Oral Health›Common problems

Stained and Discoloured Teeth: Causes and What Can Be Done

Teeth can be stained on the surface by food, drink and smoking, or discoloured from within by injury, some medicines, fluorosis or age. Here is what causes each, what a dentist can do, and the rules on whitening.

Updated September 2026·By the OHA editorial team·8 min read·How we write
Key takeaways
  • Surface stains come from things like tea, coffee, red wine and tobacco, and often respond to a professional clean or whitening.
  • Stains inside the tooth can come from injury, some medicines taken while teeth were forming, fluorosis or ageing, and are harder to shift.
  • Whitening only works on natural teeth, not on crowns, veneers or fillings, and is not suitable for everyone.
  • In the UK, only registered dental professionals, on a dentist's prescription, can legally whiten teeth. In Australia, only registered dental practitioners can use high-strength products.
  • Side effects such as sensitivity and sore gums are common but usually short-lived.

Teeth can become stained or darker for many reasons. The Australian Dental Association says dental practitioners are best placed to work out the cause and advise whether whitening would help.

What causes stained teeth?

Discolouration is usually divided into stains on the outside of the tooth and stains inside it. Some people have both.

Surface (extrinsic) stains

Extrinsic stains sit on the surface of the enamel, the hard outer layer of the tooth. Causes listed by the Australian Dental Association, healthdirect Australia and the American Dental Association include:

  • Drinks such as tea, coffee, red wine and cola. The Australian Dental Association explains that their strong colour pigments attach to the enamel and make it look darker.
  • Foods such as spices, berries and beetroot (healthdirect).
  • Tobacco. The Australian Dental Association says tar and nicotine can turn teeth yellowish. See smoking, vaping and oral health.

The American Dental Association says smoking, chewing tobacco and poor oral hygiene can make surface stains worse.

Stains inside the tooth (intrinsic)

Intrinsic stains are within the enamel or the dentine, the yellowish layer underneath it. Causes include:

  • Injury. The Australian Dental Association says a knock can make a tooth darker over time, either because the tooth makes extra dentine to protect the pulp (its soft centre) or because blood from inside the tooth leaks into the surrounding structure.
  • Some medicines. Taking the antibiotics tetracycline or doxycycline while the adult teeth are forming, for example during pregnancy or as a baby, can stain them (Australian Dental Association, healthdirect). The American Dental Association adds long-term use of chlorhexidine, an antiseptic mouthwash.
  • Fluorosis. Too much fluoride while teeth are forming can cause dental fluorosis. The Better Health Channel (Victoria) describes fine, pearly-white flecks or lines that are usually very hard to see, and says it does not affect how teeth work. The Oral Health Foundation says it is usually mild and rare. See fluoride explained.
  • Getting older. The enamel thins with age, letting more of the yellower dentine show through (Australian Dental Association, healthdirect).
  • Fillings, root canal treatment and decay. The Australian Dental Association lists amalgam (silver) fillings and root canal treatment, and the American Dental Association lists tooth decay.

What can a dentist do?

The first step is an examination to find the cause. The NHS says a dentist should check your teeth and gums are healthy before you try whitening.

  • Professional cleaning. The Australian Dental Association, healthdirect and the American Dental Association all say this can reduce surface stains. Whitening toothpaste can also reduce surface stains (healthdirect, Australian Dental Association), though healthdirect notes it can make teeth sensitive.
  • Whitening (bleaching) uses a gel containing hydrogen peroxide or carbamide peroxide to lighten the enamel. It can be done in the dental chair, often with a light or laser, in one appointment of around 1 to 2 hours (NHS). Or the dentist makes trays that fit your teeth closely, with a gel you use at home, usually for 2 to 6 weeks (NHS). The NHS says the effect is not permanent but may last around 3 years.
  • Internal bleaching is for a tooth that has darkened after root canal treatment. A whitening gel is placed inside the tooth for several days and the tooth is then sealed with a filling (Australian Dental Association, healthdirect). See fillings and root canal treatment.
  • Microabrasion, which the American Dental Association describes as removing a thin outer layer of enamel with an acidic, abrasive paste, for stains that do not go deeper than the enamel.
  • Veneers or crowns, which healthdirect lists as alternatives to whitening.

Whitening has limits. It does not work on crowns, veneers, dentures, implants or fillings (NHS, healthdirect), so these may end up a different colour from your natural teeth, as the American Dental Association notes. healthdirect says gel on the outside will not whiten teeth if the problem is deep inside them.

Is teeth whitening safe?

Side effects are common but usually short-lived. The NHS lists sensitivity to cold or sweet food and drink, sore gums or throat, and white patches on the gums. A 2018 Cochrane review of home whitening in adults found sensitivity and mouth irritation were the most common, more so with stronger products, but mild and temporary; it rated the evidence on how well home whitening works as low to very low certainty. healthdirect adds that strong gel can burn the lips, gums and tongue, is dangerous to swallow, and can cause pain or damage in cracked teeth.

