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What Is Japanese Hair Straightening?

Maffew is a hairdresser, marketer, and dabbler in many things who enjoys sharing knowledge about the science of hair coloring and hair care.


Japanese hair straightening is a method of permanent hair straightening that has become popular around the world in recent years. The treatment can give you beautiful, flawlessly straight hair, but is it the right choice for you?

This article will tell you everything you need to know about this popular straightening treatment, including how it differs from the other available options and how it is performed.

What Is It?

Curly and wavy hair look that way because disulfide bonds cause the structure of your hair to curve back towards itself. These kinds of bonds are present even in naturally straight hair, where they are also responsible for much of your hair's strength. It's the amount and position of bonds, rather than presence alone, that determines its texture.

Also known as thermal reconditioning because of the way it is applied, Japanese straightening uses ammonium thioglycolate to break these bonds so that they can be reset in a way that creates straightened hair.


Benefits and Drawbacks

Japanese hair straightening works in a very similar way to relaxers, but unlike traditional hair relaxers, it uses a different active ingredient to straighten your hair. This makes the treatment, milder, safer, and much less damaging for your hair.

The major benefits to this kind of straightening include:

  • Less damage
  • Perfectly straight hair that doesn't curl in response to water or humidity
  • A smooth texture, making your hair easier to style
  • Permanent results that don't wear off or wash out over time
  • Can usually still be performed on dyed or lightened hair


Compared to a relaxer, Japanese hair straightening only mildly damages your hair and you can generally still apply the treatment even if your hair has been colored in the past. Of course, a proper assessment is necessary before application to ensure your hair is in good enough condition for this.

You can also still dye your hair after straightening it, as long as you aren't too aggressive with the number of color changes you want to make. Regular relaxers multiply the damage of any dye that is applied afterward. Japanese straightening does this too, but only to an extent slightly higher than normal, making it a better choice if you color your hair.

Your hair will maintain incredible smoothness and a sleek, straight finish permanently following the procedure. Unlike a keratin treatment, Japanese hair straightening doesn't diminish over time. Previously straightened hair will remain that way permanently while new regrowth will have to be treated again after several weeks to maintain the effect as your hair grows.

Overall, this kind of straightening is a great option to keep a sleek hairstyle with minimal damage while retaining the ability to change your hair color. If you want to wear curls or waves sometimes, you can still do this temporarily using a straightener or curling rod.


As with any other straightening treatment, there are also drawbacks to its use that you need to be aware of before deciding if the procedure is right for you. While you can dye your hair before and after straightening, the amount of damage is compounded slightly compared to natural hair, and the treatment itself adds a small amount of damage to your hair because it breaks bonds.

Japanese straightening has drawbacks of being:

  • Somewhat damaging
  • Very costly
  • A long application time
  • Difficult procedure requiring a salon visit
  • Unsuitable for very damaged hair

Unless you're very experienced in the use of relaxers and can ensure that you use them properly, this kind of straightening treatment shouldn't be applied at home and this, combined with the long time required to perform the treatment, makes it very costly.



Thermal reconditioning costs a lot. Salons charge several hundred dollars for the treatment, and this can vary based on the amount of experience your hairdresser has with the treatment and other factors like your hair length and thickness.

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Most of this exorbitant cost is the result of the difficulty and time involved because while you can technically apply it at home at a fraction of the cost, you should only do this if you have extensive experience with relaxers. Used incorrectly, the treatment can damage your hair severely and cause chemical burns or damage to your eyes. When in doubt, avoid use.

In the hands of a professional, however, it is a very mild and safe way to straighten your hair, albeit pricey.

Japanese Straightening vs. Keratin Treatments vs. Relaxers

Of the three available options to chemically straighten hair, thermal reconditioning is the best option for hair that is either natural or minimally dyed.

If you dye your hair extensively or have severely damaged hair, a keratin treatment is a much better option that is safe to use on your damaged hair. In fact, it reverses the damage. The drawback is that it only lasts a few months and requires a lot more maintenance.

Traditional relaxers should generally be avoided in most cases because the Japanese straightening method supersedes them. You can use the table below to gain a better understanding of how all these treatments compare.

Thermal ReconditioningKeratin TreatmentRelaxer

Mild damage


Very damaging

Permanent results

Semi-permanent (2–3 months)

Permanent results

Okay on colored hair

Best option for colored hair

Avoid on colored hair

Very expensive in salon

Can be expensive in salon


Low maintenance

Higher maintenance

Low maintenance

Longest application time

Long application time

Shorter application time


How It Is Performed

After assessing your hair condition, your hair will be gently shampooed and then given a pre-treatment to improve the results and ensure any potential problems like previous damage are addressed first. Stylists highly experienced in Japanese hair straightening will look at many sections of your hair to get a good idea of how each area will react to the product and adjust their application based on what they notice.

Treatment Application

Once your hair has been pre-treated, the thermal reconditioning treatment will be applied quickly and evenly. Application speed is critical to results because the hair it is applied to first will be exposed for longer, increasing the risk of damage. The treatment is left in your hair for a period of time after this, depending on how curly and coarse your hair is and the bonds will start to be broken.

This alone isn't enough to get your hair straight through, as these bonds will gradually reform. To prevent them from reforming in the wrong way, your hair will be rinsed and then blow-dried and straightened meticulously, similar to how a keratin treatment is applied.

The blow-drying and iron-straightening part of the procedure is where the bulk of the time and cost occurs because the way it is handled will directly influence the final result. Your hair must be dried smooth in the direction of growth, then every section needs to be straightened perfectly to lock in the precise position for new bonds to form.

These new bonds will make your hair permanently straight if applied correctly and your hair will then be neutralized for a period of time using hydrogen peroxide to set them in place. Following this, drying and flat-iron straightening occur yet again, and you will need to maintain your hair in this straightened style for several days before washing, which is again, a lot like the method for using a keratin treatment.

Your hair will be straightened with a flat iron twice during treatment to position and set the new bonds in place.

Your hair will be straightened with a flat iron twice during treatment to position and set the new bonds in place.

Aftercare and Maintenance

Hair that has been treated with Japanese hair straightening needs to be kept straight and smooth for a period of up to three days following the treatment, but there isn't any specific hair care regime required after that. This is different from a keratin treatment where you need to use specialized shampoo and conditioner and avoid certain things like saltwater to extend how long it lasts.

With that said, there are definite things you can do to keep your hair in good condition and this will help to make your new straightened hair look even better. Aftercare can include:

  • Protein treatments to reverse the damage
  • Conditioning treatments to make the hair feel silkier and alleviate dryness
  • Hair products like serums to make your hair glossy

You can style your hair in any way you want, including curls or waves using a curling rod or flat iron if you would like to bring back some curl temporarily, but you should always use a heat-protectant spray before using any form of heat-styling to prevent further damage.

You do need to avoid extensive use of dyes or bleach, however. Hair that has been smoothed with Japanese hair straightening can be dyed, but you should keep this to a minimum and only if your hair is still in good condition. Always assess the health of your hair before applying any further chemical treatments.


Japanese hair straightening is the best way to get permanently straight hair with minimal damage, but it's not for everyone. The treatment is costly and time-consuming, making it one of the most extreme processes you can put your hair through. If you've decided to try it though, you can rest assured that it will give you smoother hair than you've ever imagined you could have.

Have a question about permanent straightening or a particular treatment? Leave a comment to share your insight with other readers.

© 2020 Maffew James

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