Harvard Study Shows No Link Between Personal Use Of Permanent Hair Dyes And Cancers Or Cancer Mortality In Women
A cohort study by researchers from Harvard Medical School on women in the United States who use permanent hair dye
products to color their hair at home has found that most do not experience greater risk of most cancers or greater cancer related mortality.
The study findings were published in the British Medical Journal. https://www.bmj.com/content/370/bmj.m2942
Although the study findings should provide general reassurance to users of permanent hair dyes, the researchers warned that they did find a slight increase in risk of ovarian cancer and some cancers of the breast and skin but the association was not properly correlated and warrants further studies.
Also the study indicated that natural hair color was also found to impact on the likelihood of some cancers for instance dark hair colours.
The use of hair dye is very popular, particularly among older age groups keen to cover up signs of grey.
It is estimated that hair dyes are used by 50-80% of women and 10% of men aged 40 and older in the United States and Europe.
However the most aggressive hair dyes are the permanent types and these account for approximately 80% of hair dyes used in the US and Europe, and an even greater proportion in Asia.
Although the WHO or World Health Organization's International Agency for Research on Cancer has classified occupational exposure to hair dyes as a probable carcinogen, there is no warning about personal use because existing evidence is inconclusive. https://monographs.iarc.fr/wp-content/uploads/2018/06/mono99-17.pdf
In order to gain a better understanding of the risk of cancer from use of personal hair dye, researchers analyzed data on 117,200 women from the Nurses' Health Study based at Brigham and Women's Hospital, Boston, a large prospective cohort study, which includes assessments of hair dye exposure.
All the women in the study did not have cancer at the start of the study and were followed for 36 years.
The study findings showed no increased risk of most cancers or of cancer death in women who reported having ever used permanent hair dyes compared with those who had never used such dyes.
It was found that the use of hair dye did not increase risk of cancers of the bladder, brain, colon, kidney, lung, blood and immune system, or most cancers of the skin (cutaneous squamous cell carcinoma and melanoma) or breast (estrogen receptor positive, progesterone receptor positive or hormone receptor positive).
However the use of permanent dyes was associated with a slightly increased risk of the basal cell carcinoma of the skin, and this risk was observed to be higher in women with naturally light hair.
There was an uncorrelated increased risk of three types of breast cancer—estrogen receptor negative, progesterone receptor negative, and hormone receptor negative and ovarian cancer also linked to use of permanent dyes, with risk rising according to the cumulative amount of dye women were exposed to. An inc
reased risk of Hodgkin lymphoma was also seen with use of permanent hair dye but only for women with naturally dark hair.
The study explained, "Possible explanations could be that shades of permanent hair dyes are associated with the concentration of ingredients, with darker colors having higher concentrations."
The study team stressed that this is an observational study, so it cannot establish cause. The researchers also point to some limitations, including the lack of racial diversity of study participants, which mainly included white US women with European ancestry, and the possibility that other unmeasured factors, such as use of other products, may have affected the results.
Also assessments of exposure to hair dye stopped relatively early in the follow-up period as some women may have started, stopped or changed their hair dye after this time, and some users of non-permanent hair dyes might have misclassified themselves as permanent hair dye users.
However the study team says their findings "offer some reassurance against concerns that personal use of permanent hair dyes might be associated with increased cancer risk or mortality."
But they stressed that the positive associations for some cancers with different hair color types warrant further investigation.
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