Healthy people with average cancer risk
People with a genetic mutation linked to cancer risk
Women under 45
Women over 45
People with a family history of cancer
Many women use products to color or straighten their hair. A large U.S. study linked the use of permanent hair dye and straighteners to increased breast cancer risk, particularly among black women. This XRAY reviews the limitations of this study and highlights the need for additional research before accepting these conclusions. (1/29/20)
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Whether using hair dyes or hair straighteners increase breast cancer risk.
Many women in the U.S. regularly use hair dyes and straighteners. Past studies looking at the effect of hair dyes and straighteners on breast cancer have had mixed results, with some showing that hair dye increases breast cancer risk slightly and other finding no increased risk. This study looked at types of hair products among black and white women to help address this question.
Among study participants, 55% reported using hair dye in the 12 months before enrollment.
Among the 46,709 participating women, 2,794 (almost 6 percent) developed breast cancer.
Permanent hair dyes:
Semi-permanent and temporary hair dyes:
There are many limitations of this study including (more details can be found here):
Your breast cancer risk may be increased if you use permanent hair dyes or straighteners; this risk may be greater for black women than white women. The results of this study conflict with the conclusions of some older studies. There are many limitations of this study that suggest the conclusions need to be taken cautiously. Even if true, the effect of permanent hair dye or straightener use would be an increase in breast cancer risk that may have limited real-world impact. Other lifestyle factors (drinking alcohol, obesity in post-menopausal women, exercise, age of first childbirth) have comparable or much greater effects on breast cancer risk.
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No specific guidelines beyond general safety suggestions exist for use of hair dyes and breast cancer.
The FDA suggests these tips to keep you safe when using hair dyes:
The American Cancer Society suggests:
The clinical trial below is broadly studying cancer and the environment and the genetics of cancers:
Inherited gene mutations that increase the risk of breast cancer may also increase risk of other cancers, such as pancreatic cancer. Clinical studies that look at the environmental factors that may alter cancer risk are listed below:
Good Morning America
On average, 13 percent of women in the U.S. will develop breast cancer in their lifetime. These rates can be substantially higher if women have a family history of breast cancer due to inherited mutations in breast cancer genes. Non-Hispanic black women have a lower rate of breast cancer (12.4 percent lifetime) than non-Hispanic white women (13 percent lifetime). However, black women are more frequently diagnosed with more aggressive forms of cancer. Mortality rates are higher in black women than in white women. Differences in screening and treatment delays, whether due to provider bias, insurance availability or other socioeconomic factors are known to contribute to differences in mortality rates.
Other controllable factors may contribute to breast cancer risk. The researchers in this study note that about one-third of women in the U.S. over age 18 use hair dyes. Do hair dyes contribute to breast cancer risk? Prior research has been unclear; several studies have shown no increase in breast cancer risk, while a few studies have found a slight increase in breast cancer risk. Most of these studies did not look at the use of hair straighteners and most did not focus on black women. There have been a few smaller studies that suggested some effect of hair dyes in black women (e.g. Llanos et al., reviewed by XRAYS here in 2017). The researchers of this study hypothesized that women who use hair dyes and/or straighteners would have a higher rate of breast cancer and that black women would have a higher risk of breast cancer because of their use of hair dyes and straighteners.
Whether using hair dyes or hair straighteners increases breast cancer risk.
The 46,709 participants in this study were part of the Sister Study, a national research project that recruited women who were ages 35 to 74 from 2003 to 2009 and who had one or more sisters with breast cancer.
Women who self-identified as non-black Hispanic or other were not included in the statistical analysis because there were too few women to reach a statistically sound conclusion.
At the time of enrollment in the Sisters Study, the participating women had not had breast cancer. The genetic mutation status of participants was not reported.
Each woman was asked questions about their personal and medical history at the time of their enrollment, including about their use of hair products in the prior 12 months. After enrollment, participants were asked annually about their medical history and whether they had been diagnosed with breast cancer (average follow-up time was just over eight years) and had a more detailed follow-up every three years after enrollment.
