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Study: Hair straightening products linked to small increased risk of endometrial cancer


Many people use products to straighten their hair. Use of these products, especially frequent use, is linked to a small increase in endometrial cancer.  (Posted 4/18/23)

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Hair straightening products linked to small increased risk of endometrial cancer
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Most relevant for: People who use hair straightening products.
It may also be relevant for:

  • healthy people with average cancer risk

Relevance: Medium

Strength of Science: Medium-High

Research Timeline: Human Research

Relevance Rating Details

What is this study about?

Researchers wanted to better understand whether hair straighteners and other hair products increased the risk of endometrial cancer (a type of uterine cancer), the most common gynecologic cancer.

Why is this study important?

The number of cases and deaths from endometrial cancer are rising. Black women are more likely to be diagnosed with and die of endometrial cancer than women of other races.

Hair straighteners and other hair products have been linked to an increased risk of cancers, including ovarian and breast (read more here). Some chemicals in hair products act like and may contribute to increased cancer risk, especially breast cancer and other hormone-sensitive cancers. Other chemicals in hair products are also known to cause cancer. Until now, no studies have looked to see whether there is a link between hair product use and endometrial cancer, another hormone-sensitive cancer.

Hair product use is high in the United States and Europe, with more than 50 percent of people stating that they have used permanent hair dyes. Several studies have shown that Black women and children are more likely than their white counterparts to use hair products that chemically straighten or relax naturally curly hair.  Health effects due to the use of hair products could be more concerning for this population.

Risk factors for endometrial cancer

People can be born with inherited gene mutations that increase the risk of endometrial cancer:

  • (inherited mutations in MHL1, , , or ) is linked to a lifetime risk of endometrial cancer as high as 60%.
  • (inherited mutations in ) is linked to an increased lifetime risk for endometrial cancer as high as 30%.
  • inherited mutations can increase the risk of a rare but particularly aggressive form of endometrial cancer.

Other factors increase the risk for endometrial cancer in the general population and in people at high risk for cancer. These include: 

  • obesity
  • lack of exercise
  • age (risk increases with age)
  • high-fat diet
  • exposure to certain hormones and hormonal medications like tamoxifen. 

Study findings

This study used data from the ongoing Sisters Study, which includes almost 34,000 participants. Participants were asked about their hair product use over 12 months. Hair products included hair dyes, straighteners, relaxers, pressing products, permanents and body waves.

Over almost 11 years, 378 people were diagnosed with endometrial cancer. Among these:

  •  1.2% of people (38 of 3036) who used hair straightening products (straighteners, relaxers or pressing products) had endometrial cancer compared to 1.1% of people (332 of 30,329) who never used hair straightening products.
    • Women reporting using a hair straightener in the previous 12 months had a higher risk of uterine cancer compared to those who did not use a hair straightener. Women with frequent use (defined as more than 4 times in the year) had even greater risk.
  • 1.6% of people (26 of 1,572 people) who reported frequent use (more than 4 times yearly) of hair straightening products had endometrial cancer.
    • The rate of endometrial cancer found in this study group was increased.
  • Use of other hair products including hair dyes, permanents or body waves was not linked to an increased risk of endometrial cancer.

In this study, people who had ever used straighteners were mostly Black women (60%), tended to be younger, and had a higher BMI and lower levels of physical activity than those who never used hair straighteners. This significant difference between participant groups is not fully accounted for by this study.

What does this mean for me?

This study suggests that using hair straightening products has a small affect on the risk of endometrial cancer. However other factors such as long-term use, obesity and inherited mutations have a larger impact on endometrial cancer risk. Speak with your doctor to understand your risk of endometrial cancer and whether you may benefit from additional screening.


Chang C-J, O’Brien KM, Peil AP, et al. Use of Straighteners and Other Hair Products and Incident Uterine Cancer. JJ Natl Cancer Inst (2022) 114(12).

Disclosure: FORCE receives funding from industry sponsors, including companies that manufacture cancer drugs, tests and devices. All XRAYS articles are written independently of any sponsor and are reviewed by members of our Scientific Advisory Board prior to publication to assure scientific integrity.

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posted 4/18/23

Women should be educated on the possible signs of uterine cancer and report any of the following to their doctor: 

  • unusual vaginal bleeding
  • pelvic or abdominal pain
  • bloating
  • abdominal distension
  • difficulty eating
  • increased urinary frequency or urgency
  • pain during sex

Questions To Ask Your Doctor
Questions To Ask Your Doctor

  • Am I at risk for certain cancers due to the hair products I use?
  • Should I be screened more regularly for certain cancers due to the hair products I use?
  • How can I lower my risk for hormone-sensitive cancers?
  • Should I tell you about certain products I use at home that may increase my risk for cancer?
  • Are there other everyday products that can increase my risk for cancer?


Researchers of this study wanted to know

Some hair products contain chemicals that mimic certain hormones that promote the growth of hormone-sensitive cancers. Using these products can increase the risk for certain cancers, especially hormone-sensitive cancers. In this study, the researchers wanted to better understand if hair straighteners, relaxers, pressing products, permanents or body waves were linked to an increase in endometrial (uterine) cancer, which is the most common gynecologic cancer.

