Does a keratin treatment straighten your hair? Only if it contains formaldehyde

keratin in dyed blonde hair

  • If you apply a keratin treatment that contains formaldehyde, it’ll straighten your hair.
  • Some keratin treatments straighten your hair, and some others don’t.
  • If your idea is to straighten your hair, you can use keratins with formaldehyde.
  • On the other hand, if you want to improve the quality of your hair, you should use formaldehyde- and chemical-free keratins.
  • In this article, we’ll look at the advantages and disadvantages of each type of keratin. Stay until the end!

Are you planning a keratin treatment and want to know if it’ll straighten your hair?


 Some keratin treatments do straighten hair. They contain formaldehyde. 

Now you know there are two types of hair keratins. Some treatments straighten your hair, and others don’t.

In this article, we’ll look at the advantages and disadvantages of the controversial keratin treatment in its two options.

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Keratin smoothing products with formaldehyde

what shampoo to use before keratin the hair
 Keratin treatments that promise to straighten hair usually contain formaldehyde or some other more or less harmful chemical with the same effect.


Your hair would indeed be visibly straighter, shinier, and look healthier and more beautiful if you get a keratin straightening treatment.

But would your hair really be this healthy on the inside?

What do you think?


The answer is no!

 If you apply keratin with formaldehyde, your hair will look spectacular, but it would only be make-up, it’ll be weakened inside. 


If you apply smoothing keratin just once in your life, nothing magic will happen.  

But I guarantee that if you use keratin with formaldehyde repeatedly, your hair will be completely thinned at the ends and lose density. 


It sounds very tempting to have straight, shiny, and seemingly healthy hair even if it’s just for once, doesn’t it?


Of course, it does. However, can you be sure you won’t fall into the trap again every time you want to have your hair straightened?


I guess not.  Therefore, as a hairdresser and lover of hair health, I strongly discourage any kind of keratin treatments with formaldehyde or any similar chemical ingredient. 


Do you want to know why?

Let’s look at the disadvantages. By the way, you can find smoothing treatments that are kind to to your hair.


Disadvantages of smoothing keratin with formaldehyde

keratin treatment on colored hair

  • Hair becomes addicted to formaldehyde.Later, when the effects disappear, your hair becomes weak and lifeless.
    In my years as a colorist, I have seen manes destroyed by keratin treatments with formaldehyde.
  • Also, formaldehyde sweeps the dye out of the hair and prevents bleaching.
    Therefore, if you usually dye your roots or color your hair blonde, formaldehyde keratin treatments aren’t compatible with either of these two practices.

There are other risks associated with the use of formaldehyde. Its use in cosmetics is generally prohibited.

What hair type is keratin straightener ideal for?

As I told you above, I don’t agree with treatments that contain formaldehyde or any derivative. However, I can’t deny that it helps tame some hair types.

What do I mean by “taming hair”?


Some hair types are hard to style.  It’s usually thick and abundant hair that the stylist needs to work on to look its best. 


In general, it’s not necessary to have a keratin treatment with products that could damage the hair. The keratin smoothing treatment is not advised for women who have damaged or extra fine hair, because it damages the hair fiber and thins the hair.


At this point, you know all about the keratin smoothing treatment. Now, I’ll tell you about formaldehyde-free keratin treatments.


Keratin without formaldehyde or harmful chemicals for the hair

hairdresser applying keratin
 Formaldehyde-free keratin treatments don’t straighten the hair, but help smoothen it. 

Your hair won’t look straight, but it’ll become manageable, docile, and spectacular.


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Formaldehyde-free keratin treatments won’t damage your hair health because they don’t have risky side effects.

The duration of formaldehyde-free keratin treatments will depend on your hair type. If your hair is too untamable, you may have to repeat the keratin treatment every so often.

What about the disadvantages?


Unlike straightening keratin, formaldehyde-free keratin is suitable for all hair types and has no contraindications.


How can you tell if the keratin treatment includes formaldehyde?

  • If care for your hair and opt for a formaldehyde-free keratin treatment, make sure you buy a well-known brand with reliable labels.
  • If you want to apply the treatment at home, don’t buy products of dubious origin without labels.
    Generally, products that don’t include information about the manufacturer and instructions for use on the package contain formaldehyde preservatives that give off formaldehyde.
    They probably use some scent to counteract the toxic vapor. That’s why you should choose quality brands.
  • On the other hand, if you want to have a keratin treatment in a salon, talk to your hairdresser about what you want.
    Ask him/her to show you the brand he/she works with.
    Don’t worry about it. Hairdressers are used to this kind of questions, so don’t be afraid to ask.
  • Another way to tell if the treatment has formaldehyde is if your eyes itch or you feel any discomfort in your throat when it’s applied.
    If you feel irritation or discomfort when you have the treatment, it probably contains formaldehyde.


Conclusion: avoid keratins that straighten hair. They may damage your hair

To sum up, we’ve seen the advantages and disadvantages of straightening keratins. They contain formaldehyde or preservatives that give off formaldehyde.

Now you know why you shouldn’t choose this type of treatment, even if you want to straighten your hair.

 Always choose quality products that have the seal of approval of health authorities in your country.  


And always ask all your doubts to your hairdresser. Don’t let them apply strange treatments without you knowing about them.

I’m sure you’ll make the right choice and your hair will look stunning.

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