What’s the Deal with Keratin Treatments?

Isabel Platt and Meg Thornberry, National Center for Health Research

Have you ever gotten a keratin treatment? A Brazilian Blowout? Maybe you’ve heard that they make hair silky smooth and relaxed and cost about $400. Or maybe you’ve heard that they can cause cancer. Are the risks greater than the benefits?

What is a Keratin Treatment?

Keratin is a protein found in the hair, nails, and skin. Keratin affects your hair texture and whether it is straight, wavy, or curly. Using chemicals to change the molecules in coiled or curly hair to make it straight or wavy is known as relaxing the hair. In a keratin treatment, cream containing formaldehyde (or another chemical that releases formaldehyde) is brushed into the hair, which is then blown dry and flat-ironed. The combination of formaldehyde, heat, and compression cause straight keratin in the cream to bind to the keratin in the hair, making curly or wavy hair more relaxed.[1]

Why is Formaldehyde a Problem?

Formaldehyde is a colorless, strong-smelling gas that causes health problems when inhaled, sprayed into the eyes, or absorbed through the skin. It can irritate the eyes, nose, and throat, cause coughing and wheezing, and trigger a severe allergic reaction of the skin, eyes, and respiratory tract.[2] Some people have also reported that it caused headaches, dizziness, nausea, chest pains, vomiting, and rashes.[3]  Repeated exposure at high levels has been linked to various cancers[4], especially leukemia.[5] Formaldehyde is released at highly concentrated levels when it is heated, so stylists that perform keratin treatments and customers that repeatedly get them are at a greatest risk for these health problems.[4]

Which Products and Ingredients are Dangerous?

The national Occupational Safety & Health Administration (OSHA) and the New York State Department of Health list the following as some of the companies that sell one or more products that contain formaldehyde: Brazilian Blowout, Badiveu Brazilian, Coppola Keratin, Global Keratin, IBS Beauty, Kera Green, Marcia Teixeira, Pro-Collagen RX and QOD Gold. [7] See the full list of products here. Many of these products have been banned in the E.U. and Canada due to their health risks.[8] All of these treatments contain either formaldehyde or another chemical that releases formaldehyde when heated. The following chemicals are all considered formaldehyde by OSHA: methylene glycol, formalin, methylene oxide, paraform, formic aldehyde, methanal, oxomethane, oxymethylene, or CAS Number 50-00-0.[6] There are also other hair products, such as conditioners and hair sprays, that contain keratin but do not contain any form of formaldehyde, and do not require heat activation. They just leave keratin on the outside of your hair, rather than binding the molecules together. So, it’s best to read the ingredients label before taking any product home, to make sure that you aren’t exposing yourself to formaldehyde, whether it’s listed as formaldehyde, or by one of these other names.

It’s important to know that Keratin is not the only hair straightener that is dangerous.  A 2022 study indicated a possible link between the use ofchemical hair straighteners in general and uterine cancer. Researchers found women who applied chemical straightening products on their hair at least four or more times a year were more than twice as likely to develop uterine cancer compared to those that did not. and that Black women were at higher risk.  [9]

Following the 2022 NIH study, a lawsuit was filed again L’Oreal and other beauty companies for selling chemical hair straightening products [10].

Isn’t a Brazilian Blowout “Formaldehyde-Free”? No!

Brazilian Blowout is one of the most common brands of keratin treatments. As a result of the 2010 controversy over formaldehyde in keratin treatments, Brazilian Blowout created a formula that they advertised as “formaldehyde-free.” While there is no formaldehyde listed in the ingredients, the main chemical used is methylene glycol, which releases formaldehyde when it is heated during the treatment process. Because of this, the FDA issued a warning letter to Brazilian Blowout in 2011 saying that the product is “misbranded” because the “formaldehyde-free” label is false or misleading.[11] Brazilian Blowout is actually one of the most dangerous treatments because almost 12% of the product is basically formaldehyde hiding under another name, and contains three times as much formaldehyde as most other keratin treatments.[6] Five other keratin treatments labeled “formaldehyde-free” were also found to contain formaldehyde levels up to five times the recommended amount.[12]

In response to the FDA’s letter, Brazilian Blowout changed the labeling on their original formula to warn consumers about health risks, and created an alternative product called Brazilian Blowout ZERO+, which does not contain any formaldehyde. But according to a company representative, the new product does not leave the hair as smooth as the original.[1]

Risks to Stylists and Customers

Because stylists are at greatest risk for formaldehyde exposure, OSHA issued a set of guidelines to protect their health. If workers have been exposed to more than a specified amount of formaldehyde, their health must be monitored and they must be reassigned to a job with significantly less exposure. The salon is required to install ventilation systems, use lower heat settings on blow dryers, and monitor formaldehyde levels at all times using a Consumer Sampling and Analysis Kit.[3] Other workers should also be trained annually to safely handle chemicals and be provided personal protective equipment, including gloves, aprons, and eyewash stations.[2]

