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Straight hair goes in and out of style. But for some people, there’s nothing quite like the feel of flipping a long, sleek strand of hair over the shoulder or the look of a shiny, perfectly straight ponytail.

If you have unruly hair, unmanageable frizz, or noncommittal waves, you may spend half an hour each morning straightening your hair.

What if it was possible to wake up with straight hair every day?

With the Japanese hair straightening technique, you may be able to do just that.

Japanese hair straightening, also known as thermal reconditioning, is a hair treatment that leaves your locks looking perfectly slick and wave-free for 6 months or longer.

Neil Moodie, one of the UK’s top hair stylists, says the treatment uses a cysteine-based chemical solution to break the bonds and reconfigure the natural structure of the hair from the inside out.

The process dates back to the 1990s, when Japanese hair expert Yuko Yamashita patented the method. Since then, it’s become a popular method for dealing with all types of wavy, curly, frizzy, or generally unruly hair all over the world.

According to the team at Jeju Hair in London, “It’s been popular in countries such as Japan and South Korea for more than 20 years. It’s also now popular in many other countries. We have clients traveling from around the UK and abroad to have [this treatment] with us.”

If you’ve already done a little research on permanent and semi-permanent hair straightening treatments, you may have come across some other names for Japanese hair straightening.

Japanese hair straightening is also known as

  • acid perm
  • thermal straightening or thermal reconditioning
  • chemical hair straightening
  • yuko
  • liscio
  • shiseido
  • cysteine hair treatment
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Getting any kind of permanent treatment may initially seem a little daunting, so it’s always important to fully understand the process.

With Japanese hair straightening, a chemical solution containing cysteine is used to “change the structure of the hair permanently,” Moodie explains.

The process, from start to finish

  1. The cysteine solution is applied to the hair.
  2. The solution is left on the hair for 20 minutes. During this time, a chemical process disables bonds in the hair.
  3. The product is washed out.
  4. The hair is prepped with conditioning treatments that will keep it hydrated and strong throughout the process.
  5. Small sections of hair are passed through a hair straightener at 180°F (82°C) or lower for damaged hair.
  6. After the hair is fully ironed straight, then it needs to be neutralized with another solution. This takes approximately 10 minutes.
  7. The neutralizer is rinsed out.
  8. The hair is blow-dried without the use of styling brushes.
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As with any treatment, it’s important you take good care of your hair after the treatment to ensure you get the best results and don’t damage your hair.

In the first 72 hours

In the first 3 days after getting your treatment, your hair will need some special care.

  • For 3 days, keep your hair completely dry.
  • Avoid showers, rain, or even sweat.
  • Avoid any hair products such as oils, gels, or dry shampoo.
  • Try to keep your hair as straight as possible by leaving it down and keeping it untucked from the ears.

After 72 hours

After the first 3 days, the treatment should set, and, for the most part, you’ll be able to go back to your normal hair routine.

A few exceptions include:

  • Avoid chlorinated water for a few weeks.
  • Avoid too much sun exposure.
  • Avoid sulfur-based shampoos. If possible, use products that are designed for chemically straightened hair.

Check with your hair specialist about which hair products are best to use.


  • You’ll spend less time getting ready each morning.
  • You won’t have to worry about your hair getting wet during the day: it will naturally air dry straight!
  • Your hair may feel and look healthier in the long run, as you won’t need to use heat styling tools on your hair every day.
  • You’ll still be able to style your hair using a curling iron if you choose to.


  • The hair may appear thinner.
  • The procedure can be fairly expensive, costing several hundred dollars.
  • Even though the procedure needs to be touched up, your hair will never have the same body or shape after your first session.
  • The procedure can damage your hair if you have an inexperienced stylist. Be sure to do a strand test before committing to the procedure on a full head of hair.
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Still got some questions? We’ve got you covered.

How long does it take?

The procedure will probably take around 1 to 1.5 hours. The initial consultation and strand test will also take about an hour.

How long does it last?

The procedure is permanent, but as your hair grows out, the roots will need to be touched up.

Eventually, you’ll be able to grow out all of your straightened hair. Alternatively, you can opt for a touch up around every 6 months to maintain the look.

How much does it cost?

Most salons will charge from around $400 to $800 for a single treatment.

How do you sleep on it?

In the first few days after the treatment, it’s important to keep the hair as straight as possible.

To avoid getting kinks in your hair after the procedure, keep your hair down overnight instead of tying it up.

Try to lie on your back with your hair splayed out on the pillow beneath your head.

Is it bad for your hair?

While the mention of chemicals may sound a little frightening, Japanese hair straightening is generally safe for most people when it’s done correctly.

In the long run, it can even improve hair health because you’ll likely use fewer heat styling products.

Still, there are always risks when using intensive chemical treatments. For some people, straightening may present even more risks.

For instance, if you’ve already had chemical treatments or if your hair’s been colored, you may be more likely to experience hair damage from Japanese hair straightening.

