True or False: Hair Dye Causes Cancer
The incidence of certain
Evidence for the Health Claim
Some studies examining the claim that hair dyes increase the risk of certain types of cancer have found a link. In the 1970s, researchers at the National Cancer Institute discovered that rats fed large doses of hair dye ingredients (including substances found in coal tars, which are used for dark-colored dyes) were more likely to develop cancer than rats left unexposed to these substances. The FDA responded by requiring a warning label to be placed on dyes containing certain substances, and many manufacturers stopped using these ingredients. However, some scientists fear that replacement compounds may have similar chemical structures and cause comparable reactions in the body.
American Journal of Epidemiology
recently published a study suggesting that people who frequently used permanent, dark-colored hair dyes before 1980 (which is when the ingredients changed and coal tar was removed) were at a slightly elevated risk for developing
Evidence Against the Health Claim
Research published in the Journal of the American Medical Association (JAMA) in 2005 collected numerous studies that focused on a possible relationship between hair dye and cancer. Two types of studies were analyzed: (1) Case control studies compared hair dye use among people diagnosed with a specific cancer to a comparable sample of hair dye users without cancer. (2) Cohort studies focused on groups of people who did or did not use hair dye, and followed them over time to see who developed cancer.
The analysis found no link between hair dye and
Close examination also found that rates for some of the cancers thought to be linked to hair dye, such as non-Hodgkin’s lymphoma, increased in men. This is another indication that hair dye exposure is probably not the underlying reason, because significantly more women use hair dye than men, and if hair dye was causing the cancers, an increase in incidence in women would be expected, not men.
The analysis also found that the majority of studies examined did not adjust for factors such as smoking, which is a major risk factor for cancer. If, for example, people who smoke are more likely to dye their hair (or vice versa), than the results would have to be interpreted differently.
The effect of this study, therefore, was to discredit the link between cancer risk and hair dye use.
An analysis of the many studies examining a possible link between hair dye use and cancer was unsupportive of a cause and effect relationship. Although it remains unlikely, there could still be a small risk associated with certain cancers. More studies focusing on hairdressers, who are routinely exposed to the chemicals in hair dyes, may shed more light on a possible connection with cancers.
Hair dye is unlikely to be a significant risk factor for cancer, if it is one at all. Family history, diet, smoking, and exercise have far more to do with cancer risk than whether or not you choose to be a brunette or a blonde.
Can hair dye cause non-Hodgkin lymphoma? Study suggests link, but results not conclusive. American Cancer Society website. Available at: http://www.cancer.org/docroot/NWS/content/NWS_2_1x_Can_Hair_Dye_Cause_Non-Hodgkin_Lymphoma.asp . Accessed November 10, 2008.
Does hair dye cause cancer? Cancer Research UK website. Available at: http://www.cancerhelp.org.uk/help/default.asp?page=4124#bladder . Accessed November 10, 2008.
Duenwald M. Study links some hair dyes to kind of cancer. The New York Times website. Available at: http://query.nytimes.com/gst/fullpage.html?sec=health&res=9B0CEFD71E39F937A15752C0A9629C8B63 . Accessed November 10, 2008.
Gago-Dominguez M, Castelao JE, Yuan J, et al. Use of permanent hair dyes and bladder-cancer risk. Int J Cancer . 2000;91(4):575–579.
Kelsh MA, Alexander DD, Kalmes RM, Buffler PA.Personal use of hair dyes and risk of bladder cancer: a meta-analysis of epidemiologic data. Cancer Causes Control. 2008 Aug;19(6):549-58. Epub 2008 Feb 20.
Patlak M. Hair dye dilemmas. US Food and Drug Administration–FDA Consumer website. Available at: http://www.cfsan.fda.gov/~dms/cos-818.html . Accessed November 10, 2008.
Takkouche B, Etminan M, Montes-Martínez A. Personal use of hair dyes and risk of cancer–a meta-analysis. JAMA . 2005;293(20): 2516-2525.
Image Credit: Nucleus Communications, Inc.
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