Permanent hair dyes produced before 1980 contained ingredients that are now known to cause cancer. These were eliminated from dyes produced in the United States in 1979, when industry-wide changes in the formulation of hair dyes were instituted.
It has generally been assumed that personal use of today’s hair dyes is safe, even though there is some evidence that at least one cancer causing agent–known as 4-ABP–can be present in some dyes or dye-lots. It is not a deliberate ingredient, but an unintentional by-product of the manufacturing process. Another problematic chemical–known as 2,3-Naphthalenediol–was banned from hair dyes in Europe in 2006, but may be present in some US hair products.
Because of continued concerns about the potential risks of such chemicals, along with the observation that the incidence of a type of cancer known as lymphoma has doubled in the last 20 years–while the popularity of permanent hair dyes has also increased–scientists have investigated whether hair dye increases the risk of lymphoma.
Connections Between Lymphoma and Hair Dye
The term “lymphoma” refers to cancers of the lymphatic system, including Hodgkin’s disease, non-Hodgkin lymphoma, and multiple myeloma. More than 60,000 people in the United States were diagnosed with lymphoma in 2005, and about half of all lymphoma diagnoses and deaths are among women. However, many more women than men use hair dyes.
A study published in July 2006 looked at the relationship between the use of hair dye and development of lymphoma among almost 5,000 people living in 6 European countries. The researchers determined how many of the lymphoma patients had a history of using hair dyes, compared to a similar population that did not have lymphoma.
Many of the media stories about this research, with headlines like “Study Links Hair Dyes to Cancer,” were misleading, considering the actual findings that were reported. The strongest relationship that the researchers found is a 62% higher risk of lymphoma among people who said they had dyed their hair before 1980 but not after. The next strongest is a 37% higher risk among those whose use of hair dyes started before 1980 and continued after that date. Even though these percentages may sound large, they actually represent extremely small increases in individual and population risk. One way to keep this in perspective is to remember that more than 80% of the people who developed lymphoma said they had never used permanent hair dye. Only 4% of those who did have lymphoma used hair dyes prior to 1980.
When looking at a range of cancer types, including lymphoma, there was still a lack of statistically significant evidence linking hair dye use to risk of cancer. In 2008, researcher Michael Kelsh and his colleagues pooled data from 12 different studies (a meta-analysis) of personal hair dye exposure among men and women and bladder cancer. They found that using hair dye did not increase the risk of bladder cancer.
Inconclusive Results for Other Types of Cancers
While most hair dye studies have looked at Caucasian populations, a 2009 study examined the relationship between personal hair dye use and cancer risk by following a group of 70,366 Chinese women. One interesting finding was that women using hair dyes for 20 or more years were at significantly greater risk for ovarian cancer-with nearly six times the risk of non-users. But, it is important to consider that this is based on a small number of long-time hair dye users, and further research is needed. In general, however, no statistically significant evidence was found between the personal use of hair dye and risk for most cancer types.
Other recent studies have produced similar results. A 2007 article by German researchers Hermann Bolt and Klaus Golka analyzed existing evidence and found no bladder cancer risk from permanent oxidative dyes (these are the kind that are mixed right before using). A 2009 study evaluated the association between personal hair dye use and risk of multiple myeloma among U.S. women. Again, no association was found between “ever reporting hair coloring product use” and myeloma risk among all users, including semi-permanent dye users, permanent dye users, and dark permanent dye users.
Ultimately, the results of previous studies on this topic have been inconsistent and though a few have found small increases in cancer risk, the most convincing ones have not. The results of the current studies, however, do underscore the greater toxicity of older dyes compared to newer ones. The bottom line for now, pending additional research, is that people who have been using permanent hair dyes since the 1980s appear to be at little to no increased risk of lymphoma or other cancers.
Sanjose S, Benavente Y, Nieters A, Foretova L, Maynadie M, Cocco PL et al (2009). Association between Personal Use of Hair Dyes and Lymphoid Neoplasms in Europe. American Journal of Epidemiology 164(1):47-55. Retrieved from: http://aje.oxfordjournals.org/cgi/content/164/1/47
Mendelsohn JB, Li Q, Ji B, Shu X, Yang G, Li H et al (2009) Personal use of hair dye and cancer risk in a prospective cohort of Chinese women. Cancer Science, Japanese Cancer Association 100(6):1088-1091. Retrieved from: http://www.statsci.amss.ac.cn/QZLiPage/Publications_files/J2009/J2009CS.pdf
Bolt HM & Golka K (2007). The Debate on Carcinogenicity of Permanent Hair Dyes: New Insights. Critical Reviews in Toxicology 37(6): 521-536. Retrieved from: http://www.informaworld.com/smpp/content~content=a780908126&db=all
Koutros S, Baris D, Bell E, Zheng T, Zhang Y, Holford TR et al (2009). Use of hair colouring products and risk of multiple myeloma among US women. Occupational and Environmental Medicine 66(1): 68-70. Retrieved from: http://oem.bmj.com/content/66/1/68.abstract