This summary table contains detailed information about research studies. Summary tables are a useful way to look at the science behind many breast cancer guidelines and recommendations. However, to get the most out of the tables, it’s important to understand some key concepts. Learn how to read a research table.
Introduction: Research studies show the use of permanent hair dye does not increase the risk of breast cancer.
Prospective cohort studies and a meta-analysis of 14 studies have found no link between hair dye and breast cancer risk.
Learn more about hair dyes, hair relaxers and breast cancer risk.
Learn about the strengths and weaknesses of different types of studies.
See how this risk factor compares with other risk factors for breast cancer.
Study selection criteria: Prospective cohort studies and meta-analyses.
Table note: Relative risk above 1 indicates increased risk. Relative risk below 1 indicates decreased risk.
Study Population(number of participants)
Relative Risk of Breast Cancer in Women who Ever Used Hair Dye Compared to Those who Never Used Hair Dye,RR (95% CI)
Prospective cohort studies
Cancer Prevention Study II (CPS-II) 
573,369(number of cases not given)
Nurses' Health Study 
Shanghai Women's Health Study 
Takkouche et al. 
14 studies including 680,633 women (any hair dye use)
9 studies (permanent hair dye use only)
9 studies(intensive hair dye use)
NS = Not statistically significant
* Study results are from 2 study sites.
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