Oral Health›Common problems

White and Red Patches in the Mouth: Causes and When to Get Checked

White or red patches in the mouth have many causes, from thrush and cheek biting to leukoplakia. Most are not cancer, but a patch that does not rub off or go away should be checked. Here is what the common causes are and what happens next.

Updated September 2026·By the OHA editorial team·8 min read·How we write
Key takeaways
  • A white patch that cannot be rubbed away is called leukoplakia; a red patch is called erythroplakia. Neither is cancer, but a small number can change into cancer over time, so they need checking.
  • Many patches have other causes. Thrush usually rubs off, lichen planus often has a lace-like pattern, and rubbing from a sharp tooth, a denture or cheek biting can cause white patches that go when the cause is removed.
  • Smoking, chewing tobacco, betel nut or paan, and alcohol are the main risk factors for leukoplakia.
  • See a dentist or GP about a white or red patch that does not go away. A dentist may take a small sample (a biopsy) to find out what it is.
  • Many patches need no treatment beyond stopping smoking, cutting down on alcohol and regular check-ups. Some are removed.

A white or red patch inside the mouth can be worrying, but most are not cancer. The NHS says a white tongue can be a sign of several conditions, including lichen planus, leukoplakia, geographic tongue, mouth ulcers and oral thrush, and advises against diagnosing yourself. This guide explains the common causes and why a patch that lasts should be checked.

What are leukoplakia and erythroplakia?

Leukoplakia is a white patch in the mouth. The NHS says the patches are not usually painful, are an irregular shape, may be slightly raised or have red areas within them, and cannot be rubbed or scraped away. They often appear on or below the tongue, and can also form inside the cheeks, on the gums, or on the floor or roof of the mouth.

Erythroplakia is a red area in the mouth that bleeds easily, and erythroleukoplakia is an area of red and white patches (Cancer Research UK).

Cancer Research UK explains that these patches may be harmless, but can contain abnormal cells called dysplasia, which is not cancer but might develop into cancer if untreated. It says precancerous changes are more common in red patches than white ones, and most leukoplakia patches are not precancerous. The NHS says there is a small chance leukoplakia could progress to mouth cancer over time, which is why it should be checked.

Hairy leukoplakia is different: the NHS says it is caused by a virus, affects people with a weakened immune system, and does not carry a risk of mouth cancer. See HIV and oral health.

Other causes of white patches

Oral thrush

Thrush is a fungal infection. The NHS describes a mouth that is red inside with white patches, which leave red spots that can bleed when wiped off. Cancer Research UK says that if the patches go away with antifungal treatment, they are not related to cancer. See oral thrush.

Lichen planus

The NHS says lichen planus can cause white patches on the gums, tongue or inside the cheeks, with burning or stinging when you eat or drink. A Cambridge University Hospitals leaflet describes a lace-like pattern of streaky white patches, often the same on both sides of the mouth, sometimes with red patches or sores. See oral lichen planus.

Rubbing, sharp teeth and cheek biting

A Royal Berkshire NHS Foundation Trust leaflet explains that constant rubbing can cause harmless white patches, called frictional keratosis, which form like calluses on the hands. Common causes are biting the cheek or lips, ill-fitting dentures, jagged teeth, poorly fitting fillings or crowns, and brushing too hard. Most people have no symptoms. It is treated by removing the cause, such as correcting the denture or tooth. The leaflet adds that white patches linked to smoking can be hard to tell apart from it, so the cause needs to be identified.

Red patches

Thrush and lichen planus can also cause red areas. Red, map-like patches on the tongue may be geographic tongue, which the Australian Dental Association describes as harmless, but it advises having this confirmed by a dentist, because other conditions, including oral cancer, can cause red patches. See tongue problems.

What raises the risk of leukoplakia?

  • Tobacco. The NHS says smoking and chewing tobacco are thought to increase your chances of leukoplakia, and advises not chewing tobacco, paan or betel nuts. DermNet also links it with betel quid chewing.
  • Alcohol (Cancer Research UK, DermNet).
  • Dentures that rub, and long-term mouth infections such as thrush (Cancer Research UK).

The sources put the cause differently. NHS 111 Wales says that in the UK leukoplakia is mostly caused by smoking. Cancer Research UK says that in most cases the cause is unknown, and the NHS says the exact cause is not known. See smoking, vaping and oral health and alcohol and oral health.

Why a patch that does not go away needs checking

A red or white patch is one of the signs of mouth cancer listed by the NHS, healthdirect Australia, the Australian Dental Association and the US National Institute of Dental and Craniofacial Research (NIDCR). The NHS says these symptoms are very common and can have other causes, but finding cancer early may make it easier to treat. The Australian Dental Association says mouth cancer often causes no symptoms at first, so a painless patch still needs checking.

