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Common Side Effects of Chemical Hair Straightening

The most common side effects of chemical hair straighteners and relaxers include hair damage and skin irritation. However, the ingredients in many hair relaxers, including keratin/Brazilian straighteners and Japanese heat straighteners, are associated with serious hazards to human health.

Widely used and potentially harmful compounds found in many chemical hair straightening products include lye (sodium hydroxide), formaldehyde, cyclosiloxanes, parabens, diethanolamine, phthalates, benzophenone-3 and triclosan. The U.N. Environment Programme classified types of parabens as endocrine disruptors and possible endocrine disruptors, for example.

Side effects associated with these compounds include:
  • Adverse developmental effects to embryos, fetuses, babies and children
  • Allergic sensitization (becoming sensitive to an allergen)
  • Asthma attacks and other respiratory complications
  • Burns of the eyes, lungs, nose and skin
  • Endometriosis
  • Hair loss (often temporarily)
  • Impaired fertility or infertility
  • Impaired immune and nervous system functions
  • Potential increased risk of cancer – including breast, skin and uterine cancer
  • Skin conditions and skin rashes
  • Vision impairment and vision loss

The World Health Organization’s International Agency for Research on Cancer classifies formaldehyde as a carcinogen. IARC’s report stated, “There is sufficient evidence in humans for the carcinogenicity of formaldehyde. Formaldehyde causes cancer of the nasopharynx and leukemia. Also, a positive association has been observed between exposure to formaldehyde and sinonasal cancer.”

Side effects of harmful products can not only impact consumers who have them applied to their hair regularly, but can also impact salon staff who are exposed to these ingredients daily.

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Long-Term Effects of Chemical Hair Straighteners

A 2022 study from the National Institutes of Health states that women who used chemical straightening products were at a higher risk for uterine cancer than women who did not. In fact, researchers found that women who reported use of hair straightening products more than four times in the previous year were more than twice as likely to develop uterine cancer than those who did not use chemical hair relaxers.

Dr. Alexandra White, head of the NIEHS Environment and Cancer Epidemiology group and lead author on the new study, noted: “This doubling rate is concerning. However, it is important to put this information into context – uterine cancer is a relatively rare type of cancer.”

Additionally, NIH researchers previously reported on the association between hair straightening products and cancer, finding increased risk for both breast and ovarian cancers. Women who used hair straighteners at least every five to eight weeks were about 30% more likely to develop breast cancer.

The study’s authors also state that results must be replicated before medical professionals can make more firm medical recommendations around chemical hair straighteners and cancer. Consumers who have developed serious side effects, including uterine cancer, after use of hair relaxers, however, have begun filing chemical hair straightener lawsuits seeking compensation for medical expenses, as well as pain and suffering.

How to Avoid Side Effects of Hair Straightening

Although the effectiveness of non-chemical hair straightening methods can be debated, it is typically safe to experiment with them. Flat irons are safe but can damage hair if overused.

Other methods include:
  • Wrapping hair.
  • Using large rollers.
  • Blowing dry with cold air.
  • Applying hair masks or essential oils.

Using a natural product such as coconut oil may help to relax the cuticle and eliminate frizz.

Is Chemical Hair Straightening Safe?

If you are a consumer or a hair stylist who uses or works with hair straightening treatments, you are at risk for exposure to formaldehyde, a known asthmagen and carcinogen. Parabens, another chemical found in hair straighteners, are linked to reproductive problems.

In many cases, manufacturer claims of formaldehyde-free products have been proven false. Formaldehyde-free hair straighteners do not technically contain formaldehyde as an ingredient, but rather they contain other chemicals that release formaldehyde when in contact with the high heat necessary in order for these straightening treatments to work.

Though more studies are required, federal and state governments are concerned about the potential for adverse impacts from many chemicals found in hair straightening products. Studies have proven a link to cancer and other serious health problems.

Please seek the advice of a qualified professional before making decisions about your health or finances.
Last Modified: August 8, 2023

9 Cited Research Articles

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  1. NIH. (2022, October 17). Hair straightening chemicals associated with higher uterine cancer risk. Retrieved from https://www.nih.gov/news-events/news-releases/hair-straightening-chemicals-associated-higher-uterine-cancer-risk
  2. Hatsbach de Paula, J. et. al. (2022, January 17). Effects of chemical straighteners on the hair shaft and scalp. Retrieved from https://www.sciencedirect.com/science/article/pii/S0365059621003147
  3. Godio, M. (2020, July 20). 8 best flat irons, according to hair experts. Retrieved from https://www.nbcnews.com/select/shopping/best-flat-irons-hair-straighteners-ncna1234372
  4. NIH. (2019, December 4). Permanent hair dye and straighteners may increase breast cancer risk. Retrieved from https://www.nih.gov/news-events/news-releases/permanent-hair-dye-straighteners-may-increase-breast-cancer-risk
  5. IARC. (2018, June). Formaldehyde. Retrieved from https://monographs.iarc.who.int/wp-content/uploads/2018/06/mono100F-29.pdf
  6. EcoWatch. (2014, March 18). 33 Toxic Hair Straighteners Under International Recall Still Sold in U.S. Retrieved from https://www.ecowatch.com/33-toxic-hair-straighteners-under-international-recall-still-sold-in-u-1881878913.html
  7. Skwiot, S. (2014, February 3). How to Straighten Your Hair With a Blow Dryer in 7 Simple Steps. Retrieved from https://cafemom.com/lifestyle/167415-how_to_straighten_your_hair
  8. Pechter, E. (2011, December 1). Hair straightening with health risks. Retrieved from https://www.cdc.gov/niosh/nioshtic-2/20042624.html
  9. Department of Toxic Substances Control of California. (n.d.). Chemicals in Hair Straightening Products. Retrieved from https://dtsc.ca.gov/scp/chemicals-in-hair-straightening-products/