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Permanent Hair Straightening: Risks, Side Effects and What To Know

Permanent hair straightening offers a long-term style change for people with curls, though you should consider health risks such as formaldehyde exposure and uterine cancer. Learn more about the main types of treatment, other risks and heat-free alternatives to try.

Last Modified: October 5, 2023
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Woman having a hair product applied.
Key takeaways:
  • Women who regularly use hair-straightening chemical products face double the risk of developing uterine cancer before the age of 70, compared to those who don’t.
  • All hair straightening chemicals carry the risk of exposure to carcinogenic gases. This occurs when the chemicals evaporate and are inhaled.
  • Black women are disproportionately impacted by health risks from chemical hair straightening because they use the products more often than any other segment of the U.S. population.

Types of Permanent Hair Straightening

Table of the four methods of permanent hair straightening

People who have naturally curly or textured hair may choose to undergo chemical processes to permanently straighten their hair. Some may opt to go this route for an easier daily hair routine, because they simply like the look or perhaps as a result of societal pressures based on Eurocentric beauty standards.

Regardless of the reasons, it’s a big decision to permanently alter the natural structure of your hair. There are several methods that can provide the long-term effect of straightened hair, but each process carries unique health risks.

1. Keratin Straightening Treatment

“A keratin treatment is considered to be the safest way to permanently straighten hair because it does not rely on harsh chemicals as relaxers and permanent waves do.”

Also known as a “Brazilian blowout,” keratin straightening treatments offer a semipermanent result that can both smooth and increase the shine in your hair. Keratin is a structural protein that is important for strong hair and helps reduce breakage and frizz.

How it works: A stylist applies a keratin-based product that includes a formaldehyde derivative to your hair. The chemical solution temporarily breaks down the structural bonds in each hair strand and then reseals them into a straighter structure. The stylist will then add heat by blow-drying the hair and sealing it with a flat iron.

How long is the appointment? The entire treatment can take two to four hours, depending on your hair length and type.

How long does it last? Results from a keratin straightening treatment typically last between three and six months.

  • Works well on most hair types.
  • Reduces hair frizz.
  • Reduces the development of split ends.
  • Adds shine.
  • Seals in hair color and makes it last longer.
  • Fades out over time.
  • Should avoid water and ponytails for the first three days post-treatment.
  • Not recommended for people with damaged or super-fine hair due to additional heat damage risks.
  • May only smooth hair instead of straightening it.
  • Potential exposure risks to formaldehyde, even with products labeled formaldehyde-free.
  • Once it washes out, your hair may not return to its original state.
  • Carries the risk of inhalation exposure to carcinogenic gases.

Cost: The average cost range of a keratin treatment is approximately $80 to $400.

2. Japanese Thermal Straightening

“The safest way to straighten hair is through Japanese thermal. It is also called an acid perm and can last up to six months. People prefer this instead of keratin straightening, which only lasts for three months.”

Sometimes referred to as thermal reconditioning or a straight perm, the Japanese thermal straightening treatment was developed in Japan in the 1990s. Although the results may look the same to some people, it’s considered the more intense option compared to keratin straightening or hair rebonding. The process is basically a blend between traditional hair relaxers and keratin treatments.

How it works: A trained professional applies a chemical solution to your hair, breaking its bonds in order to soften the texture and straighten out the structure. After washing out the chemicals, they’ll apply heat via a blow-dryer and flat iron to seal in the smoothing effect. The stylist will then apply a second solution of a keratin neutralizer to help bring your hair’s pH levels back up. A second wash and another blow-dry and flat iron finish up the process.

How long is the appointment? The entire treatment can take two to four hours, depending on your hair length and type.

How long does it last? Results from Japanese thermal straightening typically last up to six months.

  • Adds shine.
  • Creates pin-straight hair.
  • Will not wash out over time.
  • Reduces hair frizz.
  • Uses a cystine-based solution and does not carry the risk of formaldehyde exposure.
  • No option to undo it if you don’t like the results.
  • Requires touch-ups approximately every eight to 10 months.
  • Should avoid water and ponytails for the first three days post-treatment.
  • Can severely increase the damage to colored or other previously chemically processed hair.
  • Not right for everyone, depending on specific hair type.
  • Highest cost.
  • Although reduced compared to other methods, still carries the risk of inhalation exposure to carcinogenic chemicals.

Cost: The average cost range for Japanese thermal straightening is approximately $400 to $800.

3. Hair Rebonding

Hair rebonding is a chemical process perceived by some to be a middle ground between a keratin treatment and Japanese thermal straightening. Like both of those treatments, it can help increase your hair’s shine factor and create a more low-maintenance hairstyle with a smooth finish. The main differentiator is that hair rebonding chemicals do not incorporate formaldehyde.

How it works: A professional stylist will use a chemical cream that permanently alters the structure of your hair. It works by breaking down the disulfide bonds between amino acids and then rebuilding them with a newly straightened permanent structure.

How long is the appointment? The entire hair rebonding treatment can take anywhere from three to eight hours, depending on your hair length and type.

How long does it last? Results from a hair rebonding treatment typically last between six and seven months.

  • Reduces hair frizz.
  • Adds shine.
  • Creates a silky smooth finish to your hair.
  • Fades out over time.
  • Should avoid water for the first three days post-treatment.
  • Potential exposure risks to chemical fumes.
  • Hair may not return to its original state.
  • One of the more costly and time-consuming options available.
  • Often performed using formaldehyde or aldehyde-including chemicals, adding to exposure risks that include uterine cancer.

Cost: The average cost range for hair rebonding is approximately $200 to $600.

4. Chemical Straightening

Traditional chemical straightening treatments are also commonly referred to as hair relaxers. Their history in the United States can be traced back to the early 1900s.

