THURSDAY, Dec. 5, 2019 (HealthDay News) — Permanent hair dye use is associated with an increased risk for breast cancer, especially among black women, according to a study published online Dec. 4 in the International Journal of Cancer.

Carolyn E. Eberle, from the University of North Carolina at Chapel Hill, and colleagues examined the association between hair dye and chemical relaxer/straightener use and breast cancer by ethnicity among 46,709 Sister Study participants, ages 35 to 74 years, who had a sister with breast cancer but were breast cancer-free themselves.

The researchers identified 2,794 breast cancers during a mean follow-up of 8.3 years. At enrollment, 55 percent of participants reported using permanent dye. Permanent dye use was associated with an increased risk for breast cancer in black women (hazard ratio [HR], 1.45; 95 percent confidence interval [CI], 1.10 to 1.90) and white women (HR, 1.07; 95 percent CI, 0.99 to 1.16). Personal straightener use was associated with breast cancer risk among all participants (HR, 1.18; 95 percent CI, 0.99 to 1.41); higher risk was associated with increased frequency (P for trend, 0.02). Increased breast cancer risk was also seen with nonprofessional application of semipermanent dye (HR, 1.28; 95 percent CI, 1.05 to 1.56) and straighteners (HR, 1.27; 95 percent CI, 0.99 to 1.62) to others.

“As hair dye and straighteners are common exposures, these findings have the potential for substantial public health impact,” the authors write.

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