What is the effect of hair dyes and chemical hair relaxers on breast cancer risk?

Updated: Dec 16, 2019
  • Author: Jessica Katz, MD, PhD, FACP; Chief Editor: Marie Catherine Lee, MD, FACS  more...
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A study of 4,285 women found a significant increase in breast cancer risk in black women who used dark shades of hair dye and in white women who used chemical hair relaxers. The risk of breast cancer was 51% higher in black women who reported using dark hair dye, compared with those who did not, and was 74% higher in white women who reported using chemical relaxers. Risk was more than doubled in whites who used both relaxers and hair dyes (odds ratio [OR] = 2.40, 95% confidence index [CI],1.35–4.27). [42, 43]

In white women,the use of dark hair dyes was associated with increased estrogen receptor (ER)–positive disease (OR = 1.54; 95% CI, 1.01–2.33). Relaxer use was associated with increased ER-negative disease (OR = 2.56; 95% CI, 1.06–6.16). [42]

Similarly, data from 46,709 women in the Sister Study showed an increased risk for breast cancer in women who frequently use permanent hair dye and chemical hair straighteners. Women who regularly used permanent hair dye in the year prior to enrolling in the study were 9% more likely to develop breast cancer, compared with women who did not use hair dye. In African-American women, using permanent dyes every 5 to 8 weeks or more often was associated with a 60% increased risk of breast cancer as compared with an 8% increased risk for white women. Use of semi-permanent or temporary hair dye was associated with little to no increase in breast cancer risk. [44]

Women who used hair straighteners at least every 5 to 8 weeks were about 30% more likely to develop breast cancer. The association between straightener use and breast cancer was similar in African-American and white women, but straightener use was much more common in African-American women. [44]

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