Breast Cancer and Hair Dye - What Do Studies Suggest?

Breast Cancer in the United States: An Overview

Breast cancer is the second deadliest cancer in women in the United States.¹ Studies show that breast cancer is linked to both biological and social risk factors, and can be associated with environmental, reproductive, and lifestyle factors.² Until 2012, White women had higher incidence of breast cancer than African American women.³ In 2012, the incidence of breast cancer in African American women and White women converged.³ Notably, the mortality rate from breast cancer is 42% higher in African American women than in White women.³

What does the data tell us?

This section will explore what existing studies have shown regarding hair dyes and breast cancer risk. Chemical compounds like some aromatic amines found in hair dyes are suspected of being carcinogenic.⁴ Permanent hair dyes, which compose roughly 80% of the market, contain para-substituted aromatic amines and meta-substituted aromatic amines that form the hair dye through a chemical reaction with peroxide.⁴ Hair dyes are generally well-tolerated but can cause allergic contact dermatitis.⁵ However, can hair dye use contribute to more sinister pathologies such as breast cancer?

A case-control study involving Finnish women found an association between hair dye use and breast cancer incidence.⁶ Although there were some biases and confounders such as misclassification of hair dye use, non-response bias, and socio-economic factors, this study suggests that the safety of hair dyes cannot be presumed safe and more studies must be done to assess their safety.⁶

The data on hair relaxers is ambiguous. A study of 266,298 person-years follow-up of African American women who used hair relaxers found no increased breast cancer risk from 1997 to 2003.⁷ However, more recent studies show differing observations. A prospective-cohort study found in 2019 that African American women who had a sister with breast cancer and used permanent hair dye were at a 45% higher risk of developing breast cancer, while White women with the same parameters were at a 7% higher risk of developing breast cancer.⁸ Additionally, this study found that both personal chemical straightener and semi-permanent hair dye use were associated with breast cancer risk, with a higher frequency of use increasing risk.⁸ Ultimately, this study found a higher breast cancer risk associated with the use of chemical hair relaxers and permanent hair dyes, suggesting that chemicals in hair products may contribute in breast carcinogenesis.⁸ When comparing the risk of developing breast cancer between hair dye users and non-users, a meta-analysis of studies done between 1980 and 2017 found that hair dye users were at a 18.8% higher risk of developing breast cancer.⁹

Another study observed both hair products use and breast cancer association in both White women and African American women.¹⁰ The study found that White women used hair dyes more frequently than African American women, while African American women used hair relaxers and deep hair conditioners more frequently than White women.¹⁰ This study found that dark hair dyes were associated with higher breast cancer risk in African American women.¹⁰ Interestingly, dark hair dyes were associated with estrogen receptor + (ER+) breast cancer, while relaxer use was associated with estrogen receptor – (ER-) breast cancer.¹⁰

So—now what?

Most studies analyzed in this article found a higher risk of developing breast cancer associated with hair dye and chemical hair straightener use. The risk of developing breast cancer appears to be dose-dependent, and African American women may be at a higher risk. More studies must be conducted to elucidate the risk of breast cancer development with hair dye in terms of frequency of hair dye use, hair dye type, delineation of chemical type to breast cancer risk, and race-dependent risk association.