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.
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 uterinecancerby 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 ofcancer,” 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 practicalsense,” Dr McMichael said.1 “The studies that have been published have often been performed by non-dermatologists, and there are fatal flawsin many of the studies, makingit difficult to really assess how much the most likely exposures — chemical treatments — actually increase the risk ofcancer.”
Implications for Patients
Given the lack of definitive evidence on the topic, research suggesting associations between hair products and cancer do not influence Dr McMichael’s recommendations to patients. She does recommend the use of demi- and semi-permanent types of hair color, which are better for the hair shaft than permanent dyes.
“It stands to reason that these dyes would be less problematic systemically as well, but there are not data to support this,” Dr McMichael said. “As far as other chemicals on the hair, I do not recommend less frequent use of chemical relaxers for patients unless there is clinical hair shaft damage, which would be a reason to recommend against using these products.”
Similarly, Dr Zsiros is not currently recommending that patients discontinue the use of such products.
“However, if a patient were to express worry about the potential risks and wanted to make changes, I would suggest — as a preventive measure — reducing exposure to chemical hair straighteners and dyes, particularly if they have a family history of cancer or an elevated risk due to genetic factors, lifestyle choices, and environmental influences,” she said. “Moreover, I would recommend considering other hair care alternatives, such as natural or organic products, and consistently following safety instructions and guidelines provided by the product manufacturers, to reduce potential risks.”
Health care providers can also help increase general awareness about the potential health risks of certain chemicals used in beauty products, according to Dr Llanos.
“Clinicians should consider discussing with their patients the role of endocrine-disrupting chemicals, including parabens, phthalates, phenols, and others, in hair products and other personal care products and how they might contribute to adverse health outcomes,” Dr Llanos said.8,9 “Receiving this critical information from trusted health care providers could make a world of difference in the types of products people use and purchase for their families and could help to reduce the unequal burden of chemical exposures observed among Black women and other women of color, particularly at critical windows of exposure.”
The hair products in question are “important to many women, so it is imperative that better, more specific studies are performed to give women the correct information about risk,” Dr McMichael said.
“More research is needed to confirm these findings and to better evaluate the risk associated with other hair products that are commonly used particularly in racially and ethnically diverse populations,” Dr White said.
There is also a need for research to investigate the specific chemicals in these products that may affect cancer risk.
“The important takeaways for both patients and doctors are to stay aware, keep abreast of new research findings, prioritize transparent communication, and ensure regular health check-ups for ongoing health monitoring,” Dr Zsiros said.
Disclosures: Dr White, Dr Zsiros, and Dr McMichael reported having no relevant disclosures. Dr Llanos is a member of the Science Advisory Panel ofBreast Cancer Prevention Partners and a member of the Advisory Committee of the Campaign for Safe Cosmetics Non-Toxic Black Beauty Project. She has also been retained as an expert witness for litigation matters related to hair product use and cancer.
References
1. Chang CJ, O’Brien KM, Keil AP, et al. Use of straighteners and other hair products and incident uterinecancer. J Natl Cancer Inst. 2022;114(12):1636-1645. doi:10.1093/jnci/djac165
2. White AJ, Sandler DP, Gaston SA, Jackson CL, O’Brien KM. Use of hair products in relation to ovarian cancer risk. Carcinogenesis. 2021;42(9):1189-1195. doi:10.1093/carcin/bgab056
3. NielsenIQ. Attracting Black beauty consumers in 2022. Published September 8, 2022. Accessed July 20, 2023.
4. Eberle CE, Sandler DP, Taylor KW, White AJ. Hair dye and chemical straightener use and breast cancer risk in a large US population of black and white women. Int J Cancer. 2020;147(2):383-391. doi:10.1002/ijc.32738
5. White AJ, Gregoire AM, Taylor KW, et al. Adolescent use of hair dyes, straighteners and perms in relation to breast cancer risk. Int J Cancer. 2021;148(9):2255-2263. doi:10.1002/ijc.33413
6. Coogan PF, Rosenberg L, Palmer JR, Cozier YC, Lenzy YM, Bertrand KA. Hair product use and breast cancer incidence in the Black Women’s Health Study. Carcinogenesis. 2021;42(7):924-930. doi:10.1093/carcin/bgab041
7. Rao R, McDonald JA, Barrett ES, et al. Associations of hair dye and relaxer use with breast tumor clinicopathologic features: Findings from the Women’s circle of Health Study. Environ Res. 2022;203:111863. doi:10.1016/j.envres.2021.111863
8. McDonald JA, Llanos AAM, Morton T, Zota AR. The environmental injustice of beauty products: Toward clean and equitable beauty. Am J Public Health. 2022;112(1):50-53. doi:10.2105/AJPH.2021.306606
9. Johnson PI, Favela K, Jarin J, et al. Chemicals of concern in personal care products used by women of color in three communities of California. J Expo Sci Environ Epidemiol. 2022;32(6):864-876. doi:10.1038/s41370-022-00485-y
