Hair to Dye for: Hair Dye Safety Studies & Regulation Overview
Hair dye has been a popular beauty product for decades, with many people using it to change their hair color for fashion or personal preference. However, with recent concerns about the safety of cosmetic products, many people are left wondering if their hair color is the only thing affected.
Hair dyes often contain ingredients that can cause skin irritation, allergic reactions, and other adverse effects. Some people are more sensitive to specific ingredients and can also become increasingly sensitized through repeated exposures. The ingredient, p-phenylenediamine (PPD) has been linked to multiple hair dye allergic reactions. Exposure to other compounds have also been shown to cause development of PPD allergies through a process called cross-sensitization. Cross-sensitization PPD events have been linked to the use of black henna, latex, benzocaine, para-aminosalicylic acid, sulfonamides and para-aminobenzoic acid.
Most of the concern about cancer risk has been with the semi-permanent and permanent dyes which penetrate the hair shaft and cause lasting chemical changes to dye the hair. Certain chemicals used in these types of hair dyes, like aromatic amines, have been shown in various laboratory studies to produce positive genotoxic responses in-vitro. However a definitive link between application of hair dye ingredients and cancer in humans has yet to be established through in-vivo studies.
Everytime someone dyes their hair or has it dyed, residual chemicals from hair dyes can be absorbed in small amounts through the scalp or inhaled from produced fumes. Consequently people who work around hair dyes regularly, like hairdressers or barbers, are exposed to said chemicals very frequently. Assuming that certain hair dye ingredients are carcinogenic, then it could be reasoned that groups of people with higher rates of hair dye exposure would be more predisposed to certain forms of cancer than the average person. Several epidemiological studies of different sizes conducted over the years have helped validate this reasoning and it was found that people regularly exposed to hair dye products through their occupation had significantly higher incidence rates of bladder cancer.
It is important to mention that these groups of people studied may have other underlying characteristics that can influence cancer rates aside from hair dye exposure. For this reason epidemiological studies cannot be used as conclusive proof for carcinogenic properties of hair dye and must have their claims supported by relevant lab research and clinical trials. And in similar studies looking at populations of people who regularly dyed their hair a similar correlative increase in bladder cancer rates was not observed.
While there is no conclusive answer for whether certain hair dyes cause cancer in humans, the abundance of epidemiological evidence and laboratory studies performed over the years have produced enough evidence for future safety studies to be considered necessary.
How is Hair Dye Regulated in the USA?
Like with many cosmetics sold in the USA, hair dye regulation is handled by the FDA. However the scope of regulation for hair dye under the FDA is limited. Individual ingredients included in hair dyes do not need pre-market approval by the FDA and responsibility for the safety of hair dye products and ingredients lies primarily in the hands of cosmetic manufacturers. The FDA can and will take action if hair dye products are found to be harmful or violate established regulations.
There is actual historical precedence for FDA regulation of hair dye ingredients that were considered harmful. In the 1980s the FDA issued a special warning for two prominent ingredients used in coal-tar based hair dye which had shown carcinogenic properties in animal models. Following the FDA warning a massive reformulation effort by the cosmetics industry occurred and the two ingredients in question were no longer used in commercially available hair dye. However, many older hair dye ingredients (some which are still currently used) were excluded from regulation when the FDA was given authority over cosmetic standards in the 1930s.
Statement by Research Agencies
Several national and international research agencies that focus on cancer research have conducted multiple studies on hair dye products and have issued the following statements:
The International Agency for Research on Cancer (IARC) is a part of the World Health Organization (WHO) focused on studying various causes of cancer.The IARC has concluded that workplace exposure as a hairdresser or barber is “probably carcinogenic to humans,” based on the data regarding bladder cancer. But IARC considers personal hair dye use to be “not classifiable as to its carcinogenicity to humans,” based on a lack of evidence from studies in people.
The US National Toxicology Program (NTP) is an interagency program of the National Institutes of Health (NIH), the Centers for Disease Control and Prevention (CDC), and the Food and Drug Administration (FDA). The NTP has not classified the potential of hair dyes to cause cancer. However, it has classified some chemicals that are or were used in hair dyes as “reasonably anticipated to be human carcinogens.”
To minimize the potential risks of hair dye either from allergic reactions or other potential adverse effects hair care professionals and dermatologists recommend the following:
- Performing a patch test with your hair dye to test for any allergic reactions before fully applying
- Avoiding hair dyes that include ingredients such as ammonia, peroxide or aromatic amines
- Avoiding frequent application of hair dye to lower the risk of adsorption or sensitization
- Using hair dye formulated from natural ingredients like vegetable-based dyes or henna as an alternative to permanent or semi-permanent oxidative hair dyes.
Preston, R.J., Skare, J.A., & Aardema, M.J. (2010). A review of biomonitoring studies measuring genotoxicity in humans exposed to hair dyes. Mutagenesis, 25 1, 17-23 .
Cytotoxic and genotoxic effects of two hair dyes used in the formulation of black color – PubMed (nih.gov)
Nohynek GJ, Fautz R, Benech-Kieffer F, Toutain H. Toxicity and human health risk of hair dyes. Food Chem Toxicol. 2004 Apr;42(4):517-43. doi: 10.1016/j.fct.2003.11.003. PMID: 15019177.
Hair Dye Ingredients and Potential Health Risks from Exposure to Hair Dyeing | Chemical Research in Toxicology (acs.org)
Hair Dyes and Cancer Risk | American Cancer Society
Do hair dyes increase cancer risk? – Harvard Health