Hair Products May Increase the Risk of Certain Cancers

Black woman getting her hair done at a Black-owned business
Black woman getting her hair done at a Black-owned business
Research has suggested that hair dyes, straighteners/relaxers, and permanents/body waves may increase the risk of breast and gynecologic cancers.

Multiple studies have linked certain hair products with breast and gynecologic cancers, but it hasn’t been clear if these products are actually causing the cancers.1,2, 4-7

Research has suggested that long-term use of hair dyes, straighteners or relaxers, and permanents or body waves may be associated with increased risks of breast, ovarian, and uterine cancers, said Adana A.M. Llanos, PhD, associate professor of epidemiology in the Mailman School of Public Health at Columbia University Irving Medical Center in New York, New York.

However, many of these studies have design issues that make it difficult to establish a causal link, according to Emese Zsiros, MD, PhD, chair of gynecologic oncology at Roswell Park Comprehensive Cancer Center in Buffalo, New York.

Hair Products Linked to Gynecologic Cancers

In a study published in 2022, researchers followed 33,947 participants (aged 35-74 years) from the Sister Study for an average period of 10.9 years and found that any self-reported use of hair straightening products in the previous 12 months was associated with a higher incidence of uterine cancer compared to never use (hazard ratio [HR], 1.80; 95% CI, 1.12-2.88).1 The incidence of uterine cancer was especially high among participants who used these products more than 4 times in the prior 12 months (HR, 2.55; 95% CI, 1.46-4.45; Ptrend =.002).

“Specifically, we estimated that 1.64% of women who never used hair straighteners would go on to develop uterine cancer by the age of 70, but that risk goes up to 4.05% for frequent users,” said study author Alexandra White, PhD, head of the Environment and Cancer Epidemiology group at the National Institute of Environmental Health Sciences in Research Triangle Park, North Carolina.

“The use of other hair products, such as hair dyes and permanents or body waves, was not associated with an increased incidence of uterine cancer,” Dr White noted.

In a study published in 2021, Dr White and colleagues linked the use of hair straightening products more than 4 times in the past year with an increased risk of ovarian cancer (HR, 2.19; 95% CI, 1.12–4.27).2 That study also showed that any use of permanent hair dye during the past year was positively associated with non-serous tumors (HR, 1.94; 95% CI, 1.12–3.37) and inversely associated with serous tumors (HR, 0.65; 95% CI, 0.43–0.99; P =.002).

Dr White noted that potential risks associated with such hair products may have a greater impact on Black women due to a higher frequency of use in this population.

“Given that these products often contain endocrine-disrupting chemicals and carcinogenic compounds, the disproportionately high use of hair products and other personal care products among Black women — who spend upwards of $7 billion per year on beauty products — contributes to an unequal chemical burden,” Dr Llanos said.3

Hair Products Linked to Breast Cancer

Researchers have also identified associations between the use of some hair products and an increased risk of breast cancer as well as distinct clinicopathologic features in breast tumors.4-6

A study of 46,709 participants from the Sister Study showed a higher risk of breast cancer among participants who used permanent hair dye.4 The risk was seen in Black women (HR, 1.45; 95% CI, 1.10–1.90) and White women (HR, 1.07; 95% CI, 0.99–1.16; P =.04).

The study also showed an increased risk of breast cancer among all participants with a history of chemical hair straightener use (HR, 1.18; 95% CI, 0.99–1.41), especially among those with greater frequency of use (Ptrend =.02). Applying these products to others in a non-professional capacity was also associated with an elevated risk of breast cancer.

Other recent findings from 47,522 patients enrolled in the Sister Study suggested a higher risk of premenopausal breast cancer in association with the frequent use of hair straighteners/relaxers (HR, 2.11; 95% CI, 1.26-3.55) and perms (HR, 1.55; 95% CI, 0.96-2.53) in adolescence (ages 10-13).5

The use of permanent hair dye was not associated with breast cancer overall in this study. However, permanent hair dye was associated with a higher risk of breast cancer among Black women (HR, 1.77; 95% CI, 1.01-3.11).

A study of 50,543 Black women published in 2021 showed that frequent and long-term use of hair relaxers containing lye was linked to an increased risk of estrogen receptor-positive breast cancer (HR, 1.32; 95% CI, 0.97-1.80).6  

In a study of 2998 breast cancer patients published in 2022, Dr Llanos and colleagues found that the application of permanent hair dyes was associated with increased odds of poorly differentiated tumors among Black women.7 This association was seen with home application of hair dye (odds ratio [OR], 2.22; 95 % CI, 1.21-5.00) or a combination of salon and home application (OR, 2.46; 95 % CI, 1.21-5.00).

The study also suggested that relaxer use was associated with larger tumor size. There was a significant association between tumor sizes of 1-2 cm and using relaxers for more than 10 years (OR, 1.72; 95% CI, 1.04-2.87) or using relaxers before age 12 (OR, 1.65; 95% CI, 1.02-2.68).

Correlation vs Causation

Though multiple studies have shown correlations between hair products and cancers, we cannot draw firm conclusions from these findings, according to Dr Zsiros.

“Despite the fact that some hair products may contain potentially harmful chemicals, establishing a direct causal link to cancer development requires more comprehensive scientific evidence,” she explained.

Dr Zsiros noted that some of the studies on the topic have design issues. For instance, multiple analyses include participants from the Sister Study who have a sibling with breast cancer and may therefore have an elevated risk of cancer themselves.1,2,4,5

“The connection between the usage of hair products and the development of cancer could also be influenced by other variables, including genetic factors, lifestyle, and environmental exposures,” Dr Zsiros explained.

“There has not been a separation of different kinds of exposures and the outcome of cancer,” added Amy McMichael, MD, chair of the dermatology department at Atrium Health Wake Forest Baptist Medical Center in Winston-Salem, North Carolina.

“For instance, one paper puts straightening tools like flat irons on the same level as chemical straightening in terms of the associated cancer risk, but this does not really make practical sense,” Dr McMichael said.1 “The studies that have been published have often been performed by non-dermatologists, and there are fatal flaws in many of the studies, making it difficult to really assess how much the most likely exposures — chemical treatments — actually increase the risk of cancer.”

This article originally appeared on Cancer Therapy Advisor