After having the treatment done more than twice, it’s not recommended to get it again.

As stylist Ted Gibson told NY Mag, “In some cases, the hair was melted off. [Clients] were left with fried-out stubs.”

According to a 2015 study, restructuring the hair with a chemical solution fundamentally changes your hair chemistry. This can result in damage.

It’s important to consult your hair stylist about the treatment and give it plenty of thought before diving in.

Can you use hair ties, pins, or clips?

After the initial aftercare period, which usually lasts around 3 days, you can use any kind of hair accessory.

However, for long-lasting results, try to use soft, gentle accessories that don’t cause harsh kinks in the hair.

What happens after the first wash?

Most stylists advise against washing the hair until 3 days after the treatment.

After your first wash, your hair should be straight after being blow dried or air dried.

Where to get it done?

It’s important to find a reputable, licensed salon.

In general, it’s probably smart to begin your hunt for the perfect salon in large cities. Many experienced hair stylists tend to gravitate to pricier, well-known salons in major metro areas, though this isn’t always the case.

Be sure to check reviews and testimonials and, if possible, before and after pictures. And don’t forget to do a strand test first!

Can you do it at home?

No, only trained professionals with the right tools and skills are able to perform the treatment.

Can you undo it?

Japanese hair straightening is a permanent process, so no, you can’t undo the procedure.

Once you’ve chemically straightened the hair, the structure of the hair itself is permanently changed. The only way to regain your old texture and shape is to let the hair grow out.

How do you grow it out?

Unfortunately, if you’re unhappy with the results, waiting is the name of the game.

It may take a year or 2 before your hair fully grows out. Keep getting regular trims to help your hair grow out more quickly.

A “relaxer” is another permanent hair straightening treatment. Like a Japanese treatment, a relaxer works by changing the hair’s internal structure.

The process involves using a relaxer formula, which usually contains sodium. This treatment is usually recommended for people with extremely kinky hair, while the Japanese treatment is recommended for those with softer curls or waves.

A keratin treatment, also known as a Brazilian blowout, is a semi-permanent hair straightening treatment.

Unlike the Japanese hair treatment, keratin treatments do not alter the internal bonds of the hair. Instead, they smooth out hair from the outside.

This treatment only lasts for around 2 to 4 months. It’s also slightly less effective, as it doesn’t alter the hair from the inside out.

While a Japanese hair straightening treatment will leave you with ultra-straight tresses, a keratin treatment will reduce frizz and slightly straighten curly or wavy hair.

Hair rebonding is also known as chemical straightening. It’s similar to Japanese straightening in that it breaks apart the bonds of the hair.

One main difference is that it typically uses chemicals such as:

  • formaldehyde
  • aldehyde
  • methylene glycol
  • methanal

A large 2019 study found those who received chemical straightening every 5 to 8 weeks to be more likely to develop breast cancer.

The study also noted that formaldehyde is a known carcinogen, which means it’s capable of causing cancer in living tissue.

With a consultation and an experienced stylist, the Japanese hair straightening treatment shouldn’t pose any risks.

However, if the wrong candidates get the treatment or an inexperienced hair stylist performs the treatment, things can go wrong.

As one stylist at Jeju Hair explains, “The main risk is damaging or breaking the hair if the stylist is not experienced and leaves the chemicals on the hair for too long. The stylist should be able to judge when the chemical has been on long enough to be effective — very thick or curly hair can need longer times — but also when it must be rinsed out before it damages the hair.”

Anecdotally, some people feel strongly about Japanese hair straightening.

One member of the Wedding Bee forum wrote, “Do NOT get the Japanese hair straightening method. It fried my hair. 3 years later and it’s just starting to recover. What a nightmare.”

Writer Zainab Damji had a bad experience when her hair became extremely sensitive.

“Coloring it or applying any sort of heat will literally frazzle it to a crisp,” Damji wrote in Grazia. “I know from experience. My hair looked and felt awful. Not only was it falling out, but I was getting split ends faster than ever, forcing me to chop it all off. Bye-bye long, luscious hair.”

Of course, this isn’t the case for everyone.

To avoid any unwanted results, make sure you follow best practices if you choose to use this treatment.

What to know before you go

  • Find a reliable stylist and salon.
  • Do a strand test.
  • Be honest about your hair type and procedure history.
  • Do not get more than one or two chemical treatments on the same hair.
  • Do not get the treatment on colored hair.
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Japanese hair straightening can be a great option for some people who want to manage their frizzy or curly hair.

However, the procedure involves strong chemicals, so make sure you do your research and prep for careful aftercare before diving in.

Make sure you find a reputable, experienced professional to provide the treatment, and follow after procedures closely.

Meg Walters is a writer and actor from London. She is interested in exploring topics such as fitness, meditation, and healthy lifestyles in her writing. In her spare time, she enjoys reading, yoga, and the occasional glass of wine.