Hair dyes unlikely to increase risk of most cancers in women, finds study
Women who regularly use hair dyes are unlikely to face a higher risk of most cancers and dying from the disease, new evidence suggests. Though the study offers some respite, users may experience a slightly increased risk of developing some forms of cancer, according to experts involved in the study.
The study is observational, meaning it only shows a link between hair dye use and cancer and therefore does not prove that link. "The investigators have studied the association between self-reported personal use of hair dyes and cancer," Dr Paul Pharoah, professor of cancer epidemiology, University of Cambridge, said in a statement. "The headline result is that overall there is no difference in the rate of cancer, in general, in women who have used hair dyes and those that have not," Pharoah, who was not involved in the study, said.
According to estimates, more than one-third of women over the age of 18 and about 10% of men over 40 use some type of hair dye. "Among modern hair dyes, permanent hair dye is the most popular type," Dr. Yin Zhang from Harvard Medical School, and the lead author of the study, told MEA WorldWide (MEAWW). "lt is the most aggressively and extensively used type, and has posed the greatest potential concern about cancer risk. Monitoring and investigating the carcinogenic hazard to people from personal use of permanent hair dyes has major public health implications."
While occupational exposure to dyes is considered a carcinogen [a substance that can cause cancer], the link between the personal use of hair dyes and cancer risks is unclear," Dr Zhang added.
In this study, researchers from the US and Austria studied 117,200 female nurses aged between 30-55 years and followed them for 36 years. None of the participants had cancer at the start of the study. For over the study period, the participants were sent questionnaires on their diet every two or four years. Researchers also gathered information on the nurses' history of hair dye, including updates every two years.
They found that no link between cancer risks and permanent hair dyes for cancers of the bladder, brain, colon, kidney, lung, blood and immune system, or most cancers of the skin or breast. But they did record a slight increase in the risk of ovarian cancer, basal cell carcinoma of the skin and three types of breast cancer — estrogen receptor-negative, progesterone receptor-negative and hormone receptor-negative. But why hair dyes appear to raise odds of some forms of cancer are not clear and needs investigation, Dr Zhang said.
And for women with naturally dark hair, the researchers recorded a slightly higher risk of Hodgkin lymphoma. "Possible explanations could be that shades of permanent hair dyes are associated with the concentration of ingredients, with darker colors having higher concentrations," the authors said.
Pharoah said that evidence linking hair dyes to a slightly higher risk of certain forms of cancer was not compelling. "None of the findings reported in this manuscript suggest that women who use hair dye are putting themselves at increased risk of cancer." Dr Michael Jones from the Institute of Cancer Research, London said that the results are generally reassuring for women who have used personal permanent hair dye in the past.
The authors acknowledged a few limitations, including a lack of racial diversity. Further studies can look at more diverse populations, and evaluate cancer risk between personal use versus occupational use, and between dark-colored versus light-colored permanent dyes, Dr Zhang explained. Nevertheless, the authors said their findings "offer some reassurance against concerns that personal use of permanent hair dyes might be associated with increased cancer risk or mortality."
The study is published in BMJ.