Introduction 

Mouth ulcers are painful sores that appear in the mouth. Although they're uncomfortable, they’re usually harmless and most clear up by themselves within a week or two.

Mouth ulcers are common and can usually be managed at home, without seeing your dentist or GP. Visit your pharmacist first, unless your ulcer has lasted longer than three weeks.

What does a mouth ulcer look like?

Mouth ulcers are usually round or oval sores that commonly appear inside the mouth on the:

  • cheeks
  • lips
  • tongue

They can be white, red, yellow or grey in colour and swollen.

It's possible to have more than one mouth ulcer at a time and they may spread or grow.

Mouth ulcers shouldn't be confused with cold sores, which are small blisters that develop on the lips or around the mouth. Cold sores often begin with a tingling, itching or burning sensation around your mouth.

When to see your pharmacist, dentist or GP

Mouth ulcers can be painful, which can make it uncomfortable to eat, drink or brush your teeth.

It's usually safe to treat mouth ulcers at home. See your GP or dentist if:

  • your mouth ulcer has lasted three weeks
  • you keep getting mouth ulcers
  • your mouth ulcer becomes more painful or red – this could be a sign of a bacterial infection, which may need treatment with antibiotics

Mouth ulcers are also a possible symptom of a viral infection that mainly affects young children, called hand, foot and mouth disease. Speak to your GP or call NHS 111 if you're unsure.

Read about the symptoms of hand, foot and mouth disease.

How to treat mouth ulcers

Mouth ulcers don’t usually need to be treated, because they tend to clear up by themselves within a week or two.

However, treatment can help to reduce swelling and ease any discomfort. This may help if you keep getting mouth ulcers or your mouth ulcer affects eating and drinking.

Self care

Things you can do to speed up healing include:

  • applying a protective paste recommended by your pharmacist
  • using a soft toothbrush to brush your teeth
  • using a toothpaste that doesn’t contain sodium lauryl sulphate, as this may be irritating 
  • avoiding hard, spicy, salty, acidic or hot food and drink until the ulcer heals
  • using a straw to drink cool drinks
  • avoiding things that may be triggering your mouth ulcers – see causes, below

Pharmacy medicines

You can buy several types of mouth ulcer treatment from a pharmacy. Speak to your pharmacist about the best treatment for you. Options include the following:

  • Antimicrobial mouthwash may speed up healing and prevent infection of the ulcer. Children under two shouldn't use this treatment. It also contains chlorexidine gluconate, which may stain teeth – but this may fade once treatment is finished. 
  • Painkillers are available as a mouthwash, lozenge, gel or spray. They can sting on first use and your mouth may feel numb – but this is temporary. Mouthwash can be diluted with water if stinging continues. Children under 12 shouldn’t use mouthwash or gel. Mouthwash shouldn’t be used for more than seven days in a row.
  • Corticosteroid lozenges may reduce pain and speed up healing. These are best used as soon as the ulcer appears, but shouldn't be used by children under 12.

Medicines from your dentist or GP

If necessary, you may be prescribed a course of stronger corticosteroids to help reduce pain and swelling, and speed up healing.

Corticosteroids are available on prescription as tablets, mouthwash, paste or spray, but are not suitable for children under 12.

Is it mouth cancer?

In a few cases, a long-lasting mouth ulcer can be a sign of mouth cancer. Ulcers caused by mouth cancer usually appear on or under the tongue, although you can get them in other areas of the mouth.

Risk factors for mouth cancer include:

  • smoking or using products that contain tobacco
  • drinking alcohol – smokers who are also heavy drinkers have a much higher risk compared to the population at large
  • infection with the human papilloma virus (HPV) – the virus that causes genital warts

It's important to detect mouth cancer as early as possible. If mouth cancer is detected early, the chances of a complete recovery are good. Regular dental check-ups are the best way to detect the early signs.

What causes mouth ulcers?

In many cases, the reason for mouth ulcers is unclear. Most single mouth ulcers are caused by damage to the lining inside of the mouth. For example:

  • accidentally biting the inside of your cheek or a sharp tooth
  • poorly fitting dentures
  • hard food
  • a defective filling

It’s not always clear what causes mouth ulcers that keep returning, but triggers are thought to include:

  • stress and anxiety 
  • hormonal changes – some women develop mouth ulcers during their monthly period
  • eating certain foods – such as chocolate, spicy foods, coffee, peanuts, almonds, strawberries, cheese, tomatoes and wheat flour
  • toothpaste containing sodium lauryl sulphate
  • stopping smoking – when you first stop smoking, you may develop mouth ulcers

Your genes are also thought to have a role – around 40% of people who keep getting mouth ulcers report that it runs in their family.

Medical conditions

Mouth ulcers can sometimes be caused by certain medical conditions, such as:

Medications and treatments

Mouth ulcers can sometimes be caused by certain medications or treatments, such as:

Can mouth ulcers be prevented?

It may not be possible to prevent mouth ulcers, because they're often caused by things you can't control (such as a family history or a medical condition).

However, the following may help to reduce your risk of developing mouth ulcers:

  • avoiding certain foods – such as chocolate, spicy foods, coffee, peanuts, almonds, strawberries, cheese, tomatoes and wheat flour, if they cause you to have an ulcer
  • not chewing gum
  • brushing your teeth with a soft-bristled brush, which may reduce irritation in your mouth
  • using toothpaste that doesn’t contain sodium lauryl sulphate
  • reducing stress and anxiety – which may be a trigger for some people

Read more advice on dental health




Page last reviewed: 15/03/2016

Next review due: 15/03/2018