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Why Isn't Hydrogen Peroxide Whitening My Teeth?

All teeth whitening products contain hydrogen peroxide or some derivative of it and that is how it whitens teeth. If what you're using contains it, it should whiten your teeth but sometimes it doesn't seem to work that way.

whitening products with hydrogen peroxide
whitening products with hydrogen peroxide

We're going to go over all of the possible causes which may be contributing to the ineffectiveness of the product that you're using. Yes, it may contain hydrogen peroxide (HP) but there are also other factors which can influence the effectiveness of it.

Factors affecting hydrogen peroxide teeth whitening efficacy:


Delivery method of whitening gel

Whitening products come in various delivery forms that help you apply the hydrogen peroxide onto your teeth.

  • Flexible strips such as the Crest 3D whitening strips.

  • Prefabricated trays like the Opalesence Go.

  • Custom made trays by your dentist.

  • Painted on via a whitening pen.

  • In-office directly painted onto the tooth surfaces

  • Mouthwash

  • Toothpaste

These delivery methods are all used differently but their purpose remains the same, which is to get the hydrogen peroxide onto your teeth. Some of these methods are more effective than others because they may have the ability to ward off saliva and prevent it from touching the gel.

whitening pen
whitening pen

Saliva is the mortal enemy of whitening gels because it naturally contains salivary peroxidase. According to a study by the Journal of Oral Pathology & Medicine, the salivary peroxidase is the first line of defense against hydrogen peroxide. These salivary enzymes can rapidly detoxify it so that it is not harmful to our bodies when we swallow it.

That explains why the toxicology department of the public health of England says low concentration hydrogen peroxide products such as the 3% mouthwash is not harmful to pregnant women. They say that there is no evidence to suggest the unborn child will be harmed since HP gets rapidly detoxified and a very minimal amount actually reaches the bloodstream.

Most effective delivery method

Now that we understand saliva is not good for whitening, the methods which would yield the best results are the ones that keep saliva away. They are ranked in this order in terms of how effective they are in whitening your teeth.

  1. In-office

  2. Trays

  3. Strips

  4. Everything else

in office whitening
in office whitening

The most effective delivery method would be the in-office one since your dentist has a saliva ejector. This is kept in your mouth the entire time, suctioning all of the saliva that may be pooling. This prevents it from touching the hydrogen peroxide, thus making it the most effective way.

The next best option would be trays that you can wear over your teeth. They won't stop the saliva from pooling but the trays can at least act as a barrier against them providing some protection. Of course the customized trays that are made by your dentist would be more effective than the pre-fabricated ones.

What comes after that would be the whitening strips since they can at least hold the gel against your teeth. The flexible strips also somewhat act as a saliva barrier.

The delivery methods with the least amount of protection would be the toothpastes, mouthwashes, and whitening pens. There are no barriers that prevent the saliva from interacting with your product. This means that the effective working time of the whitening is most likely drastically reduced. Nonetheless there are still ways to try to stop your saliva while whitening at home.


Concentration of the peroxide

The concentration has a direct effect on how quickly you can see your teeth get whitened. That explains why a single in-office bleaching session at the dentist can get you whiter teeth almost instantaneously.

16% carbamide peroxide
16% carbamide peroxide

That is in comparison to all of the OTC products that you've been trying to whiten your teeth with for the past year. You've been using the strips, the mouthwash, and the toothpaste but the results were not as effective as an in-office session.

2% peroxide whitening toothpaste
2% peroxide whitening toothpaste

Your dentist is able to achieve the results that they do because they have a much more concentrated product than what you can purchase OTC. Although it does cost significantly more to have it done professionally.


Exposure time to whitening gel

An often overlooked factor which affects the effectiveness of teeth whitening is the total exposure time to gel. A study by the British Dental Journal found that ALL CONCENTRATIONS of hydrogen peroxide can achieve the same level of teeth whitening.

