Does hair dye kill lice and nits? Here’s the truth!

Your head is infested. It’s time to top up your hair colour. You need to know, does hair dye kill lice and nits??

It’s the worst nightmare.

You’re washing your hair and suddenly you feel a tickle on your head.

You dive for the mirror, lift up a section of hair to find those little icky black bugs crawling around in your locks. Ew!

Nits! Rather than go through the hair frazzling and raking nit removal process, if it’s time to dye your hair, will it kill them? Let’s find out!

If this has happened to you, we’ve got some good news.

It turns out that if you use permanent hair colour right before shampooing to kill lice, it will work because the dye penetrates down into the roots where they live and feed. Hurrah!

tweet about head lice

What’s the difference between lice and nits?

Head lice are like human fleas. They are teeny, grey/black parasitic insects that can be as big as fleas and resemble tiny earwigs.

They live on human hair and scalp and suck blood to survive, hence the itchiness.

Scarily, they can live up to a month and lay eggs, known as nits, up to five times in one day. Yikes!

Nits are head lice eggs. These are microscopic white specks that are found in clusters on warm parts of the head – typically behind the ear and in the nape of your neck.

Contrary to popular belief, nits don’t care if your hair is clean or dirty.

They are pretty much impossible to wash out without a chemical nit treatment.

Watch and learn: What are nits and head lice?

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Does hair dye kill lice?

Most head lice treatments come in lotions or sprays from your local chemist or supermarket.

They work by suffocating the head lice with chemicals.

Permanent hair dye is said to work in a similar way by suffocating them with the ammonia that the hair dye contains.

To use it this way, use your hair dye normally as instructed but spend extra time rinsing and combing to shake off the dead lice.

Be warned that if you have nits, you’ll still need to use a nit comb and the hair dye may not have successfully killed off all of the lice.

So you may need to follow up with a medicinal treatment after a week or so.

Other hair dyes such as semi-permanent and demi-permanent won’t be strong enough to kill them off as they don’t contain strong enough chemicals to suffocate the little cretins.

Does hair dye kill nits?

Hair dye will not kill nits as nits have a solid shell coating that can’t be penetrated with chemicals.

The only effective way to remove these peky mites is to use a head lice treatment that will coat the hair shaft, making it slippery.

Then, using a nit comb, you can loosen the nits’ grip on your hair by scraping them off.

As you can imagine this is rather damaging for your hair!

So you make sure you condition it well with deep conditioners suitable for coloured hair before and after treatment.

What kind of hair dye kills lice?

The best way to suffocate these pesky head lodgers with a dye that contains hydrogen peroxide or ammonium.

In other words: permanent hair dyes.

These chemicals are responsible for opening your hair cuticles on your hair shafts to allow the hair dye colour in.

They’re also potent lice killers that will suffocate them!

Just make sure you leave your hair dye in for the required amount of time to saturate your hair strands.

Then, you can just go on living your life as usual without worrying about those bugs ever again.

What does hydrogen peroxide do to lice?

Hydrogen peroxide kills adult lice by attacking their central nervous system. Which means no more scratching or itching for anyone involved!

Lice have an exoskeleton that is sensitive to high concentrations of hydrogen peroxide.

This means that the louse will die if exposed to 30% or more of this chemical for a long enough time.

Exactly as long as it takes to dye your hair!

How long does it take for hair dye to kill lice?

Here are some tips on how long you should leave the dye in your hair before washing it out.

If you have a lot of thick or coarse hair, expect to leave the colourant for at least 45 minutes.

For those with fine or thinning locks, this will be less time – around 20-25 minutes should do the trick!

To avoid staining clothes and other items in your home use rubber gloves while applying the dye and make sure to cover all surfaces possible with plastic sheets before proceeding.

This way you’ll also avoid any accidental drips down your arms as well as stains on furniture from wet hands.

The hair dye will work by coating each strand of hair with a protective layer that prevents lice from attaching themselves to your head, so they die within 24 hours.

Can I use a nit treatment if I’ve just dyed my hair?

Its needs must if you have nits and you need to act fast to kill off the head lice.

Not to mention get rid of the discomfort of sharing your head with blood sucking beings!

So while it’s not a great process to do if you have dyed hair, it’s a necessary one. The sooner you do it the better.

Just make sure you use deep conditioners before and after the process to replenish and restore the moisture in your hair as much as possible.


  • Use permanent hair dye only. Only hair dye that contains ammonia will kill head lice.
  • Use hair dye to kill nits only if you’re due to dye your hair anyway. You’ll still need to go through the regular nit removal treatment and process.
  • Condition your hair with deep conditioners suitable for dyed hair before and after the process to restore moisture to your hair and smooth the hair shaft.


  • Don’t use hair dye specifically for the purpose of killing head lice. Medicinal treatments will be more effective in the long run.
  • Don’t worry if you have dyed your hair recently. You are likely to notice it affect the condition of your hair more than the colour.
  • Don’t dye your hair straight away after using nit and head lice shampoos and treatments. Wait for at least a week for your hair to regain some natural oils and elasticity so it’s strong enough for hair dyeing.

Parting words

So if you want to get rid of those pesky little cretins and give yourself a make over in the process, you can go ahead and kill them with permanent hair dye.

Good luck!

Find out more answers to common hair dye questions over on our hair dye FAQs page.