Hydrogen peroxide tooth-whitening (bleaching) products: Review of adverse effects and safety issues

A summary of: Tredwin, C., Naik, S., Lewis, N. et al. ‘Hydrogen peroxide tooth-whitening (bleaching) products: Review of adverse effects and safety issues.’ Br Dent J 200, 371–376 (2006). https://doi.org/10.1038/sj.bdj.4813423

The desire for whiter teeth has grown in popularity amongst the public. Going to the dentist to get teeth professionally whitened is more expensive than doing it yourself at home, attracting people to the idea of whitening their teeth using chemicals at home.  

Tooth whitening is the process that lightens the colour of a tooth by removing the stain by physical action; or using a chemical reaction to make the tooth a lighter colour.

Tooth bleaching can be done by a dentist at a practice; provided by a dentist to carry out at home; or bleaching products are sold over the counter in strips/night trays.

It has been reported in early 2022 that over 6 million people in the UK have had their teeth whitened.

The Dentist. (May 2021.). The Dentist – UK public among the most interested teeth whitening.

Types of bleaching

Tooth bleaching is primarily based on hydrogen peroxide or carbamide peroxide 

The bleach products target the chromogens (colour agents) within dentine, reducing the colour of the tooth.

These bleach products can be applied either externally via ‘vital bleaching’ or internally, within the pulp chamber, via ‘non-vital bleaching.’


Hydrogen peroxide (H2O2) or Carbamide peroxide gel are the common ingredients present in most whitening products. 

Negative side effects

Tooth sensitivity is a common harmful effect from tooth whitening.

In a clinical study, 15-65% of patients were seen to have increased tooth sensitivity after using 10% carbamide peroxide. A greater percentage of tooth sensitivity, 67-78%, was reported after using hydrogen peroxide to bleach teeth.

In a clinical study, comparing 2 different brands of 10% carbamide peroxide bleaching agent, 55% of the 64 patients claimed they had tooth sensitivity and gingival irritation. Twenty percent of these patients decided to terminate the tooth bleaching treatment due to the discomfort. In turn, it has been deduced that patients with vulnerable soft tissues should avoid products containing H2Oand carbamide peroxide. 

Additionally, there have been many studies suggesting H2O2 is carcinogenic. Therefore, it is recommended to have gingival protection when using such bleaching agents.  


Overall, here we have explored tooth whitening and its negative effects. It is evident that there needs to be more education around the topic of bleaching due to its harmful consequences, as it is idealised in the eyes of many. However, more research needs to be done to clarify whether the benefits of H2O2 whitening outweighs its disadvantages.

Research summary written by: Tamara Al-Sabah, University of Manchester – BDS 2

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