Dr Nazem Al IoussefGeneral Dentist · Dubai

Patient guide

Mouth ulcers

Mouth ulcers are small, painful sores on the inside of the mouth. They are common and not contagious, and most clear up on their own within a week or two. This guide explains what sets them off, what makes them easier to live with while they heal, and which signs mean an ulcer should be looked at.

From the professional website of Dr Nazem Al IoussefPublished Last reviewed

What a mouth ulcer looks like

A typical mouth ulcer is a small round or oval sore, often about the size of a pencil tip. The centre is white, yellow or grey, with a red edge around it. Ulcers usually form on the soft parts of the mouth: the inside of the cheeks and lips, the tongue and sometimes the gums. There may be one or several at a time, and they can sting when you eat, drink or brush.

The common, recurring kind is called an aphthous ulcer, or in the United States a canker sore. Cold sores are different: they form on the lips or around the mouth.

A mouth ulcer and how long it usually lasts

  1. A typical ulcer. A small round sore on the inside of the lower lip, with a pale centre and a red edge.
  2. How long it lasts. Most mouth ulcers clear up on their own within a week or two. One that lasts longer than three weeks should be checked by a dentist or doctor.

Simplified drawing, not to scale.

Why they appear

A single ulcer is usually caused by something you can try to avoid:

  • biting the inside of your cheek;
  • a sharp tooth, a rough filling, or a denture or brace that rubs;
  • a cut or burn from hard food or a hot drink;
  • brushing too hard, or a toothpaste that irritates the mouth;
  • a food intolerance or allergy;
  • feeling tired, stressed or anxious.

An ulcer from an injury like these usually heals once the cause is removed. Other triggers are harder to control:

  • hormonal changes, for example during pregnancy;
  • your genes, since some families get mouth ulcers more often;
  • a shortage of iron, zinc, folic acid, B vitamins or vitamin D;
  • some medicines, including certain anti-inflammatory painkillers (NSAIDs), beta blockers and nicorandil;
  • stopping smoking, as some people develop ulcers when they first give up.

Some otherwise healthy people get ulcers again and again. This is called recurrent aphthous stomatitis. It is most common in children, teenagers and young adults, and the immune system is thought to play a part, but the exact cause is not known.

When ulcers point to something else

Now and then, several ulcers at once, or ulcers that keep coming back, are linked to another condition, such as:

  • hand, foot and mouth disease, which also causes a rash on the hands and feet;
  • a herpes simplex infection, which is more common in children;
  • oral lichen planus, which leaves a white, lacy pattern inside the cheeks;
  • anaemia or a shortage of vitamins;
  • digestive conditions such as Crohn's disease and coeliac disease;
  • conditions that weaken the immune system.

This is why a dentist or doctor may ask about your general health, and sometimes arrange a blood test.

What helps while it heals

A mouth ulcer needs time to heal, and there is no quick fix. Keeping away from whatever irritates it can ease the pain and give it the chance to settle.

  1. Brush gently. Use a soft-bristled toothbrush and keep cleaning twice a day, taking care around the sore. The guide to cleaning your teeth explains how.

  2. Choose softer food. Very spicy, salty or acidic food, and rough, crunchy food such as toast or crisps, tend to sting.

  3. Keep drinks cool. Very hot drinks and acidic ones such as fruit juice can irritate the ulcer. A straw keeps cool drinks off it.

  4. Check the toothpaste. The NHS advises against toothpaste containing sodium lauryl sulfate (SLS), a foaming agent, if you have mouth ulcers. If you switch, choose one that still contains fluoride.

  5. Rinse with salt water. Dissolve half a teaspoon of salt in a glass of warm water, rinse, and spit it out without swallowing.

A pharmacist can suggest something to reduce pain or help prevent infection, such as an antimicrobial mouthwash, a pain-relieving gel, spray or tablet, or corticosteroid lozenges. Which of these need a prescription differs from country to country, so ask the pharmacist and follow the instructions on the pack.

When to see a dentist or doctor

Most mouth ulcers are harmless. See a dentist or doctor if an ulcer:

  • lasts longer than three weeks;
  • is different from ulcers you have had before, for example bigger than usual or near the back of the throat;
  • bleeds, or becomes more painful and red, which can be a sign of infection;
  • is very painful or keeps getting worse.

Seek advice too if ulcers keep coming back, or if you feel unwell or have other symptoms, such as ulcers elsewhere on the body or painful, red or swollen joints.

Mouth ulcers are rarely a sign of anything serious. The three-week point matters because an ulcer that does not heal is sometimes a sign of mouth cancer. More common conditions can look the same, so a lasting ulcer does not mean cancer, but it should be checked, as should a red or white patch or a lump in the mouth.

What a dentist or doctor may do

They will look at the ulcer and ask about your symptoms and general health. Depending on what they find, they may:

  • smooth a sharp tooth or rough filling, or adjust a denture that rubs;
  • prescribe a stronger medicine for severe, lasting or infected ulcers, such as a steroid spray or tablets, a pain-relieving gel, or a mouthwash that kills germs;
  • arrange a blood test for a shortage of iron or vitamins;
  • refer you for further tests if an ulcer has not healed or looks unusual.

Questions patients ask

Are mouth ulcers contagious?

No. A mouth ulcer cannot be passed on by kissing or by sharing cups, cutlery or food. Cold sores are a different condition: they appear on the lips or around the mouth and often start with tingling, itching or burning.

Why do I keep getting mouth ulcers?

Some otherwise healthy people get them again and again, and the exact cause is not known. Noting when each ulcer appears, with what you had eaten, the toothpaste you used and how stressed you were, may show a pattern. If they keep coming back, see a dentist or doctor, who may look for a shortage of iron or vitamins or for another condition.

Should I change my toothpaste?

It may help. The NHS advises people with mouth ulcers to avoid toothpaste containing sodium lauryl sulfate (SLS), and for some people a toothpaste without it means fewer ulcers. Choose one that still contains fluoride.

Can children get mouth ulcers?

Yes. The recurring kind is most common in children, teenagers and young adults. Several ulcers at once, with a rash on the hands and feet or with feeling unwell, can come from a viral infection such as hand, foot and mouth disease. A child who is unwell with mouth ulcers should see a doctor.

Is a mouth ulcer a sign of cancer?

Rarely. An ulcer that lasts longer than three weeks is sometimes a sign of mouth cancer, so it should be checked by a dentist or doctor. Having one does not mean you have cancer: other, common conditions cause the same sign.

What this page rests on

This guide rests on patient information from the NHS, the Oral Health Foundation, the American Dental Association and the American Academy of Oral Medicine. The healing times and the three-week advice are the NHS's. It is general information: the cause of a particular ulcer can only be found by a dentist or doctor who examines it.

General health information, not a diagnosis or a treatment recommendation for any individual.

Sources

  1. NHS — Mouth ulcers
  2. NHS — Symptoms of mouth cancer
  3. Oral Health Foundation — Mouth ulcers
  4. American Dental Association, MouthHealthy — Canker sores
  5. American Academy of Oral Medicine — Canker sores

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