For personal use, current evidence shows no clear increase in cancer risk: the International Agency for Research on Cancer classes dyeing your own hair as "not classifiable" (Group 3) [1, 2], and in a study of more than 117,000 American nurses followed for 36 years, permanent hair dye did not raise the overall risk of cancer or of dying from cancer [3]. However, long-term work with these products as a hairdresser is classed as "probably carcinogenic" (Group 2A) [1], and some studies, especially of breast cancer, have found a small link with permanent dyes and hair straighteners that is not yet conclusive [3, 4].
Key points
- Dyeing your hair at home: in large studies, the overall risk of cancer was not higher [3], and no link with bladder cancer was found [6].
- Working in a salon: occupational exposure as a hairdresser is "probably carcinogenic", and bladder cancer has been slightly more common in hairdressers who have worked for many years [1, 5].
- Breast cancer: some studies have found a small link with permanent dyes and hair straighteners, especially in Black women; these findings still need to be confirmed [3, 4].
- Today's dyes have changed: several ingredients that caused cancer in animals were removed from hair dye formulas decades ago [2, 9].
What is in hair dye, and what has changed?
There are three main types of hair dye: permanent, semi-permanent and temporary. Most of the dyes used are permanent; they contain substances that react with hydrogen peroxide to form the colour inside the hair shaft [2]. In the 1970s and 1980s, manufacturers removed several ingredients that had caused cancer in animals [2, 9]. Whether any of the chemicals still used are carcinogenic is not known [2].
Using dye at home or working in a salon?
Hairdressers and barbers: the International Agency for Research on Cancer classes their occupational exposure as "probably carcinogenic" (Group 2A) [1, 2]. In a review of 42 studies, the risk of bladder cancer was slightly higher in hairdressers, and higher still in those who had worked for 10 years or more [5]. Part of this evidence comes from years when dyes still contained the older ingredients [5].
Dyeing your own hair: the agency classes this as "not classifiable" (Group 3), meaning the evidence is not enough to reach a judgement [1, 2].
What did the large studies show?
- More than 117,000 American nurses, followed for 36 years: those who had used permanent hair dye did not get cancer more often overall and did not die of cancer more often. The risk of most cancers, including bladder, bowel, lung, melanoma and hormone receptor-positive breast cancer, was not higher. But with heavy, long-term use, a few cancers were slightly more common: a type of skin cancer (basal cell carcinoma), some hormone receptor-negative breast cancers and ovarian cancer. The researchers say these findings need further study [3].
- About 47,000 women whose sister had breast cancer: permanent hair dye was linked to a higher risk of breast cancer in Black women; in white women the increase was very small and uncertain. The more often hair straighteners had been used, the higher the risk of breast cancer [4].
- Bladder cancer: in a review of 17 studies, dyeing your own hair did not raise the risk of bladder cancer [6].
- Lymphoma: in a large study from several countries, a slightly higher risk was seen mainly in women who had started dyeing their hair before 1980, that is, with the older formulas [7].
What should I do? Use hair dye correctly and carefully
If you dye your hair, there is no need to worry or to stop suddenly. One simple step is enough: follow the instructions carefully. The US Food and Drug Administration recommends the following [9]:
- 1
Do a skin allergy test every time
Before each time you dye your hair, test a little of the dye on your skin [9].
- 2
Wear gloves
Wear gloves when applying hair dye; this matters even more for hairdressers who work with dye every day [9].
- 3
Keep to the time and rinse well
Do not leave the dye on longer than the instructions say, and rinse your scalp well with water afterwards [9].
- 4
Do not dye your eyebrows or eyelashes
Keep hair dye away from your eyes and do not use it on eyebrows or eyelashes. If your scalp is broken, irritated or sunburnt, do not use dye or straightener [9].
It makes sense to use permanent dyes and chemical hair straighteners less often, because in studies the small links were seen mostly with heavy, frequent use [3, 4]. For preventing breast cancer, see the better-proven steps too: Can cancer be prevented? and At what age should I start mammograms?
Frequently asked questions
Is dark hair dye more dangerous than light dye?
What about chemical hair straighteners?
In a study of about 34,000 women, using hair straighteners was linked to more uterine cancer, especially when they were used more than 4 times a year; hair dye showed no such link. This was the first study on the question and needs to be repeated [8].
Does hair dye cause blood cancer or lymphoma?
Is it the same for men who dye their hair?
Most studies have been in women. In a review of bladder cancer studies, hair dye did not raise the risk in men either [6].
I am a hairdresser. What should I do?
Occupational exposure as a hairdresser is "probably carcinogenic" [1]. Always wear gloves when working with dye [9] and do not smoke: about half of bladder cancers are linked to smoking, and in smokers the risk is about four times higher [10]. If you see blood in your urine, see a doctor (symptoms of bladder cancer).
Notes for doctors (for physicians)
For physicians
IARC (Monograph 99, 2008). Occupational exposure as a hairdresser or barber: Group 2A; personal use of hair dyes: Group 3 [1, 2].
Nurses' Health Study (Zhang, BMJ 2020). 117,200 women, 36 years: HR for solid cancers 0.98 (0.96 to 1.01), haematopoietic cancers 1.00 (0.91 to 1.10) and cancer death 0.96 (0.91 to 1.02). BCC 1.05 (1.02 to 1.08). Cumulative dose was positively associated with ER-negative, PR-negative and hormone receptor-negative breast cancer and with ovarian cancer; Hodgkin lymphoma was higher only in women with naturally dark hair (70 cases) [3].
Sister Study (Eberle, Int J Cancer 2020). 46,709 women aged 35 to 74 with an affected sister, mean 8.3 years, 2,794 breast cancers; use in the 12 months before enrolment was recorded. Permanent dye: HR 1.45 (1.10 to 1.90) in Black women and 1.07 (0.99 to 1.16) in white women; straighteners 1.18 (0.99 to 1.41) with a significant trend by frequency (P for trend 0.02) [4]. In the same cohort, straighteners and uterine cancer: HR 1.80 (1.12 to 2.88), and 2.55 (1.46 to 4.45) with use more than 4 times a year [8].
Bladder. Hairdressers (42 studies): SRR 1.30 (1.15 to 1.48), and 1.70 (1.01 to 2.88) with ≥10 years of employment; 1.35 (1.13 to 1.61) after adjustment for smoking [5]. Personal use (17 studies): RR 0.93 (0.82 to 1.05); permanent dyes 0.92 (0.77 to 1.09); dark dyes 1.29 (0.98 to 1.71) [6].
Lymphoma (InterLymph). 4,461 NHL cases and 5,799 controls: use starting before 1980 OR 1.3 (1.1 to 1.4), particularly follicular lymphoma 1.4 (1.1 to 1.9) and CLL/SLL 1.5 (1.1 to 2.0); after 1980 only follicular lymphoma with dark dyes 1.5 (1.1 to 2.0) [7].
In practice. There is no evidence of causality for personal use; the associations are small, in subgroups and need confirmation [3, 4]. For hairdressers, recommend gloves [9] and, because smoking accounts for about half of bladder cancers (NIH-AARP: HR for current smokers 4.06), smoking cessation [10].
Related cancer types
Related questions
References
10 referencesShow all references, 1 with a study cardClose the reference list
Numbers in the text, such as [1], refer to these sources. Sources with a “Study card” button are summarised in the site’s evidence library.
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- 10Association between smoking and risk of bladder cancer among men and women
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