hair.

In Canada, cosmetics like hair dyes are regulated by Health Canada, which states that approved hair dyes are safe when used properly. Still, over the years, the safety of various substances used in hair dyes has been questioned, and it is always a good idea to learn more about what you are putting on—and in—your body.

During the 1970s, studies linked aromatic amines, a type of chemical used in permanent hair dyes, to cancer in rodents. In response, the European Union banned some hair dye ingredients and extensive testing was undertaken in labs all around the world. Researchers were especially interested in the link between chemicals used in hair dyes and different forms of cancer in humans, including bladder cancer and non-Hodgkin lymphoma. Whether using hair dye during pregnancy can cause complications or childhood cancer has been another common concern.

Did you know? Before using hair dye, you should apply a small amount behind your ear or on your inner forearm. Don’t use the dye if, after leaving it to dry for 24 hours, you experience any redness, burning, itching, blistering, or skin irritation.The Cosmetic Ingredient Review (CIR) was established by the American cosmetic industry in 1976. Since then, it has assessed the safety of over 1000 ingredients. After reviewing numerous epidemiological studies, the CIR determined that there is no direct link between hair dye use and cancer. The CIR also determined that there isn’t enough evidence to show a direct relationship between childhood tumours and maternal hair dye use.

Doctor Angela Chua-Gocheco and her colleagues at The Hospital for Sick Children in Toronto have reported similar findings. They concluded that limited use of hair dyes (3 or 4 times during pregnancy) is unlikely to harm to the fetus. This particular study also looked at the effects of occupational exposure on pregnant hairdressers. They found minimal toxic effects but still recommended precautions like wearing gloves be taken to minimize exposure.

After extensive study, the cosmetics industry, government regulators, and medical researchers have all concluded that approved hair dyes are safe for both the general public and expectant mothers. So if you are considering a new hair colour, be sure to read the label carefully and keep an eye out for any new research findings.

Learn more!

Online resources

Cosmetics: Hair dyes (2011)

Government of Canada

General consumer information on hair dyes, their labelling, and their safety.

Safety of hair products during pregnancy (2008)

Angela Chua-Gocheco, Pina Bozzo and Adrienne Einarson, Canadian Family Physician 54(10), 1386-1388

Discusses pregnant women's and hairdressers' exposure to potential dangerous ingredients in hair dyes.

Other resources

H.M. Bolt and K. Golka. (2007). The debate on carcinogenicity of permanent hair dyes: new insights. Critical Reviews in Toxicology 37(6), 521-536.

A review of research into potentially dangerous ingredients in permanent hair dyes. An asbtract of the article is available on PubMed. However, a subscription is required to view the full text.

Cosmetic Ingredient Review Expert Panel. (2008). Annual Review of Cosmetic Ingredient Safety Assessments: 2005/2006. International Journal of Toxicology 27 (Suppl. 1), 77-142.

Results of the Cosmetic Ingredient Review program’s research into the safety of hair dye ingredients. An introduction to the article is available on the journal’s website. However, a subscription is required to view the full text.

Catherine Chan

An aspiring science writer with a master's in materials science engineering from the University of Toronto.

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