Populations looked at in this study

The Sister Study is a cohort that enrolled 50,884 women between 2003-2009. Participants were eligible if they were women between ages 35 to 74 who were free of breast cancer, lived in the United States (including Puerto Rico) and had at least one sister diagnosed with breast cancer.

For this study, researchers excluded women who withdrew their participation, self-reported a diagnosis of endometrial cancer before enrollment, had an uncertain endometrial cancer history, had an unclear timing of diagnosis relative to enrollment, had a hysterectomy before enrollment, did not answer any hair product use questions or did not contribute any follow-up time. As a result, the study included 33,947 eligible women. Many participants had a college degree or higher level of education (56%).

Self-reported ancestry %
White 85.6%
Black 7.4%
Hispanic 4.4%
Other 2.5%

Study design

Participants were asked questions about their use of hair products in the prior month.  This included questions about how frequently they used hair dyes; straighteners, relaxers, or pressing products; and permanents or body waves. Use was self-reported and was not verified by researchers.

The researchers followed each participant for 10.9 years on average, from the time of enrollment until an endometrial cancer diagnosis, a loss of follow-up, the end of follow-up or death.

The researchers then estimated the association between hair product use and endometrial cancer incidence. They adjusted these results based on various factors, including race and ethnicity, educational level, BMI, physical activity, menopausal status at enrollment, whether participants had given birth or never given birth, smoking status, alcohol consumption, oral contraceptive use and duration, use of hormone replacement therapy and age at first menstrual period.

Study findings

  • The endometrial cancer cases that were diagnosed over the course of the study tended to occur among older women with an earlier age of first period, a higher BMI and lower physical activity.
  • The participants who had ever used straighteners were mostly Black (60%) and tended to be younger with a higher BMI and lower level of physical activity than those who had never used hair straighteners.
  • The risk of endometrial cancer was significantly increased among women who had used hair straighteners in the previous 12 months compared to those who never used hair straighteners.
  • Compared to no use of straighteners, frequent use (4 or more times per year) was associated with a statistically significantly higher rate of endometrial cancer than those who never used hair straighteners.
  • In contrast, the use of other hair products, including permanent hair dye, was not associated with an increased rate of endometrial cancer.
  • Researchers observed differences in associations based on physical activity levels and straightener use.
    • Among those who had ever used hair straighteners, there was an increased rate of endometrial cancer in people with low levels of physical activity compared to those with high levels of physical activity.
    • Similar patterns were also observed among people with frequent use, where less physical activity was associated with a higher rate of endometrial cancer.
  • Endometrial cancer rates among those who used hair straighteners did not vary by race and ethnicity or obesity. Moreover, there was no difference in cancer rates by physical activity, race and ethnicity, or obesity for use of permanent dyes, semi-permanent dyes, or hair permanents. Few Black women participated in the study, so further research is needed to understand the impact of hair straighteners on endometrial cancer in Black women.
  • Participants who had ever used straighteners were mostly Black and tended to be younger with a higher BMI and lower level of physical activity than those who had never used straighteners.


  • The effect of hair straighteners was based a small number of endometrial cancer cases.
  • Uterine cancer often takes years to develop, so use over the past year might not relate to the cancer.
  • Several possible other factors including oral contraceptive use and hormone replacement therapy could also affect endometrial cancer rates.
  • The study did not include information on cardiovascular disease, which is known to be common in people with endometrial cancer and the primary cause of death for women in the US.


This is the first study investigating the relationship between hair straightener use and endometrial cancer. Previous studies have demonstrated that exposure to hair straighteners was associated with lower sex hormone levels, elevated risk of uterine leiomyomata (benign fibroids), early age at menarche, and increased risk of breast and ovarian cancer, supporting a potential role of hair straighteners in the growth and incidence of hormone-sensitive cancer and other diseases.

Several chemicals that are often identified in hair straighteners could contribute to the increased endometrial cancer rates observed in this study. Concentrations of parabens (preservatives) in endometrium tissues and phthalates (chemicals used to make plastics more durable) in urine samples were higher in participants with endometrial cancer than in those who did not have endometrial cancer. Chronic exposure to low-dose bisphenol A (a chemical used to develop certain plastics) has been associated with altered menstrual cycles and uterine anatomy in rats, which has been associated with endometrial cancer development and progression. Notably, using these chemicals on your scalp is more concerning since the scalp tends to absorb more chemicals than other skin areas. Scalp skin that is heated or burned by the application of hair straighteners may lead to even higher absorption of these chemicals.


In a group of nearly 34,000 people, researchers found an association between the use of hair straighteners and the incidence of endometrial cancer. This is the first study of its kind, and more research is needed to confirm these findings in different populations, particularly in Black people because of the high prevalence of straightener use.

In this study, the observed effects of using hair straightening products on endometrial cancer were very small. In addition, no increase in endometrial cancer was observed with the use of permanent or semi-permanent hair dyes.

Future studies are needed to identify the specific chemical ingredients that contribute to the increase in endometrial cancer rates. Given the widespread use of hair products and the rising incidence of endometrial cancer, these findings are particularly relevant for public health approaches to reduce endometrial cancer incidence.

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posted 4/18/23

Peer Support
Peer Support

The following organizations offer peer support services for people with or at high risk for endometrial cancer:

Updated: 08/28/2022

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