Understanding Hydrogen Peroxide Whitening Benefits

It is evident that take-home teeth whitening products are trending. What are the reasons? Evidence strongly backs the effectiveness of do-it-yourself (DIY) teeth whitening kits. Let’s get into the science behind how the active bleaching ingredient - hydrogen peroxide - actually lifts stains and whitens teeth.
Most openly, even professional dentists and hygienists, acknowledge that over-the-counter teeth whitening products work. Few though know the science behind how hydrogen peroxide actually whitens teeth. Understanding the science, or chemistry specifically, will clarify the question on whether hydrogen peroxide is safe to use or not.

Teeth Whitening: The Science

Teeth Whitening

Teeth Stains

Teeth discolour and stain for many reasons. Age, smoking, diet, and genes all can play a role. Understanding why our teeth discolour will help clarify how hydrogen peroxide can lift tooth staining and whiten teeth.

Our teeth are made up of three different layers. Two of the three layers - the enamel and the dentin - can and will discolour. The pulp is the third inner tooth layer, but is made up of nerves and blood so does not play a factor in tooth staining. The two types of discolouring that will occur are called intrinsic and extrinsic stains.  

Teeth Stains

Intrinsic teeth stains, also called internal stains, are found in the softer middle dentin layer of the tooth. It is softer than the outer enamel layer. Stains here are caused mostly by age, genes, antibiotics, excess fluoride, and tooth decay.  Intrinsic stains are harder to lift or bleach, being located under the enamel.  

Internal stains are not the target of most DIY or take-home teeth whitening products. Seeing a professional dentist might be the most effective way to fight internal teeth staining. 

Extrinsic stains, or external teeth stains, appear on the enamel outer layer of the teeth. This is the most common type of teeth staining and is where over-the-counter teeth whitening products are most successful. Smoking, diets, and bad dental hygiene often are the culprits for extrinsic teeth stains.

Intrinsic and extrinsic stains both are composed of colourless chemical compounds that can pigment - chromogens. These chromogens stick to the enamel and can actually produce their own pigments, which causes both types of tooth staining.

It is important to understand that our teeth are not naturally blinding white. They often are a few shades darker. Understanding this can offset misunderstood frustration when going through the teeth whitening process.


Stain Producer




Tar and Nicotine


Tar/Dark  Nicotine/Yellow




Yellow, Brown, Orange


Enamel thins with age




Enamel varies in thickness/colour



Excess Fluoride

Fluoride build up 


Off White, Brown, patches, spots

Hydrogen Peroxide

Hydrogen Peroxide

So how does hydrogen peroxide whiten teeth? The whitening process is known as oxidation. Chemically, this is called a redox reaction. Chemical compounds that are oxidised lose electrons causing the whitening of teeth. Rusting is a common redox reaction that most of us are familiar with. There are several types of redox reactions¹, that we will not delve into, but the basics are needed to understand the science behind hydrogen peroxide and teeth whitening.

Two main chemical compounds are used in teeth whitening oxidation.  Carbamide peroxide and hydrogen peroxide are found in most quality teeth whitening products. Hydrogen peroxide is the active bleaching agent that oxidises. Carbamide peroxide breaks down into hydrogen peroxide when in contact with the teeth. Oxidation of the hydrogen peroxide breaks down the chemical bonds of the pigmented chromogens. 


The breaking down of these chromogens via oxidation scatters the molecules, lightening the colours of the chromogens, thus lifting the stains and whitening the teeth. This oxidation process is the punch behind effective DIY teeth whitening.

Using hydrogen peroxide as the active bleaching agent is perfectly safe. Mild risks occur predominantly in cases where there is blatant over exposure to hydrogen peroxide. Side effects include discomfort in the mouth, high tooth sensitivity, and mild gum irritation.  Always follow product instructions.


It is perfectly understandable to have reservations when first considering over-the-counter teeth whitening products. Do DIY teeth whitening kits work?  Is hydrogen peroxide safe to use to whiten teeth? What shade of white should my teeth be? Why are my teeth getting darker?

These are all legitimate questions. Hopefully understanding the science behind hydrogen peroxide oxidation, how it lifts stains and whitens teeth, lays to rest any concerns or reservations about trying it out. Join millions of others who have decided to whiten their teeth at home.

Understanding why your teeth change colour and how to whiten them will save you thousands of dollars, not mentioning hours spent in a dental chair, as you brighten your smile. Take a look at a safe, quality, and effective DIY teeth whitening product lineup here.