4 December 2019

A new study by the National Institute of Health (US) suggests that using permanent hair dye and chemical straighteners could increase a woman’s breast cancer risk by up to 45%.

The study tracked 46,709 American women for an average of 8.3 years. All participants had a sister diagnosed with breast cancer but didn’t have breast cancer themselves when they enrolled in the research. When joining the study, women were asked about their hair product use over the previous 12 months. Researchers wanted to know if and how often the women used relaxers, permanent, semi-permanent and temporary dyes, and if they were applying these products to someone else.

They found that permanent hair dye use was linked to a 45% higher breast cancer risk in black women and a 7% higher risk in white women. Use of chemical straighteners was linked to an 18% increase in breast cancer risk.

Researchers didn’t have the information on the chemical components of the products used by these women and don’t give any suggestion as to why these hair products might increase breast cancer risk.

These findings disagree with results from some previous studies in this field, and somore research is needed to fully understand the relationship between hair products and breast cancer risk.

Dr Kotryna Temcinaite, Research Communications Manager at Breast Cancer Now, the research and care charity, said:

While this study suggests hair dyes and chemical straighteners could be linked to a higher risk of breast cancer, the overall evidence remains inconclusive and we’d urge women not to worry on account of these results.

This is a large study, but we need to bear in mind that all participants had a family history of breast cancer, which could put them at increased risk of the disease. It is also unclear what specific products women used, or how long they used them for, so it is difficult to draw any direct conclusions on this study alone.

More research is now needed to understand how different compounds found in common hair products could potentially be involved in the development of breast cancer.  What we already know is that all women can help keep their breast cancer risk as low as possible by maintaining a healthy weight, keeping physically active and drinking less alcohol. Even small changes are a great start.

In the meantime, anyone concerned about their breast cancer risk can call our free Helpline on 0808 800 6000.

These findings were published in the International Journal of Cancer.