There is conflicting research on whether exposure to the chemicals used in hair dye is associated with an increased risk of cancer, but some recent studies have noted a potential link.
Read on to learn about what the research says about hair dye and cancer.
Is Dyeing Your Hair Bad?
Whether or not dyeing your hair is bad can’t be answered without considering the many different factors.
Some of the more than 5,000 chemicals in hair products have been found to induce tumors in rats. Some also contain mutagenic (capable of causing a change in the DNA of a cell) and endocrine-disrupting (interfere with hormones) properties. Some chemical straighteners also contain formaldehyde, which is a carcinogen (capable of causing cancer).
However, it isn’t always as simple as looking for formaldehyde or methylene glycol on the product labels. Synonyms may be listed, such as:
FormalinMethanalMethanediolFormaldehyde monohydrate
Products may also contain chemicals that release formaldehyde when they are heated (such as when using a flat iron or blow dryer). These include:
Timonacic acidDimethoxymethaneDecamethyl-cyclopentasiloxane
Small amounts of some chemicals may be absorbed through the skin or inhaled from fumes while dyeing your hair, having your hair dyed, or dyeing someone else’s hair.
Hairdressers and other professionals who regularly work around hair dyes may have a higher exposure to these chemicals than those who occasionally use hair dye for personal use.
Most research so far has not found a conclusive link between personal hair dye use and cancer but rather notes the potential.
The World Health Organization’s International Agency for Research on Cancer (IARC) has determined that chemical exposure at work for these professionals is likely carcinogenic (based on bladder cancer data specifically). In terms of personal hair dye use, the IARC determined it can’t be classified as carcinogenic to humans, due to the lack of evidence from human studies.
The U.S. government’s National Toxicology Program (NTP) has not classified exposure to hair dyes as having (or not having) the potential to cause cancer, but has deemed some chemicals that are now or were previously used in hair dyes to possibly be human carcinogens.
Types of Hair Dyes
There are three main types of hair dyes:
Permanent (oxidative): Sometimes referred to as coal-tar dyes. Uses chemical reactions between hydrogen peroxide and substances such as aromatic amines and phenols to create lasting chemical changes in the hair shaft. Semi-permanent: Doesn’t penetrate into the hair shaft. Usually washes out in five to 10 washings. Temporary: Doesn’t penetrate into the hair shaft (covers the surface of the hair). Typically washes out in one to two washings.
What Researchers Know About Hair Dye and Cancer
Most of the studies examining a possible risk between hair dye and an increased risk of cancer have focused on specific cancers, such as:
Bladder Non-Hodgkin lymphoma Leukemia Breast cancer
These studies typically considered the potential effects on people who regularly use hair dye and/or people who work with hair dyes.
Some of these studies have shown an increased risk of certain cancers with personal hair dye use, but others have found conflicting results.
A 2020 study of over 117,200 women in the United States found an association between hair dyes and an increased risk of some cancers, including:
Basal cell carcinoma (in women with naturally light hair) Breast cancer (estrogen receptor negative, progesterone receptor negative, hormone receptor negative) Ovarian cancer Hodgkin lymphoma (in women with naturally dark hair)
The study found no increase in risk for most cancers (other than the ones listed) or cancer-related mortality for personal users of permanent hair dyes.
Hair Dye, Straighteners, and Breast Cancer
A 2019 study examined a possible link between breast cancer and hair dye and hair straighteners. The study included 46,709 women in the United States who had no history of breast cancer at the time of the study enrollment, but had at least one sister who had received a breast cancer diagnosis.
The study found that the women who regularly used permanent hair dye during the year prior to the study were 9% more likely to develop breast cancer than those who didn’t use hair dye.
Little to no increase in breast cancer risk was found for semi-permanent or temporary dye use, though an association with nonprofessional application of semi-permanent dye to others was noted. This risk increased with frequency of use.
Straightener use in the year before the study was associated with an 18% higher breast cancer risk, while a 31% higher breast cancer risk was found for women who used straighteners at least every five to eight weeks.
This risk did not vary by ethnicity, but the use of straighteners is much higher in Black women (74.1%) than in White women (3%).
