Medical review: Based on peer-reviewed research and guidelines. Clinical review by a Dalian Speciality Dental Clinic dentist is pending. This page is general information, not a diagnosis. Please see a dentist about your own teeth.
How whitening works
Most whitening products use hydrogen peroxide, or carbamide peroxide, which breaks down into hydrogen peroxide. The peroxide enters the tooth and lightens the stains. Products differ in strength and in how long they stay on the teeth.
What are the side effects?
Reviews of the research describe two common ones:
- Tooth sensitivity, usually temporary.
- Irritation of the gums.
Other, rarer effects have been reported, particularly with strong products or prolonged use. Review authors recommend using low concentrations and avoiding prolonged, concentrated exposure.
How to reduce the risk
- Have your teeth examined first. Untreated cavities, gum disease or worn enamel can make whitening uncomfortable.
- Follow the instructions exactly, and do not use products for longer than directed.
- Choose low-dose products and avoid prolonged, concentrated exposure, as review authors recommend.
- Ask your dentist about professional whitening, which is supervised.
What whitening cannot do
Whitening does not change the colour of crowns, veneers or fillings, and it works best on natural teeth stained by food, drink or age. Deep staining or damaged teeth may need a different treatment, such as veneers.
When to see a dentist
Stop and see your dentist if you have strong or lasting sensitivity, painful or bleeding gums, or white patches on the gums.
Frequently asked questions
Does whitening damage enamel?
The main documented effects are temporary sensitivity and gum irritation. Using products as directed, at lower strengths, reduces risk. Ask your dentist what is suitable for you.
How long do the results last?
It varies from person to person and depends on habits such as coffee, tea and smoking. Your dentist can advise on keeping results.
Is whitening safe in children?
Speak to a dentist before whitening a child's or teenager's teeth. They can check the teeth and advise what, if anything, is suitable.
Sources
- Hydrogen peroxide tooth-whitening (bleaching) products: review of adverse effects and safety issues. British Dental Journal, 2006.
- Undesirable and adverse effects of tooth-whitening products: a review. Clinical Oral Investigations, 2010.
Information can change as new research is published. Last reviewed 6 November 2026.
