Can You Leave Hair Dye Overnight? Hair Advice from the Expert

dyeing hair traditional black vs jet black

You shouldn’t leave hair dye overnight.
If you leave permanent hair dye overnight, your hair will be weaker and brittle. Also, the color will fade after a few washes.
Alternatively, leaving semi-permanent hair dye overnight won’t help it settle because the scalp oil will prevent it. It can also cause scalp irritation.

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No, no, and no.

Non, non, non.

Não, não, não.

不,不, 不, 不.

To make it clear, I said it in four different languages: Spanish, Italian, Portuguese, and Chinese.

In case it’s not clear, I even say it to you in Esperanto: ne, ne, ne.

Indeed, you shouldn’t leave any hair dye overnight.

I’ll tell you about Andrea, one of my clients.

Three days ago, she came into the salon in desperation.

Believe me, she wasn’t over-reacting.

Her hair was ruined.

Do you know what ruined hair is?

It has split ends.
It’s impossible to untangle.
There’s too much frizz.
It’s very rough.

This is what Andrea’s hair looked like. What had happened?

She had left the dye overnight.

I don’t know where she got the idea.

Well, actually, I can imagine.

She’d probably seen some “fancy” tutorial on YouTube, though she’ll never admit it.

Why did she leave the hair dye overnight?

She said she was tired. She had applied the dye after dinner and when it was time to rinse it out, she felt sleepy.
She thought that if she left the dye overnight, the color would be better, more intense, and brighter.

What were the results?

Leaving the dye in overnight severely damaged her hair.

After three washes, there was no trace of the color left.

How did I fix it?

I trimmed ten centimeters off her hair.
I dyed her hair again, but I had to include Olaplex to repair the damage.

In other words, Andrea had to give up several inches of her hair and spent a lot more money to dye her hair again.

The result is the same whether you use permanent or semi-permanent dye. Each type of hair dye has a maximum exposure time that you must respect.

The permanent dye is left on for a maximum of 45 minutes.
The semi-permanent dye is left for a maximum of 30 minutes.

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If you leave it on your hair all night, the consequences can be very unpleasant.

Let’s start with permanent hair dye.

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If you leave your permanent hair dye overnight, your hair will be damaged and the color won’t last as much

semi permanent dye in bowl

The permanent hair dye is applied with a 20-volume developer.

The developer is a chemical product that opens the hair cuticles to help the color settle in.

How is the color fixed?

Due to ammonia, which is another chemical.

The coloring process gives your hair an even and shiny color.

But what happens when you apply permanent hair dye every four to five weeks to touch up the color?

Your hair loses moisture with each coloring job. Also, brittle ends and frizz start to appear.

In other words, your hair weakens.

If you care about your hair’s health, you should nourish it at least once a week to balance the effects of the processes.

Coloring your hair takes 45 minutes and moisture is lost. Can you imagine the consequences of leaving the dye overnight, or say eight hours?

Can’t you imagine?

Let me summarize what happens if you leave the dye overnight.

When the cuticles open and your hair absorbs the dye, it’ll start to change color. This happens after 45 minutes of exposure.
After two hours of exposure, your hair will continue to absorb the dye and distribute it from root to ends like nutrients.
Actually, your hair will absorb the dye chemicals all night long. That will dry out your mane from root to tip.
The following morning, your hair will be saturated with degraded chemical residue.
When you rinse out the dye, you’ll lose much of the color because your hair will expel the excess.
Then, it’ll be impossible to detangle your hair. It’ll be so dehydrated and weak that it’ll end up breaking the moment you comb it.

Therefore, leaving the dye overnight will ruin your hair.

You’ll need to color it again after a few washes.

However, if your hair is badly damaged, you won’t be able to dye it again.

Instead, your hair will need intensive moisturizing treatments as Andrea’s did. She had to use Olaplex the following time.

If you leave the semi-permanent hair dye overnight, the scalp oil will prevent the product from settling

dye hair at home

But dye can also cause scalp irritation.

Yes, although semi-permanent hair dye isn’t applied with a developer and doesn’t contain ammonia, it must be used appropriately.

The maximum exposure time is thirty minutes.

If you leave it on longer than that, nothing good will happen to your hair. Not to mention leaving it overnight.

The semi-permanent hair color adheres to the hair forming a film. That film will also form on the scalp and the pores will become clogged.

If the pores become clogged, they can’t properly expel the natural oil to hydrate your follicles and absorb nutrients to keep your hair healthy from root to tip.

What will happen then?

The natural oil will prevent the semi-permanent dye from settling properly. Then, your roots will have faded color.
As the pores are clogged, the scalp will become dry and irritated , giving way to unbearable itching.
The following morning, your hair will be over-toned. When you rinse it out, most of the dye will fade.

Now you know.

If you color your hair with a semi-permanent hair dye, leaving it on overnight will cause scalp irritation and color fading.