A 2021 analysis that included 210,319 participants provided significant evidence to support that chemicals in permanent hair dyes increase the risk of breast cancer, but it did not find significant evidence of an increased cancer risk associated with the use of hair straighteners.
What Isn’t Known
Determining if the associations found between hair dye and cancer represent a risk—and to what degree—is difficult to determine with current research.
In addition to inconsistent findings between studies, the studies themselves often have limitations that could influence the results, such as:
Other possible contributing factors, like smoking or oral contraceptive use in participants Recall bias or errors when asking about hair dye use Not being able to evaluate the formulations of the products used by the participants Differences between hair dyes Changes in ingredients based on time period manufactured and used Samples of participants that are not sufficiently diverse (many studies focus primarily on White women)
Effect on Black Women
The 2019 study on the association between hair dye, straighteners, and breast cancer found that the use of hair dye disproportionately increased the risk of breast cancer for Black women than for White women, particularly with regular use.
Toxicological assessments have found higher concentrations of estrogen and endocrine-disrupting compounds in hair products that are marketed toward Black women, which may contribute to the increased risk levels.
Research on hair dye and cancer risk has focused primarily on White women, making the results of most studies not applicable to Black women. Further, there is a comparative lack of research on cancer risk associated with hair straighteners, which are primarily used by Black women. This makes it difficult for Black women to accurately make risk assessment decisions about hair products.
More research is needed into how these products impact the cancer risks for Black women.
Safety for Salon Professionals
To prevent exposure to formaldehyde, it’s best to use products that do not list formaldehyde, formalin, methylene glycol, or any of the other names associated with formaldehyde.
If these products are used, salon owners (and other employers) must comply with OSHA’s standards for formaldehyde and hazard communication.
If you are a hair professional using products that may contain formaldehyde or other potentially hazardous substances, take steps to protect yourself, such as:
Read and make sure you understand the ingredient and warning information on each product’s label Read the Material Safety Data Sheet (MSDS) for each product, and learn about their hazards Work in a well-ventilated area using ventilation systems, such as fans or windows Use personal protective equipment (PPE) as necessary, such as gloves, a face shield, goggles, and chemical-resistant aprons Know where to find first aid equipment, such as eye washing and skin washing, in your workplace Learn how to safely clean up product spills Get medical attention (and tell your employer) if you know you have had direct exposure to large amounts of formaldehyde (such as a spill), or if you develop symptoms of formaldehyde exposure
Safety With At-Home Dyes
Some safety tips for dyeing your hair at home include:
Read and follow the directions that come with the product, including “caution” and “warning” statements Do a “patch test” (a small amount applied to the skin to test for an allergic reaction) every time you dye your hair, even if you have used the product before (allergies can develop with repeated exposure) Apply the dye in a well-ventilated area Wear gloves while applying the dye Never mix different hair dye products If you have bleached, relaxed, or permed your hair, wait at least 14 days before dyeing your hair Don’t use hair dye or relaxer if your scalp is damaged, sunburned, or otherwise irritated Never apply to eyelashes or eyebrows, and keep the hair dye away from your eyes Keep track of time and don’t leave the product on longer than the directions indicate Thoroughly rinse your hair and scalp with water after dyeing Keep hair dye products out of reach of children
If you encounter a problem, talk to your healthcare provider about exposure risk.
Non-Toxic Hair Dye
Vegetable-based hair dyes are available, which may be an option for people who are concerned about the safety of traditional hair dyes. The color change is typically less drastic and fades sooner than with permanent dyes.
Some may include ingredients found in permanent dyes, so read the label before use.
Summary
Some studies show a link between some types of cancers and the use of hair dyes and/or straighteners, though other studies have seen conflicting results. Studies on this subject often have limitations, such as participant samples that include mostly White women. Research also shows an increased risk of cancer in Black women, especially with regular hair dye use.
Safety measures should be taken when using hair dye and straighteners, such as avoiding products with formaldehyde as much as possible, wearing gloves, and applying in a well-ventilated area.
A Word From Verywell
Dyeing your hair is a personal choice. However, it’s important to read the safety information and use your judgment in terms of risk assessment. If you’re unsure, talk to a healthcare provider about any concerns you may have.
