Mouth ulcers are painful round or oval sores that form in the mouth, most often on the inside of the cheeks or lips.
They're usually white, red, yellow or grey in colour and are inflamed (red and swollen) around the edge.
Although mouth ulcers can be uncomfortable, especially when you eat, drink or brush your teeth, they are usually harmless.
Most mouth ulcers will clear up by themselves within a week or two. You only need to see your GP or dentist if the ulcer gets worse or lasts for longer than three weeks, or if you develop ulcers regularly.
How common are mouth ulcers?
Mouth ulcers are very common, particularly in women and young adults. Most people will have one or two a year.
However, some people have mouth ulcers that come back regularly. Recurrent mouth ulcers are estimated to affect about one in every five people in the UK.
What causes mouth ulcers?
Most minor, single mouth ulcers are caused by damage to the mouth, for example by accidentally biting the inside of your cheek while eating, or from a sharp tooth, food or filling.
The cause of a recurrent mouth ulcer is not always clear, but it's likely to be a combination of factors including a genetic vulnerability and a certain trigger. Possible triggers may include feeling stressed or anxious, eating certain foods, hormonal changes and stopping smoking.
In some cases, recurrent mouth ulcers are a sign of an underlying health condition, such as iron deficiency anaemia or Crohn's disease.
How to treat mouth ulcers
Most mouth ulcers heal within 10-14 days without causing any lasting problems, although severe ulcers may last for several weeks and could potentially leave a scar.
If you have a mouth ulcer that is particularly painful or is interfering with your daily activities (such as eating), some self-help measures and medications may help.
These can include using a soft toothbrush when brushing your teeth, avoiding hard and sharp foods, and using a mouthwash, spray, gel or lozenge to reduce the pain and help the ulcer heal faster.
Can mouth ulcers be prevented?
As the exact cause of most recurrent mouth ulcers is unknown, there is no certain way to prevent them. However, the following may help reduce your risk of developing mouth ulcers:
avoid damaging the inside of your mouth by using a soft toothbrush and avoiding hard, brittle or sharp-edged foods
avoid things you think may be triggering your ulcers, such as specific foods
learn some relaxation tips to relieve stress
make sure you maintain good oral hygiene, including brushing your teeth at least twice a day
have regular check-ups at your dentist – your dentist can spot and treat problems, such as sharp teeth or fillings, that could damage your mouth
eat a healthy, balanced diet rich in vitamins
Mouth ulcers are often uncomfortable but they usually clear up by themselves within a couple of weeks
Causes of mouth ulcers
Most minor, single mouth ulcers are caused by damage to the mouth, for example by accidentally biting the inside of your cheek while you are eating or from a sharp tooth, food or filling.
These ulcers will usually heal within a week or two and are not a sign of any serious problem.
Causes of recurrent mouth ulcers
The cause of mouth ulcers that keep coming back is not always clear. It is thought that your genes may make you more likely to develop mouth ulcers as a result of certain triggers, as around 40% of people who have recurrent mouth ulcers report that it runs in their family.
Some of the factors that may trigger recurrent mouth ulcers include:
stress and anxiety
hormonal changes – some women develop mouth ulcers during their monthly period
eating certain foods – such as chocolate, coffee, peanuts, almonds, strawberries, cheese, tomatoes and wheat flour
toothpaste additives – it has been suggested that the additive sodium lauryl sulphate, found in some toothpastes, may cause or aggravate mouth ulcers in some people
stopping smoking – when you first stop smoking, you may find you develop mouth ulcers (as a result of your body dealing with the change in chemicals in your body)
If you are trying to stop smoking, don't be put off if you develop mouth ulcers. Remember that the mouth ulcers are temporary, and the long-term health benefits of not smoking are far greater than the short-term discomfort of the ulcers. Read more about stopping smoking.
In some cases, recurrent mouth ulcers may be a sign of an underlying medical condition, such as:
viral infections – including the cold sore virus (herpes simplex),hand, foot and mouth disease and chickenpox
vitamin B12 deficiency – where a lack of vitamin B12 causes the body to produce abnormally large red blood cells that cannot function properly
iron deficiency – where a lack of iron in your blood leads to a reduction in the amount of oxygen reaching your organs and tissues
a common digestive condition where a person has an adverse reaction to gluten
a long-term condition that causes inflammation of the lining of the digestive system
a condition that causes inflammation in various places in the body, usually as a reaction to an infection
a non-infectious, itchy rash that can affect many areas of the body
a rare and poorly understood condition that causes inflammation of the blood vessels
immunodeficiency – when the body's immune system is attacked or suppressed, for example in HIV or lupus
Medications and treatments
Mouth ulcers can sometimes be caused by a medication you are taking or treatment you are having, such as:
such asibuprofen and aspirin
nicorandil – a medication sometimes used to treat angina
medicationsused to treat a variety of conditions that affect the heart and blood flow, such as angina, high blood pressure and abnormal heart rhythms
chemotherapy and radiotherapy – two common cancer treatments
You may notice that you start to get mouth ulcers when you begin your treatment, or when your dosage is increased.
Speak to your GP or care team if you think your treatment is causing your mouth ulcers. You may be able to take an alternative medication or you may be offered medication to treat the ulcers until you finish your course of treatment.
