Did You Just Swallow Saliva With Crest Whitening Strips?

Written & Reviewed by Dr David Chen

So you’ve been using the Crest white strips because you wanted whiter teeth. However, what you’ve noticed is that the instructions tell you to wear the whitening strips for 30-60 minutes (depending on which product). But, there are no instructions as to what you should do with all of that saliva during that time frame.

crest white strips - displayed with all of the packets

This is what usually happens: After a couple of minutes of having the strips on, saliva starts pooling and you look like a dog with rabies that is foaming at the mouth.

Seriously, what do you do with the saliva? Can you swallow it or is that dangerous? Well, ponder no further because we’re going to answer your question today.

Can I swallow with crest white strips?

Instructions from Crest do not explicitly say whether or not you should swallow the saliva while wearing their whitening strips. In fact, they don’t mention what you should be doing with it either such as spitting it out or otherwise.

These are all of the instructions for how to use the strips from their website:

  • APPLY. Peel the upper and lower strip from plastic backing liner and apply strips to upper and lower teeth. WEAR FOR 30 MINUTES. DO NOT REMOVE THE TEETH WHITENING STRIPS YET.
  • HOLD. To start the light treatment, press and hold the two buttons on the sides of the device simultaneously to turn on light, then release.
  • LIGHT. Place the light against strips for 5 minutes. Light will turn off after 5 minutes. Then remove the light and strips. Peel strips from back of teeth first to ease removal.
  • SMILE. Reveal your whiter smile.
Crest white strips - One Hour Express LED Light 4 Steps
Credit: Crest

It does a great job at telling you how to use their product by distilling it down to four simple steps. Unfortunately it does not tell you about what to do with the saliva.

Crest Addenum

However if you do a little bit of further digging, you’ll find a brief article from Crest about how swallowing saliva while using their strips is not harmful.

No adverse effects will result from ingesting the peroxide gel. It will simply pass through your system without causing any damage. However, swallowing large amounts of peroxide can cause nausea and stomach irritation.


It’s great that the source is telling us that it isn’t harmful if you swallow it. But does that mean you should be gulping all of that saliva down or what? That question has yet to be answered.

Is the saliva mixed with the crest whitening strip harmful?

According to Crest, there shouldn’t be any adverse effects from swallowing the saliva mixed with their strips. But here at afterva, we don’t like to take statements at face value without scientific research to back it up. Crest is a very credible source but we still prefer to have more concrete evidence.

crest white strips - front of strip packet

We found a study in the NIH database which states that hydrogen peroxide gets rapidly detoxified once it gets absorbed. Therefore it is not likely to cause a problem but just to be clear, this is for low concentrations.

This is relevant because hydrogen peroxide happens to be the primary whitening agent in the crest white strips. The whitening strips work by utilizing a flexible strip that holds the peroxide against your teeth to whiten them. Essentially all whitening products work in a similar way, its just the way they apply the gel to your teeth differ.

In addition to the peroxide getting detoxified upon absorption, it also gets broken down in the mouth. Our saliva actually contains a lot of natural salivary peroxidase, which are enzymes that degrade hydrogen peroxide. It is a defense mechanism against bacteria but it also happens to work against whitening gels.

The importance of that is that saliva is mortal enemy of teeth whitening. It is preferable to NOT have saliva being in contact with the peroxide gel because it decreases its effectiveness. This is one of the reasons why in-office whitening is superior to DIY products. Your dentist has a saliva ejector that can suction up excess saliva during the treatment.

In conclusion, for low concentration whitening products like the crest white strips it is probably not harmful if you accidentally swallow some of the saliva. Your body will rapidly detoxify it when it gets absorbed and your saliva will naturally degrade it as well.

What you should do with the saliva

We’ve two recommendations as to what you can do with the saliva while wearing the Crest white strips.

  • Swallow the saliva before they touch the strip.
  • Gently spit out the saliva as it pools.

Swallow the saliva immediately before it pools

In our opinion, the simplest solution is to actually swallow the saliva right after it starts to pool. If you continually keep swallowing, the saliva will not be able to touch the strips nor interfere with your whitening process.

In fact, you can make the process even more effective by laying down on a sofa or on your bed. That way the saliva does not pool towards the front of the mouth where the whitening strips are.

Laying down will force the saliva to collect towards the back of the throat. You can give this method a try and see how you feel about it.

What does whitening strip saliva taste like?

When we tested out the Crest white strips and swallowed the saliva, it didn’t taste bad per say. It just had a slight plastic taste to it which comes from the strips. It wasn’t bitter as you may have imagined.

Gently spit out saliva

One solution is to gently spit out the excess saliva that is pooling in your mouth while you’re whitening with the crest strips. You want to do it gently so you don’t disturb the strips and accidentally detach them from your teeth.

You may want to use this method if you don’t want to purposefully swallow the potential residual peroxide. After all, peroxide isn’t exactly food.

Even Crest admits that swallowing “large quantities” of peroxide can cause stomach irritation and also make you nauseous. If you spit out most of it, then you’ll only be accidentally swallowing “small quantities” of it, which is indefinitely safer.

We don’t want to scare you but there have been case reports about people ingesting either large quantities of it or very concentrated peroxide. The results were LETHAL in all of these cases.

Cases resulting in death from hydrogen peroxide ingestion

There was a major study from a European Union Risk Assessment Report that had unfortunate and devastating results from hydrogen peroxide ingestion.

The first case was of a 2 year old boy who swallowed 4-6 oz of 35% hydrogen peroxide (HP) directly. The boy became rapidly unresponsive and unfortunately passed away four days later. Of course that concentration is multiples of what you would find in whitening strips but it serves as cautious reminder that it can be dangerous.

The second case was of a 16 month old boy who was playing with a bottle of 3% hydrogen peroxide. He ended up swallowing about 230 g of it and started foaming at the mouth. The boy died 10 hours later.

hydrogen peroxide - medicine cabinet

This concentration of peroxide for the second case is roughly similar to what you would find in the crest whitening strips. It is the exact potency as that little brown bottle of peroxide you’d find at the pharmacy.

That is actually kind of scary but you do have to take into account that it was an infant who does overdose a lot easier than an adult. They were also directly swallowing the solution, which is different from you applying it on the teeth. Some of it gets used up by the tooth and the rest gets degraded by salivary peroxidase.


If you accidentally swallow some of your saliva here and there while using the crest whitening strips, you shouldn’t worry. According to most research and from Crest itself, it will most likely not cause you any harm.

However that doesn’t mean you should purposefully gulp down all of that saliva which is mixed with hydrogen peroxide. That is simply a risk that you don’t have to take because it can be harmful when done in large quantities.

The recommendation is to gently spit out the excess saliva while you’re whitening so that you don’t disturb the strips. It is safer since you’re not ingesting it and also helps the gel work better since saliva naturally tries to inactivate the peroxide.

Overall it is safe to whiten your teeth with the strips as long as you follow the directions properly. You’re really only doing the treatment for a week or two anyway. Also according to Crest’s directions, you’re really only supposed to use two boxes of whitening per year. That is basically how often you’re supposed to use the whitening strips.

Essentially you wouldn’t be swallowing the peroxide saliva all year round so it should be safe. Although it would be a different story if you had bleachorexia where you were whitening 365 days a year… Now THAT may qualify as swallowing a large quantity.


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