Basically, a 3% HP product can give you the same result as a professionally done in-office 35% treatment. The major differentiating factor is that the less concentrated the product, the longer that you have to whiten for in order to achieve the same level of whiteness.

If you're using OTC whitening strips you will have to whiten for many more days or weeks in order to get to the same level as a single in-office session. The professionally done products simply allow you to get the result faster.

In other words, if it seems like the hydrogen peroxide isn't whitening your teeth, it is most likely that you're using a low concentration product but you just haven't used it for a long enough time. You need to stick with it and keep on whitening for you to see results. If you get impatient you can always pay more and get it done at the dentist.


Using the whitening product wrong

There is also the possibility that you could be using the product wrong and that is why the hydrogen peroxide is not whitening your teeth.

whitening trays
whitening trays

One example would be if you applied the whitening gel to the wrong surface of your trays. You're supposed to put the gel on the cheek facing side of the trays. However if you put them on the tongue facing side, you wouldn't be able to see any color changes.

Another possible cause would be if you forgot to peel off the backing for the whitening strips and you tried to use it as is. If you forgot to do that it your teeth wouldn't even be in contact with the HP.


The whitening gel wasn't refrigerated

There is also the possibility that your whitening gel has been sitting on the shelves unrefrigerated for too long. According to KoR Whitening, when hydrogen peroxide is not refrigerated the heat will slowly start to degrade it. That is why they ship all of their products in an ice box.

Kor whitening comes in ice box
Kor whitening comes in ice box

Thus, the reason why it may not be whitening your teeth could be because its been exposed to heat for too long. However, we haven't been able to substantiate that claim with another scientific study.

Nonetheless, we do see recommendations by another manufacturer such as Opalesence recommending to store their products in the fridge. Their reasoning was that it was to extend the shelf life of their product.

ZOOM whitening on the other hand states that it is not necessary to refrigerate their product.

Due to the mixed messages that we're getting from multiple companies, we would have to say that it is not definitive that refrigeration is absolutely necessary. Perhaps it may help but it doesn't hurt to keep it in the fridge anyway. If you think about it logically, keeping all sorts of chemicals and products exposed to the heat usually doesn't bode well for it.



All products with hydrogen peroxide should whiten your teeth but it doesn't mean that there aren't factors which influence its effectiveness.

In the opinion of our dentists in Long Island City, the two major factors which may influence whether your teeth get whiter is how well you can keep saliva away and also for how long you've been whitening.

In order to maximize the whitening capacity you should do your best to prevent saliva from touching the gel. There are simply way too many enzymes in your saliva that are trying to inactivate the gel that you spent your money to buy.

If you're whitening at home, you're most likely using an OTC product and that means it comes in a lower concentration. For lower strength whitening, you do need to whiten for a longer period of time in order to see the same results. If you're not seeing any changes in your tooth color it may just be that you haven't whitened long enough.

If you want faster results and are not opposed to spending more money, you can always get professional in-office whitening.


David Chen 200 x 200.jpg

About the author: Dr David Chen, DDS

Hello, I'm Dr Chen and I'm an actively practicing dentist in Long Island City, NY. I graduated from Columbia University College of Dental Medicine in 2016 but prior to going to dental school I was already working in the dental field. It's been more than a decade since I first got to know dentistry and let me tell you, time flies by quickly. Since then I've developed a fondness for writing, which is how this all got started!

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Medical Disclaimer:

This blog is purely meant for information purposes and should not be used as medical advice. Each situation in your mouth is unique and complex. It is not possible to give advice nor diagnose any oral conditions based on text nor virtual consultations. The best thing to do is to go in person to see your dentist for an examination and consultation so that you can receive the best care possible.

The purpose of all of this oral health information is to encourage you to see your dentist and to inform you of what you may expect during your visit. Due to the unfortunate nature of dentistry, there isn't really any true home remedies that will get rid of dental problems. Roughly 99.99% of them require in-person intervention by a healthcare professional.

Hint: That is the reason why you can't eliminate seeing dentists in your life!

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