The NHS says whitening is not done if you are 17 or younger or have unhealthy teeth or gums, and is not recommended if you are pregnant or breastfeeding. healthdirect adds sensitive teeth, gum disease, cracks or holes in the teeth, and untreated dental problems. See tooth sensitivity.

Home remedies: the sources differ. healthdirect says some research suggests baking soda, charcoal or fruits such as lemons and strawberries may help whiten teeth, but that using them often may damage your teeth. The American Dental Association is more doubtful: it says the limited studies raise questions about their effectiveness and safety, and that there is not enough evidence that charcoal products whiten teeth safely.

Who is allowed to whiten teeth?

The rules differ by country.

United Kingdom

The General Dental Council (GDC), which regulates UK dental professionals, says the law allows only registered dentists, or registered dental hygienists, dental therapists or clinical dental technicians working to a dentist's prescription, to provide whitening. Anyone else, such as a beautician, is breaking the law. The GDC's 2016 position statement on the regulations says:

  • products containing or releasing more than 6% hydrogen peroxide cannot be used for cosmetic whitening
  • products with 0.1% to 6% can only be supplied through a dental professional after an examination, the first use must be by the dental professional or under their direct supervision, and they cannot be used on anyone under 18 (except to treat or prevent disease)
  • products with less than 0.1%, such as toothpastes and mouth rinses, can be sold freely

The NHS says whitening at beauty salons, or with a kit from a pharmacy or online, does not work as well and may harm your teeth and gums. You can check whether someone is registered on the GDC website.

Australia

The Dental Board of Australia says only registered dental practitioners can use or supply high-concentration whitening products: over 6% hydrogen peroxide or over 18% carbamide peroxide. The Australian Dental Association explains that under the national Poisons Standard, products with 3 to 6% hydrogen peroxide or 9 to 18% carbamide peroxide can be sold directly to consumers if they carry required safety warnings. So the strength sold directly to the public can be higher in Australia (up to 6% hydrogen peroxide) than in the UK (under 0.1%). healthdirect warns that salon whitening and shop-bought kits can put you at risk of harm.

United States

The American Dental Association's policy is that the public should consult a licensed dentist about whether whitening is appropriate, and it urges state dental societies to support treating whitening by non-dentists (other than self-application, or a parent or guardian) as unlicensed dentistry. We did not find a national limit on whitening strength in the US sources we checked.

If you are thinking about whitening at home, our guides compare the at-home kits sold in Australia, the UK and EU and the United States, and explain whether whitening is safe.

When to see a dentist
  • A single tooth has turned darker, especially after a knock or injury.
  • Your teeth have changed colour and you do not know why.
  • Sensitivity or gum irritation after whitening lasts more than 1 or 2 days (healthdirect advice).
  • You are thinking about whitening and want your teeth and gums checked first.

How can you prevent stains?

healthdirect suggests cleaning your teeth every day with a toothbrush and floss, not smoking, and rinsing your mouth with water after food or drink that can stain. See how to brush your teeth, and raise any worries about colour at your dental check-up.

Frequently asked questions

Can I have my teeth whitened at a beauty salon?

In the UK, no: the General Dental Council says whitening by someone who is not a registered dental professional is a criminal offence. In Australia, healthdirect says salon whitening can put you at risk of harm, and only registered dental practitioners can use high-strength products.

Can one dark tooth be whitened?

Sometimes. The Australian Dental Association says stains inside a tooth can be very difficult to remove from the outside, and that internal bleaching is sometimes an option, for example after root canal treatment. A dentist needs to find the cause first.

Does whitening damage teeth?

The common side effects, sensitivity and mouth irritation, were mild and temporary in the 2018 Cochrane review. healthdirect warns that whitening can cause pain or further damage in cracked teeth, so have a dental check first.

Sources

  1. Teeth whitening, NHS, accessed September 2026
  2. Tooth whitening and illegal practice, General Dental Council, accessed September 2026
  3. Tooth whitening position statement, General Dental Council (July 2016), accessed September 2026
  4. Fluoride, Oral Health Foundation, accessed September 2026
  5. Teeth whitening, healthdirect Australia, accessed September 2026
  6. Teeth staining, Australian Dental Association, accessed September 2026
  7. Policy statement 2.2.8: teeth whitening (bleaching) by persons other than dental practitioners, Australian Dental Association, accessed September 2026
  8. Teeth whitening products, Dental Board of Australia, accessed September 2026
  9. Dental care: fluoride, Better Health Channel, accessed September 2026
  10. Whitening, American Dental Association, accessed September 2026
  11. Home-based chemical bleaching of teeth in adults, Cochrane (Eachempati and others, 2018), accessed September 2026

This article is general information about oral health. It is not a diagnosis or a substitute for advice from a dentist or doctor who knows your situation. If you have pain, swelling, bleeding that does not settle, or a problem that is getting worse, see a dental professional. In an emergency, contact your local emergency service.

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