Key takeaways
- A large U.S. cohort study (the Sister Study) examined hair dye and chemical straightener use.
- Both were associated with a modestly higher risk of breast cancer.
- The association with hair dye was stronger among Black women. This is observational research and cannot prove cause.
What it is
Hair dyes and chemical straighteners contain a range of chemicals. Researchers have asked whether regular use is linked to cancer risk, and whether the answer differs across groups.
What the evidence says
In a study of a large cohort of women whose sisters had been diagnosed with breast cancer, researchers found that women who used permanent hair dye and chemical straighteners had a higher risk of breast cancer. The increase associated with dye was larger in Black women than in white women, and straightener use was associated with higher risk in both groups.
What the evidence does not establish
Observational studies cannot prove that these products cause cancer, and participants reported their own product use. The study does not identify which ingredient may be responsible.
Who may want to pay attention
People who use these products frequently may wish to discuss their personal risk factors with a clinician and to follow product safety directions and ventilation guidance.
Sources
- 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. View on PubMed
Last reviewed October 2026. Educational information only, not medical advice. Findings from one study or review do not apply identically to every person or product.