If you want to protect workers from the health risks of formaldehyde, don’t get a keratin treatment. If you are thinking of getting regular keratin treatments anyway (Brazilian Blowout recommends getting treatments every 12 weeks), remember that you also put yourself at greater risk for irritation, for allergic reactions, and even for cancer. If you want to straighten your hair, remember than using a flat iron releases water vapor, which is much safer for your health. Of course, any form of straightening will damage hair, and should be used sparingly, alternating with protective hair styles that don’t require altering hair’s natural texture, such as braids or gentle twists. These will give your hair (as well as your skin and sinuses) a break from harsh chemicals and heating elements.

We agree with other experts who say that the FDA should prohibit the use of formaldehyde in hair straightening products.  The FDA started to do so in 2016, but for reasons that are not clear, that decision was blocked.[13].  We also urge the Federal Trade Commission to crack down on false advertising by products labeled as “formaldehyde-free.”


All articles on our website have been approved by Dr. Diana Zuckerman and other senior staff.

  1. Environmental Working Group. Best options for straight hair, Hair Straighteners. ewg.org. http://www.ewg.org/hair-straighteners/our-report/how-to-get-straight-hair-whats-the-best-option/. April 2011.
  2. Occupational Safety and Health Administration. OSHA Fact Sheet: Formaldehyde. Osha.gov. https://www.osha.gov/OshDoc/data_General_Facts/formaldehyde-factsheet.pdf. April 2011.
  3. S. Food & Drug Administration. Hair-Smoothing Products That Release Formaldehyde When Heated. Fda.gov. https://www.fda.gov/cosmetics/cosmetic-products/hair-smoothing-products-release-formaldehyde-when-heated#:~:text=A%20hair%20straightening%20or%20smoothing,the%20air%20as%20a%20gas. Updated August 24, 2020.
  4. National Cancer Institute. Formaldehyde and Cancer Risk. Cancer.gov. https://www.cancer.gov/about-cancer/causes-prevention/risk/substances/formaldehyde/formaldehyde-fact-sheet#what-has-been-done-to-protect-workers-from-formaldehyde Updated June 10, 2011.
  5. Schwilk E, et. al. Formaldehyde and leukemia: an updated meta-analysis and evaluation of bias. Journal of Occupational and Environmental Medicine. 2010;52(9):878-886. https://journals.lww.com/joem/Abstract/2010/09000/Formaldehyde_and_Leukemia__An_Updated.5.aspx.
  6. Environmental Working Group. Brands that hide formaldehyde. ewg.org. http://www.ewg.org/hair-straighteners/our-report/hair-straighteners-that-hide-formaldehyde/. April 2011.
  7. New York State Department of Health. Consumer Health Alert: Hair Straightening Products and Formaldehyde. health.ny.gov. https://www.health.ny.gov/environmental/chemicals/formaldehyde/consumer.htm#:~:text=You%20may%20continue%20to%20be,treatments%20of%20BKT%20hair%20straighteners. Updated May, 2017.
  8. Women’s Voices for the Earth. Hair Straightening Products Containing Formaldehyde. womensvoices.org. https://www.womensvoices.org/safe-salons/brazilian-blowout/hair-straightening-products-containing-formaldehyde/. Updated January, 2018.
  9. National Institute of Health. Hair straightening chemicals are associated with higher uterine cancer risk. https://www.nih.gov/news-events/news-releases/hair-straightening-chemicals-associated-higher-uterine-cancer-risk. 17 October 2022.
  10. Melillo, Gianna. Lawsuit against L’Oreal, beauty companies alleges hair straightening products cause uterine cancer. The Hill. October 25th, 2022. https://thehill.com/changing-america/well-being/prevention-cures/3703073-lawsuit-against-loreal-beauty-companies-alleges-hair-straightening-products-cause-uterine-cancer/
  11. S. Food and Drug Administration. Warning Letter: Brazilian Blowout 8/22/11. College Park, MD: U.S. Food and Drug Administration; August 22, 2011. https://www.fdalabelcompliance.com/letters/ucm270809.
  12. Maneli MH, Smith P, Khumalo, NP. Elevated formaldehyde concentration in “Brazilian keratin type” hair-straightening products: A cross-sectional study. Journal of the American Academy of Dermatology. 2013;70(2):276-280. https://www.jaad.org/article/S0190-9622(13)01135-3/fulltext#back-bib7
  13. Rabin RC. The FDA Wanted to Ban Some Hair Straighteners. It Never Happened. The New York Times. October 21, 2020. https://www.nytimes.com/2020/10/21/health/brazilian-blowout-formaldehyde-fda.html.