Does Using Hair Dye Increase Your Breast Cancer Risk?

A Q&A on the latest research connecting hair colors and straighteners to breast cancer
woman dyeing her hair

Whether you’re going for silver fox, blond bombshell or purple pixie, dyeing your hair is one of the most common ways to kick-start your style. But a show-stopping hair color may come with a cost: increased cancer risk. 

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Hair dye contains more than 5,000 chemicals. The list includes some known carcinogens (substances that can cause cancer) like aromatic amines, 3-amino-4-methoxyaniline, 2-nitro-4-aminoaniline and 3-nitro-4-hydroxyaniline.  

These chemicals can disrupt the actions and levels of hormones in your body, affecting cancer risk. In this Q&A, cancer specialist Chirag Shah, MD, explains what we know about hair dye and breast cancer risk.  

Q: What do we know about hair dyes and cancer risk? 

A: There’s been mixed data over the years. But there was a relatively large 2019 National Institutes of Health study that looked at this risk in more than 45,000 women. Called the Sister Study, it examined the relationship between breast cancer and the use of hair dye and hair straightener.  

Researchers found that: 

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  • People who used permanent hair dye regularly had a higher risk of developing breast cancer than those who didn’t. (No variation by frequency of use was seen.)
  • Black women may be at higher risk than white women. There was a 45% increased risk in Black women compared to a 7% increased risk in white women.  

Some research has suggested that semi-permanent hair dye may affect breast cancer risk as well. Interestingly, the Sister Study showed while the semi-permanent dye was not associated with risk, those who used semi-permanent dye themselves — without the assistance of a professional hairstylist — had an association with breast cancer risk.  

Some data connects hair dye with other cancers. The most well-studied connection is between bladder cancer and hair dye. Some studies have found that people who use hair dyes routinely as part of their work are at higher risk of developing bladder cancer. A 2006 study, however, did not support it as an important risk factor.

Q: Can dyeing your hair cause breast cancer? 

A: We are exposed to many things in our environment that are potential breast cancer risk factors. Hair dye is just one on the list. What’s most important is looking at all your risk factors and making decisions based on them. Talk to your doctor about your environment, lifestyle, risk factors and family history so you can decide what’s best for you. 

Q: Is hair dye safe for patients with cancer? 

A: We don’t have good data on hair dye use for patients undergoing cancer treatment. The studies we’ve discussed were examining people who were not diagnosed with breast cancer. The available data doesn’t give us a clear answer about current patients. 

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Q: What about chemical hair straighteners and breast cancer risk? 

A: Some chemical straighteners contain formaldehyde, a known carcinogen. The Sister Study looked at hair straighteners and found some increased breast cancer risk associated with them.

Straightener use in the 12 months before enrollment in the study was associated with an 18% higher breast cancer risk, with more frequent use associated with higher risk. For example, those that used straighteners every 5 to 8 weeks had a 31% higher breast cancer risk.

Q. Should you stop chemically coloring or straightening your hair? 

A: If you have concerns about your breast cancer risk when it comes to the use of hair color or straightener, talk to your healthcare provider or a breast cancer specialist. They can walk you through your risk factors and help you figure out what’s best for you.   

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