Is Teeth Whitening Safe? Kits vs Dentist

Teeth whitening is generally safe when a dentist checks your teeth first and prescribes the gel. The most common side effects are temporary sensitivity and gum irritation. In the UK, only dentists can legally provide whitening with more than 0.1% hydrogen peroxide. At our Kenilworth and Stratford-upon-Avon practices, whitening is £299 until 31 December 2026.

This guide explains the law, the difference between kits and dentist whitening, and why teeth discolour.

What does UK law say about teeth whitening?

Products containing more than 0.1% hydrogen peroxide (up to a maximum of 6%) can only be supplied through a dentist, after an examination, and not to under-18s except to treat or prevent disease. Whitening by beauticians or salons is illegal, and the NHS advises against it.

How are shop kits different from dentist whitening?

• Strength: shop products are limited to very low peroxide levels, so many rely on abrasives or ingredients that only affect surface stains.
• Fit: one-size trays can let gel touch the gums. Dentist trays are made from a scan of your teeth.
• Checks: a dentist looks for decay, gum disease and old fillings first, and reviews you during treatment.

How does dentist-led overnight whitening work?

At Pennington Dental the overnight programme takes about six weeks. For nights 1 to 14 you whiten your upper teeth, with the desensitising toothpaste provided in the lower tray. For nights 15 to 28 you swap, so the lower teeth whiten and the upper tray holds the toothpaste. After night 28 you have a review with Dr Fuz, then usually whiten upper and lower together for about 2 more weeks, depending on sensitivity and comfort.

What are the side effects?

Temporary sensitivity is the most common. Some people get mild gum irritation. These usually settle when whitening stops or is paused. A desensitising toothpaste can help. Tell your dentist if anything does not settle.

What causes yellow teeth?

• Surface staining from tea, coffee, red wine, curry and smoking.
• Age: enamel thins over time, so the yellower layer underneath shows more.
• Inside the tooth: some medicines, injury or developmental conditions can discolour teeth. These may respond less to whitening.

Surface stains can often be reduced at a hygiene visit. Patients can’t book the hygienist directly: book a check-up first and your dentist can refer you (£78.50).

Who should not have whitening?

Whitening is not suitable for under-18s (except to treat or prevent disease) and is usually postponed in pregnancy or while breastfeeding. Decay and gum disease should be treated first.

Frequently asked questions

Is teeth whitening bad for your teeth?

When it is prescribed and supervised by a dentist, whitening is generally safe. Temporary sensitivity and gum irritation are the most common side effects.

Are whitening strips from shops safe?

Legally sold products contain very low levels of peroxide, so they are limited in what they can do. Products bought online from unregulated sellers may not meet UK rules. Ask your dentist before using them.

Is whitening by a beautician legal?

No. In the UK, tooth whitening must be provided by a dentist, or by a dental hygienist or therapist on a dentist’s prescription.

What should I read next?

• Teeth whitening in Kenilworth and Stratford
• Composite bonding

How do I book in Kenilworth or Stratford-upon-Avon?

Find out more about teeth whitening. Your first appointment is a free consultation: book a free consultation.

Call Kenilworth on 01926 863 236 or Stratford-upon-Avon on 01789 205 254, or book an appointment online. Find directions for our Kenilworth practice and our Stratford-upon-Avon practice.

New to us? See our new patient information and the full list of fees on our treatment costs page. To spread the cost of check-ups and hygiene visits, see the Pennington plan.

Further reading: NHS: teeth whitening.

Prices correct at time of publishing (9 November 2026).

Reviewed by Dr Fuz, BDS, BSc, MSc (Restorative Dentistry), GDC 76311. Last reviewed 9 November 2026.

This article is general information and is not a substitute for advice from your own dentist or doctor.