How long does heat protectant last? It lasts until you start straightening your hair

flat iron your hair in the morning

  • The heat protectant lasts until you start straightening, blow-drying, or curling your hair with heat tools.
  • As you curl, blow-dry, or flat iron your hair, the protectant evaporates to prevent your hair from dehydrating due to high temperatures.
  • The heat protectant coats the hair with silicones that form a film to protect the hair from high temperatures. That film disappears when you apply excessive heat.


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It’s as easy as that.

The heat protectant is not a hair moisturizing or nourishing treatment.

Instead, it protects the hair from the high temperatures of styling tools.


 In other words, the heat protectant starts working the moment you straighten or flat iron your hair. And it lasts until you finish using the tool. 

Why does it last so short?


It’s because it doesn’t penetrate the hair core. It simply forms a protective film that is activated by heat.


  • If you apply the protectant the previous night and didn’t flat iron your hair, the product will still be in your hair.
  • However, if you get up and flat iron your hair, the protectant will disappear as you straighten each of your strands.


It seems almost like common sense.

Unbelievably, many of my clients are confused about how long the heat protectant lasts on their hair once they apply it.


protect hair from the heat of the flat iron

And speaking of clients, this reminds me of one of them. Her name is Anahi.

She recently came in to touch up her blonde hair color. I noticed her hair was quite coarse. Since I’ve known her for many years, I know her hair habits.

Therefore, I know that Anahi irons her hair, at least twice a week.


In fact, what Anahi does is flat iron her hair on Mondays, for example. Then, on Wednesdays, she uses the flat iron again on some strands without washing her hair.

I asked her if she was using the protector. And she answered with such a blunt “Obviously!” that I had no choice but to believe her.


Still, I insisted. “Anahi, do you use the protectant every time you flat iron your hair?” At that moment, the look on her face changed.

And she confessed that she actually used it only one day a week after washing it.

She didn’t apply it on Wednesday or the following time she used the flat-iron.



Because she thought the heat protectant was still effective after several days.

Do you see the mistake?


 She didn’t use the protectant when straightening some waves after the first time. 


As we said before, the silicones in the protectant had evaporated after styling the first time.

So, if you curl or flat-iron your hair frequently, and even if you use a blow-dryer, you should know how it works and how long it lasts.

Now, let’s go deeper into these issues.

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The heat protectant lasts until you style your hair with heat

protect hair during drying

The heat protectant is activated by heat.

Studies have shown that heat protectants are effective for the hair when you’re going to use heating tools. It gives the hair an extra layer of protection to protect it from drying out and damaging.

Did you know that your hair is 70% water?


Water molecules inside the hair give it shine, softness, and body.

If you’ve ever flat ironed, curled, or even blown-dried your hair, you may have noticed that there’s steam.


And that’s not because your hair is burning. That steam is simply water evaporating from the heat of the flat iron or curling iron.

What does the protectant do?


 It prevents the water in your hair from evaporating. 


So, when you apply the protectant, and then flat iron your hair, the silicones in the protectant will evaporate (not the water in your hair)


When you flat iron or curl your hair, those silicones are activated and create a protective barrier to retain moisture.


 Therefore, the heat protectant is only activated by heat. When you finish styling your hair, it’ll be completely gone. 

That’s why, every time you heat style your hair, you need to apply a heat protectant.


What happens if I apply the heat protectant and wait several days to flat iron or curl my hair?

do not use heat tools before bleaching

The silicones in the heat protectant will disappear and not protect your hair from heat damage.

External factors such as sweat, the sun, the rain, or even you touching your hair will degrade the silicones deposited on the outside of your hair.


 So the protectant will last until you flat iron or curl your hair as long as it’s a few hours later or the following day. 


And remember that you need to wait until the heat protectant has dried before you style it with heat tools.

Heat protectants have different consistencies. Some are thicker, like oils, and others are lighter, like sprays.

So, your hair must air dry before flat ironing or curling whether you used a heat protectant or not.



The heat protectant lasts until you straighten or curl your hair. At that moment, the heat activates and evaporates the silicones in the heat protectant.

You can apply it a few minutes before using heat tools or the night before. And remember that the protectant must air dry before you style your hair.

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