How long to wait differs by country

  • UK: the NHS (England) says see a dentist or GP if you have a white patch that does not go away, and lists a red or white patch among the reasons to see a GP, without giving a waiting time. NHS 111 Wales says see a dentist or GP about a white patch that has not gone away after 2 weeks. NICE guidance for health professionals says to consider an urgent referral to a dentist for a red, or red and white, patch.
  • Australia: healthdirect says see your doctor or dentist if you have any symptoms of mouth cancer, notice any changes in your mouth, or are unsure whether something is normal.
  • US: the NIDCR says see a dentist or doctor about a white or red patch that lasts more than two weeks.

These timescales are the point to stop waiting, not a reason to delay. For ulcers and lumps, see mouth cancer and lumps and bumps in the mouth.

What happens at the appointment?

The NHS says the dentist or GP will look at the patch and rule out other causes, such as thrush or cheek biting. DermNet says it can be appropriate to wait two weeks to see whether a patch improves with first steps, such as treating thrush, changing tooth brushing habits or stopping smoking.

You may be referred to a specialist for a biopsy, where a small piece of the patch is removed and checked for abnormal cells (NHS). Leaflets from Newcastle and Cambridge NHS hospitals say this is usually done under local anaesthetic, which numbs the area, and takes around 15 to 30 minutes. Results are usually given at a follow-up appointment or by letter.

How are patches treated?

The NHS says treatment for leukoplakia is not always needed, but you will have regular check-ups to make sure the patch is not getting bigger. The patch may get smaller or go away if you stop smoking, stop or cut down on alcohol, and do not chew tobacco, paan or betel nuts. The American Dental Association's MouthHealthy site says treatment begins with removing contributing factors, such as tobacco or ill-fitting dentures.

Cancer Research UK says patches with no dysplasia or mild dysplasia might not need treatment, but are checked regularly, sometimes for many years. If there is dysplasia, surgery or laser treatment may be suggested to remove the patch. The NHS says the mouth should heal quickly afterwards.

When to see a dentist or GP
  • You have a white patch that does not rub off, or a red patch, that has not gone away (NHS). Welsh and US guidance give 2 weeks as the point to stop waiting.
  • A patch has changed or grown, or you have pain or discomfort in your mouth that is not going away (NHS).
  • You have white patches and a weakened immune system (NHS).
  • Thrush has not improved after 1 week of treatment with a mouth gel: see a GP (NHS).
  • A denture, sharp tooth or filling is rubbing the inside of your mouth.
  • You have been told you have leukoplakia or lichen planus: keep up your regular check-ups.

Frequently asked questions

Is a white patch in my mouth cancer?

Usually not. Cancer Research UK says most leukoplakia patches are not precancerous, and many patches are caused by thrush, lichen planus or rubbing. But a patch that does not go away should be checked, because a small number can change over time.

How can I tell if a white patch is thrush?

Thrush patches usually rub off, leaving a sore red area underneath (NHS, Cancer Research UK). Leukoplakia cannot be rubbed away. A pharmacist can advise on thrush, but see a dentist or GP if a patch does not rub off or clear.

Will stopping smoking make a patch go away?

It may. The NHS says a leukoplakia patch may get smaller or go away if you stop smoking, cut down on alcohol and stop chewing tobacco, paan or betel nuts, and that these steps may also reduce your risk of mouth cancer.

Sources

  1. Leukoplakia, NHS, accessed September 2026
  2. Sore or white tongue, NHS, accessed September 2026
  3. Oral thrush (mouth thrush), NHS, accessed September 2026
  4. Lichen planus, NHS, accessed September 2026
  5. Symptoms of mouth cancer, NHS, accessed September 2026
  6. Leukoplakia, NHS 111 Wales, accessed September 2026
  7. Suspected cancer: recognition and referral (NG12), recommendations organised by site of cancer, NICE, accessed September 2026
  8. Precancerous changes in the mouth and oropharynx, Cancer Research UK, accessed September 2026
  9. Symptoms of mouth and oropharyngeal cancer, Cancer Research UK, accessed September 2026
  10. Oral frictional hyperkeratosis (FK) (leaflet), Royal Berkshire NHS Foundation Trust, accessed September 2026
  11. Lichen planus of the mouth, Cambridge University Hospitals NHS Foundation Trust, accessed September 2026
  12. Oral (mouth) biopsy, Cambridge University Hospitals NHS Foundation Trust, accessed September 2026
  13. Oral (mouth) biopsy information leaflet for patients, Newcastle Hospitals NHS Foundation Trust, accessed September 2026
  14. Oral leukoplakia, DermNet, accessed September 2026
  15. Leukoplakia, American Dental Association (MouthHealthy), accessed September 2026
  16. Mouth cancer, healthdirect Australia, accessed September 2026
  17. Oral cancer, Australian Dental Association, accessed September 2026
  18. What are these red patches on my tongue?, Australian Dental Association, accessed September 2026
  19. Oral cancer, NIH National Institute of Dental and Craniofacial Research, 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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