Could it be 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 they can appear elsewhere in the mouth.
You are more at risk of developing mouth cancer if you are male, over 45 years old and you smoke or drink heavily.
If mouth cancer is detected early, the chances of a complete recovery are good. This is why it is always important to have regular check-ups with your dentist. They can carry out a thorough assessment of your teeth and mouth, and will be able to spot any possible signs of mouth cancer.
Diagnosing mouth ulcers
If you have a mild mouth ulcer, there is usually no need for you to see your GP or dentist because these ulcers will usually heal within a week or two.
You only need to visit your GP or dentist if you have a mouth ulcer that is very painful or has lasted for more than three weeks, or if you are getting mouth ulcers regularly.
Seeing your GP or dentist
If you see your GP or dentist with a mouth ulcer, they will usually look inside your mouth to examine the ulcer first.
They may also ask some questions to help work out whether your mouth ulcers have an underlying cause or trigger. For example, you may be asked:
how often you get mouth ulcers
how long you've had your current ulcer
if you are aware of anyone in your family who has recurrent mouth ulcers
if you smoke
if you have any additional symptoms – such as weight loss, joint pain, a high temperature or ulcers on any other parts of your body (such as your skin or genitals)
In some cases, your GP or dentist might consider carrying out or referring you for a blood test. A sample of your blood can be tested to check for signs of infection or inflammation and to check your levels of iron and vitamin B12, which can sometimes help identify an underlying condition that could be responsible for your mouth ulcers.
Referral to a specialist
If you have had a severe mouth ulcer for more than three weeks, your GP or dentist may refer you to a hospital specialist.
You may also be referred if your mouth ulcer looks abnormal, for example if you have large red and white patches in your mouth that often bleed and are very painful.
The hospital specialist may decide to carry out a biopsy to help determine what may be causing your symptoms. This is a procedure in which a small tissue sample is taken from your mouth for further examination.
Treating mouth ulcers
Most mouth ulcers don't require specific treatment, as they will usually heal on their own within 10-14 days.
However, treatment may be necessary if your ulcers are severe, painful or interfere with your daily activities (such as eating).
If your mouth ulcers are thought to be the result of an underlying condition, you may need to be referred to a specialist so the condition can be treated.
If you have a mild mouth ulcer, there are some steps you can take yourself to help your ulcer heal more quickly:
Use a soft toothbrush when brushing your teeth.
Avoid hard, sharp, spicy and acidic foods and drinks until the ulcer heals – stick to soft foods that are easier to chew.
Avoid things that you think may be triggering your ulcers, such as specific foods. Read about the causes of mouth ulcers.
Reduce your stress levels by doing an activity that you find relaxing, such as yoga, meditation or exercise. Read more aboutrelaxation tips to avoid stress.
If your ulcer has a specific physical cause, such as a sharp tooth or filling cutting the inside of your cheek, it will usually heal naturally once the cause has been treated. If you suspect that a sharp tooth or filling has caused an ulcer, visit your dentist so that they can repair it.
If necessary, your GP or dentist can prescribe medication that may help ease your symptoms.
Some mouth ulcer treatments can also be bought without a prescription from your local pharmacy, although you should speak to your pharmacist about which medicine may be best for you. Some treatments aren't suitable for children or for women who are pregnant, breastfeeding or trying to get pregnant.
The main treatments for mouth ulcers are described below, although the evidence supporting their use is limited. These treatments also won't stop you developing new mouth ulcers in the future.
Corticosteroids are a type of medication that reduces inflammation. They can help reduce pain associated with mouth ulcers and help them heal faster.
Corticosteroids are available in many different forms, including mouthwashes and sprays.
You should speak to your GP for advice before using corticosteroid medications for mouth ulcers in children under 12 years old.
Antimicrobial mouthwash helps kill bacteria, viruses or fungi that could infect the ulcer, particularly if a painful mouth ulcer means you are unable to brush your teeth properly. They may also help speed up healing.
Chlorhexidine gluconate is the most commonly prescribed mouthwash, although various gels and sprays are also available.
Chlorhexidine gluconate is normally used twice a day. After using chlorhexidine gluconate, you may notice that your teeth are covered in a brown stain. This staining is not permanent, and your teeth should return to their normal colour once you finish the treatment.
The best way to prevent staining is to brush your teeth before using chlorhexidine gluconate mouthwash. However, after brushing your teeth make sure that you thoroughly rinse your mouth out with water before using the mouthwash.
Chlorhexidine gluconate mouthwash should not be used by infants under two years old.
If your mouth ulcer is very painful, your GP may prescribe a painkiller that you can apply directly to your ulcer. These are available as mouthwashes, sprays, lozenges and gels.
Your GP will usually prescribe benzydamine, which is available as a mouthwash or spray. However, the mouthwash is not suitable for children under 12 years of age and shouldn't usually be used for more than seven days in a row.
Benzydamine mouthwashes and sprays may also sting when you first use them, but this should lessen as you continue to use them. You may find it useful to dilute the mouthwash with an equal amount of water before using it if stinging is a problem. If the stinging persists, your pharmacist or GP may recommend stopping treatment.
You may also find that your mouth feels numb when you first use enzydamine mouthwashes and sprays. This is normal and the feeling will soon return to your mouth.