Diagnosis of breast cancer was self-reported, and then confirmed by examining medical records to determine ER-status and staging of tumors. Women with confirmed cases of ductal carcinoma in situ (DCIS) or invasive cancer were included; women with lobular carcinoma in situ (LCIS) were excluded. Women who had worked professionally in a hair salon were excluded.
Participants were asked by questionnaire whether and how often they had used permanent, semi-permanent or temporary hair dyes or straighteners in the 12 months before enrollment. Their options for answering included:
Participants were also asked how long they used these hair products with options of:
Other questions included whether participants applied hair dyes or straighteners on other people non-professionally, their demographic information (race/ethnicity and age), socioeconomic status, reproductive history, menopausal status and age at menopause, as well as any history of uterine or ovary removal.
Data analysis was performed using the Cox proportional hazard model as a statistical method to determine the risk of breast cancer by age for different variables. Confounding factors (characteristics that depended on the tested factor) were identified and hazard ratios were adjusted for age and identified confounding factors.
55% of women reported using hair dye in the 12 months prior to enrollment in this study:
Among the 46,709 participating women, 2,794 women developed breast cancer (almost six percent):
Permanent hair dyes
Among all participants, a 9 percent increase in breast cancer risk was associated with use of permanent hair dye. Compared to the 13 percent risk of breast cancer in the general population, the risk of breast cancer among women who also use permanent hair dye would be 14.2 percent.
Among white women, use of permanent dye in the 12 months before enrollment was associated with a 7 percent increased risk of breast cancer. Compared to 13 percent risk of breast cancer in the general population, the risk of breast cancer among women who also use permanent hair dye would be 13.9 percent:
Among black women, use of permanent dye in the 12 months before enrollment was associated with a 45 percent increased risk of breast cancer. Compared to 13 percent risk of breast cancer in the general population, the risk of breast cancer among women who also use permanent hair dye would be 19 percent.
It should be noted that the numbers of cases in this sub-group are small:
Semi-permanent and temporary hair dyes
No increase in breast cancer risk was associated with a woman’s use of semi-permanent or temporary hair dyes.
An increased risk of breast cancer was associated with applying semi-permanent dyes to others. This group included few women, making the result uncertain.
Among all of the participants, an 18 percent increase in breast cancer risk was associated with use of hair straighteners after adjusting for confounding factors. Compared to the 13 percent risk of breast cancer in the general population, the risk of breast cancer among women who also use permanent hair dye would be 15 percent.
While the researchers tested for interactions and confounding factors that may have altered the results, they failed to identify genetic mutation status a major confounding factor. The participants were recruited based on their sisters’ being diagnosed with breast cancer. It is possible and reasonable that more than the average number of women in this study may have had an underlying inherited mutation in a gene that is associated with breast cancer. This potential confounding factor makes the reliability of data suspect.
The small size of these populations means that when the subgroups (e.g., women who did or did not use permanent dye) are looked at there are even fewer women in each category. Some sub-groups are very small (e.g., there are only 40 black women with breast cancer who used permanent dye every 5-8 weeks). Small sample sizes result in less statistical confidence in the results.
Also inconsistent is the finding that permanent dyes increased risk to a person they are used on but not when applied to others. Similarly, breast cancer risk was not elevated in women who use semi-permanent dyes (if anything the data shows a decrease in breast cancer risk) but when women apply the same dye to others they observed an apparent increase breast cancer risk. These results seems counter-intuitive and are not explained.
Inconsistency in the overall data suggests the conclusions may not be reliable.
This research suggests that use of permanent hair dyes and straighteners may increase breast cancer risk for women, particularly for black women. There are many limitations of this study that suggest the conclusions need to be taken cautiously. Even if true, the effect of permanent hair dye and straightener use would be an increase in breast cancer risk that may have limited real-world impact. Other lifestyle factors (drinking alcohol, obesity in post-menopausal women, exercise, age of first childbirth) have comparable or much greater effects on breast cancer risk.
Share your thoughts on this XRAYS article by taking our brief survey.