Dec. 14, 2022—Do you use chemical products to straighten your hair? If so, recent headlines about a possible link between the use of hair products and uterine cancer may have grabbed your attention. In recent years, another study has also suggested a link between breast cancer and another hair product: hair dye.

There's a lot we still don't know. But here's a brief look at the findings from these two studies.

Hair straighteners and uterine cancer

The recent study, published in fall 2022 in the Journal of the National Cancer Institute, involved more than 33,000 women who answered questions about their hair products use.

Researchers followed the women for nearly 11 years. They found that:

• Women who straightened their hair more than four times during the year before they entered the study were more than twice as likely to be diagnosed with uterine cancer as women who did not use hair straightening products.
• Using hair dyes, bleaches, highlights or perms did not appear to boost uterine cancer risk.
• Black women had a similar uterine cancer risk to white women in this study. But many Black women are potentially at greater risk due to their higher use of these products (often from an early age), the study authors said.

Hair dyes and breast cancer

In 2019, using data from the same study group as the uterine cancer findings, researchers found that women who use hair dye have a higher risk of developing breast cancer than those who do not. For that study, published in the International Journal of Cancer, researchers reviewed data on 46,709 women who were free of breast cancer but had a sister diagnosed with the disease.

Among their key findings:

• Women who regularly dyed their hair were 9% likelier than women who didn't dye their hair to be diagnosed with breast cancer.
• Black women had the highest increased breast cancer risk linked to permanent hair dye use. Their risk was 45% higher than women who did not use hair dye, compared to 7% for white women.
• Among Black women who used permanent hair dye every five to eight weeks or more, the risk for breast cancer was 60% higher than for women who did not dye their hair.

The fact that hair products marketed to Black women often contain different chemicals than those aimed at white women might account for the difference in risk, the study's authors wrote.

The bottom line

These studies don't prove that dyeing or straightening your hair causes cancer. They only suggest an association between their use and higher risk. Previous studies of hair dyes and breast cancer have yielded mixed results. And the possible ties between uterine cancer and hair products haven't been studied enough.

More studies are needed to find out if hair products cause cancer and, if so, which of the chemicals they contain may be unsafe. Many of these products contain chemicals called endocrine disrupters, which are linked to cancer risk. If you have questions or concerns about your uterine or breast cancer risk or about hair product safety, talk to your doctor.

Whether or not you use hair dyes or straighteners, it's a good idea to talk to your doctor about breast cancer screening tests. Also, be aware of the possible symptoms of uterine cancer, which may include vaginal bleeding after menopause or between periods.

Sources

• American Cancer Society. "Hair Dyes and Cancer Risk." https://www.cancer.org/healthy/cancer-causes/chemicals/hair-dyes.html
• American Cancer Society. "Study Finds Possible Link Between Hair Dye, Straighteners, and Breast Cancer." https://www.cancer.org/latest-news/study-finds-possible-link-between-hair-dye-straighteners-and-breast-cancer.html.
• Centers for Disease Control and Prevention. "Uterine Cancer. What Are the Symptoms?" https://www.cdc.gov/cancer/uterine/basic_info/symptoms.htm.
• Centers for Disease Control and Prevention. "Uterine Cancer. What Should I Know About Screening?" https://www.cdc.gov/cancer/uterine/basic_info/screening.htm.
• International Journal of Cancer. "Hair dye and chemical straightener use and breast cancer risk in a large US population of black and white women." https://onlinelibrary.wiley.com/doi/10.1002/ijc.32738.
• Journal of the National Cancer Institute. "Use of Straighteners and Other Hair Products and Incident Uterine Cancer." https://doi.org/10.1093/jnci/djac165.
• National Institutes of Health. "Hair straightening chemicals associated with higher uterine cancer risk." https://www.nih.gov/news-events/news-releases/hair-straightening-chemicals-associated-higher-uterine-cancer-risk.