Hair relaxers play a significant role in the Black community as a result of societal biases against natural hair in both social and workplace settings. In fact, a 2021 study revealed that two out of three Black girls ages 5 to 18 who attend majority-white schools have experienced hair discrimination.

How it works: A stylist applies a lye-based chemical relaxer. The main ingredient is usually sodium hydroxide, which helps break down the bonds in the hair shaft. Once broken, the hair pattern straightens out to achieve a sleek look.

How long is the appointment? The entire treatment can take two to three hours, depending on your hair length and type.

How long does it last? Results from chemical straightening are permanent, but they require touch-ups every six to 12 weeks due to new hair growth.

  • Will not wash out over time.
  • Works well on curly and coily hair.
  • Least expensive option.
  • Can severely increase the damage to colored or other previously chemically processed hair.
  • Requires cutting your hair off if you no longer want straight hair.
  • Requires frequent maintenance every six to 12 weeks.
  • Carries increased risk of inhalation exposure to carcinogenic chemicals compared to other methods.

Cost: The average cost range for chemical hair straightening is approximately $40 to $150.

Health Risks and Other Side Effects

The various methods of permanent hair straightening all have one thing in common: chemicals. Although they don’t incorporate the exact same chemicals, the impact of repeated chemical applications to the hair and scalp can cause risks and side effects that range from simply frustrating to downright dangerous.

Graphic showing the health risks of formaldehyde exposure.

Below are common health risks to be aware of before you undergo permanent hair straightening. It’s important to read and understand these risks carefully for your health and safety.

Common Health Risks

Exposure to formaldehyde — a known carcinogen — and formaldehyde-releasing chemicals that occur during some permanent hair straightening processes is a major health concern for both customers and hair care professionals. Pregnant women in particular need to speak with their stylist before planning a hair straightening treatment because some processes are not recommended for them.

While many products now tout themselves as being formaldehyde-free, the chemicals they do include are often “formaldehyde releasers.” Chemical ingredients such as methanal, methanediol, formalin and methylene glycol all release formaldehyde fumes when they are mixed with water during the hair straightening treatment. Additionally, many chemicals that are listed as formaldehyde-free release other closely related compounds that carry similar risks.

One recent study confirmed that women who had used hair-straightening chemical products in the past 12 months had doubled their risk of developing uterine cancer before the age of 70. Sixty percent of the participants who reported they had used straighteners in the year prior self-identified as Black women. So it’s unsurprising to note that, as uterine cancer rates continue to rise, Black women are disproportionately impacted by these diagnoses.

Additional studies have also tied uterine cancer, uterine fibroids, breast cancer and endometriosis to the chemical exposures experienced during these hair processes. This has led to multiple chemical hair straightener lawsuits across the country. However, so far the litigation centers only on uterine cancer, endometrial cancer and ovarian cancer. Lawyers are waiting for more definitive evidence on other injuries before pursuing litigation on other conditions linked to hair straighteners.

Nia Jones, professional hairstylist at Latest Locks, warns about potential skin damage, either through damage to the scalp, skin irritation or allergic reactions.

“Damage to the scalp can include chemical burns and redness or sensitization of the scalp, which can cause subsequent treatments to become problematic,” she stated.

Other concerning health issues include:
  • Endocrine-disrupting chemicals in these products can lead to a higher rate of hormone-related diseases.
  • Asthma-related chemicals released during the processes have been tied to a higher prevalence of asthma among Black women and children.
  • Several types of alopecia in women of color have also been connected in part to the repeated use of hair relaxers.
Lawsuit Information
Women who used chemical hair straighteners and were diagnosed with cancer are filing lawsuits.
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Potential Negative Side Effects

There are a variety of other potential side effects from chemical hair straightening. Some may be visible in the hair itself, while others may be invisible to the naked eye.

Examples of potential side effects include:
  • Hair breakage or weakness due to damaged hair follicles.
  • Long-term costs for post-straightening hair care products.
  • Loss of your natural curl pattern.
  • Risk of making existing hair damage worse.
  • Once you start, you’ll have to continually go back for regular touch-ups (or cut all your treated hair off and start over).
Graphic showing safe alternatives to achieve straight hair.

Ghanima Abdullah, a cosmetologist with The Right Hairstyles magazine, said, “The main side effect is mental. When a person has curly hair and looks in the mirror after getting permanent straightening, there is such a change that the person might struggle to recognize themselves. There’s always an impression when a person straightens their hair that there’s something to fix, that there’s something wrong with their hair in its natural state, and that it’s not good enough for them or those around them.”

Can I Straighten My Hair Without Heat?

The answer is yes and no. Strategies for straightening hair without heat have a better chance of working for people with fine hair that holds only soft waves. Anyone with other hair types face a bigger challenge in achieving straight hair minus the potentially damaging heat factor.

But it never hurts to try, so test out these methods:
  • Swap in a straightening shampoo and conditioner in place of your regular products.
  • Try using your hair dryer’s cold air setting to give yourself a straight “blowout.”
  • Braid wet hair and let it air dry for no-frizz results.
  • Put your hair up into jumbo rollers overnight to gently stretch out and smooth it while it dries.
  • Mix up an all-natural homemade nourishing hair treatment, like a banana papaya hair mask. The banana’s natural oils and potassium work to soften your hair and support its elasticity. And the papaya’s vitamin A helps improve the hair’s ability to withstand breakage. Print the recipe below.
Recipe for an all-natural hair mask.
Download The Hair Mask Recipe Card

No matter what you choose to do with your hair, it’s important to discuss your options with your hair care professional. They can help clarify the risks and side effects you need to know when deciding if the potential dangers of permanent hair straightening are worth it to you.

Infographic explaining permanent hair straightening.
Please seek the advice of a medical professional before making health care decisions.