Your Guide to Tooth Whitening
A balanced guide to professional tooth whitening: how it works, what results to expect, who it suits, and the risks you should know about.
What is tooth whitening?
Tooth whitening is a cosmetic treatment. It makes the natural colour of your teeth lighter. It does not take away any of the tooth surface. A bleaching gel changes the colour of the outer layer (enamel) and the layer under it (dentine).
In the UK, only these people may do tooth whitening:
- a registered dentist
- a registered dental hygienist, dental therapist or clinical dental technician working to a dentist's prescription
It is illegal for beauty salons or other non-dental businesses to do tooth whitening.
Under UK cosmetics law, some whitening products can only be provided by a registered dental professional after an examination. These are products that contain or release more than 0.1% hydrogen peroxide. Products stronger than 6% cannot be used for cosmetic whitening. For home use, a dentist may prescribe products with up to 6% hydrogen peroxide. Or they may prescribe up to 16% carbamide peroxide. This releases the same amount of hydrogen peroxide.
Illegal or unregulated whitening products may contain much stronger bleach. They can cause serious and permanent harm to your teeth and gums.
Types of professional whitening
Your dental team may offer one or more of these options:
- Home whitening (with trays). Made-to-measure trays are fitted to your teeth. You fill them with a whitening gel your dentist prescribes. You wear them at home, usually for 30–60 minutes a day for 2–4 weeks. By law, the first application of each course of home whitening must be done by your dentist or under their direct supervision. You then finish the course at home. This is the approach most often advised. It gives reliable, lasting results.
- In-practice whitening. A stronger bleaching gel is put on your teeth at the practice. A light or laser may be used to activate it. Results are faster, but you may need a top-up at home. Sensitivity during and after treatment is common.
- Both together. In-practice whitening, followed by home whitening trays to keep the result.
Who is suitable for tooth whitening?
Most people with healthy teeth and gums can have whitening. But it is not right for everyone:
- Whitening does not work on crowns, veneers, or tooth-coloured fillings — these will remain their original shade. This may mean they no longer match your teeth.
- Teeth stained from the inside may not whiten as well with standard whitening. This includes stains from an injury, from tetracycline antibiotics, or from fluorosis.
- Whitening is not advised if you are pregnant or breastfeeding.
- Whitening for cosmetic reasons is not allowed for anyone under 18. Your dentist may still use a whitening product for a young person when it is needed to treat or prevent a dental problem.
- Any active gum disease or tooth decay should be treated before whitening starts.
What results can I expect?
Whitening can make your teeth a lot lighter. But results vary from person to person. It helps to know what to expect:
- Most people see their teeth get several shades lighter.
- Yellow-toned teeth whiten better than grey-toned teeth.
- Results do not last for ever. Teeth naturally yellow again over time. You will need regular top-ups to keep them white.
- Smoking, coffee, tea, red wine and some foods stain teeth. They make the result fade sooner.
Risks and possible side effects
Common (affect more than 1 in 10 people):
- Tooth sensitivity. This is very common. Your teeth may hurt more with hot, cold and sweet things. This happens during whitening and for a short time after. It usually goes within a few days of stopping the gel. Toothpaste for sensitive teeth can help.
- Sore gums if the gel touches them. Made-to-measure trays greatly lower this risk.
Uncommon:
- Uneven results. Some areas may whiten more than others.
- Sensitivity that lasts more than a week after treatment
Rare:
- Serious gum damage from badly fitting trays or using too much gel
Whitening gels from UK dentists contain hydrogen peroxide at safe strengths set by law. Some products are sold illegally online or outside dental practices. These may contain dangerous amounts of bleach. They can cause permanent damage to teeth and gums.
Making your results last
- For at least 48 hours after whitening, avoid food and drink that stain. These include coffee, tea, red wine, berries and tomato sauce. Your teeth stain most easily at this time.
- Drink staining drinks through a straw when you can.
- Brush with a good whitening toothpaste to help keep the result.
- Keep your trays. Top-up whitening at home costs much less if you already have them.
- You will usually need a top-up every 6–12 months to keep the result.
- Do not smoke. Smoking is one of the fastest ways to stain teeth again.
Questions to ask your dental team
- Are my teeth and gums healthy enough for whitening?
- Will my fillings or crowns still match after whitening?
- Which whitening option do you suggest for me?
- How many shades lighter can I realistically expect?
- How long will my results last, and how do I top them up?
This leaflet is for general information only and does not replace professional dental advice. It is intended to support — not replace — the discussion with your dental team about your individual options, risks, and treatment plan. Treatment outcomes vary between patients depending on individual circumstances. Your dental team will confirm exact fees and what is suitable for your specific circumstances before you agree to any treatment.
Sources
- Position statement on tooth whitening. General Dental Council (GDC), 2016.
- The Cosmetic Products Enforcement Regulations 2013 (SI 2013/1478). UK legislation (legislation.gov.uk), 2013.
- Teeth whitening. NHS website (nhs.uk), reviewed August 2025.
Links checked 18 October 2026.
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