Hydrogen Peroxide Teeth Whitening FAQ

Medically Reviewed By: Dr. Chhaya Chauhan

(GDC Number: 259369)

Hydrogen Peroxide Teeth Whitening FAQ

If you’re researching teeth whitening you may have heard that hydrogen peroxide is part of the process and indeed, it is the main bleaching agent used to whiten teeth.

However, there are some nuances and considerations that you should be aware of, so we’ve listed these in question and answer format below.

If you’re just getting started with this, we advise visiting our teeth whitening hub page, which provides all the information you need on completing teeth whitening safely.

Continue reading for our hydrogen peroxide teeth whitening FAQ.

Does hydrogen peroxide whiten teeth?

Yes, hydrogen peroxide does whiten teeth and is one of the main chemicals used in professional bleaching.

However, using it as part of a professional whitening kit is different to using it as part of a DIY whitening recipe, or in a kit you’ve bought online or in the shops.

Do at-home kits contain hydrogen peroxide?

As laid out in the Cosmetic Product Safety Regulations, in the UK whitening kits that you can buy over-the-counter (OTC) or online are only permitted by law to contain up to 0.1% hydrogen peroxide, which is not enough to bleach your teeth in the same way that professional whitening does.

Professional whitening gel dispensed by a dentist can contain up to 6% hydrogen peroxide.

Is the situation different in the US?

Yes. In the US the law is different as to how much hydrogen peroxide can be included in OTC products.

For example, some whitening strips in the US contain up to 10% hydrogen peroxide, whereas in the UK the limit is 0.1% for OTC products. We have written about this in more detail in our best whitening strips article, and we’ve also written about UK vs US whitening here.

Is hydrogen peroxide used in at-home custom made trays?

Yes, custom made trays, made by your dentist as part of professional whitening treatment, use either hydrogen peroxide or carbamide peroxide as a bleaching agent.

In the video below, I explain the process of having custom trays made:

Watch Our Teeth Whitening Video Course

Is hydrogen peroxide a bleach?

Technically no.  Hydrogen peroxide is H202 whereas the bleach is a basic solution of NaOCl.

Most of us associate bleach with cleaning.  This is usually a dilute solution of sodium hypochlorite.

Both can essentially do the same job, but hydrogen peroxide is a better product for humans and the environment.

Hydrogen peroxide breaks down into oxygen and water and occurs in nature as part of animal and plant cells.

Traditional bleaches have the ability to form more toxic byproducts.

Hydrogen peroxide vs carbamide peroxide: what’s the difference?

Hydrogen peroxide is roughly 3.5 times stronger than carbamide peroxide.

The legal limit for carbamide peroxide as a teeth bleach in the UK is 16%, for hydrogen peroxide it is 6%.

Hydrogen peroxide and carbamide Peroxide are the active ingredients within teeth whitening gels used by dentists.

We talk more about choosing between the two in our professional teeth whitening article.

How long does it take for hydrogen peroxide / carbamide peroxide to whiten teeth?

If you’re using custom made trays, it usually takes 1 to 2 weeks for hydrogen peroxide or carbamide peroxide to whiten teeth.

With hydrogen peroxide, you wear the tray for 2 hours per day, with carbamide peroxide you wear it either during the day or overnight for about 3 to 6 hours.

Where can I buy hydrogen peroxide for teeth whitening?

Only registered dental professionals are able to legally distribute teeth whitening gel that contains hydrogen peroxide.

You can buy this from most dental practices that offer teeth whitening services.

However, to make the purchase, you will usually be required to undergo an assessment to ensure you are suitable for teeth whitening and you know how to properly apply the gel as well as knowing the implications of tooth whitening.

Can you buy your own hydrogen peroxide / carbamide peroxide gel refills online.

Legally, these cannot be sold in the UK. You may find them available online, but they may be counterfeit, so we advise against buying them. We cover this in more detail here.

What does the percentage mean next to whitening gel refills?

This refers to the concentration of hydrogen peroxide or carbamide peroxide that they contain.

In the UK, the legal limit for hydrogen peroxide is 6%, and for carbamide peroxide it is 16%.

In theory any product showing a percentage between 6% and 16% should be referring to the carbamide peroxide concentration, but it may not be so double check.

The reason for this is that in the US, the limit for hydrogen peroxide is higher than 6%. Some sites may therefore be selling US imports to UK residents.

Can you make your own DIY hydrogen peroxide toothpaste or mouthwash to save money?

As a standalone chemical, you can buy hydrogen peroxide at a higher concentration than if you buy it in a whitening kit. It has various uses apart from teeth whitening.

Some people therefore create their own hydrogen peroxide pastes and rinses at home, but we advise against this.

To use it as part of a paste or rinse, the peroxide will need to be of a low enough concentration that it doesn’t burn your mouth. This low concentration means that it will not be strong enough to bleach your teeth.

Besides this, in order to bleach teeth the peroxide needs to be held against them for a sustained period, which is why people wear custom made trays for several hours at a time.

There is the possibility that a peroxide rinse or paste will remove light staining (which is different to bleaching), but even this is doubtful

There are other methods that can remove surface stains more safely, such as using a whitening toothpaste or any abrasive toothpaste periodically, and regularly brushing your teeth.

DIY Hydrogen Peroxide toothpaste rinse

Should I use a DIY hydrogen peroxide paste?

No, as mentioned above we advise against doing this, especially if you have not had a dental check up before hand.

Putting chemicals into your mouth can cause medical issues, and particularly so if you have outstanding dental conditions that need addressing.

If you’re interested in teeth whitening, it makes sense to choose a method that is safe long term. Teeth whitening is only advisable if your teeth are in good health, so you also need to be having regular dental check ups alongside any whitening activity that you or a dental professional carries out.

For more whitening advice, see the official guidelines from the British Dental Association (BDA).

What are the side effects of hydrogen peroxide for teeth whitening?

If used incorrectly, for example if too high a concentration is used, or if you use it for too long hydrogen, peroxide could:

  • Burn the gums, tongue, cheeks and other soft tissue in your mouth
  • Aggravate any existing issues such as cavities
  • Cause inflammation that can then lead to further problems such as infections

If hydrogen peroxide is used correctly, it can still cause issues such as tooth sensitivity. This sensitivity should subside within a day or two after you have used hydrogen peroxide. If it doesn’t, see your dentist.

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