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Mouth Ulcers

Mouth ulcers are painful, clearly defined, round or oval sores that form in the mouth. They are sometimes also known as aphthous ulcers.

Mouth ulcers are painful, clearly defined, round or oval sores that form in the mouth. They are sometimes also known as aphthous ulcers.

Types of mouth ulcer

There are three main types of mouth ulcer:

  • Minor ulcers are the most common type, accounting for 80% of all cases. They are small (2-8mm in diameter) and usually heal naturally, within 10-14 days. A minor ulcer will not cause any scarring.
  • Major ulcers are deeper and larger than minor ulcers, and usually have a raised or irregular border. They are usually 1cm or more in diameter. Major ulcers take longer to heal (several weeks) and can cause scarring.
  • Herpetiform ulcers form as multiple, pinhead-sized sores. The number of ulcers can range from five to 100. These tiny ulcers often fuse together to form larger, irregular shaped sores, which are very painful. Around 5-10% of mouth ulcers are herpetiform. Herpetiform ulcers are not related to the herpes virus.

How common are mouth ulcers?

Mouth ulcers are very common. Most people will have at least one during their lifetime. They affect at least 20% of the population. Studies have shown that mouth ulcers are more common in women.

Mouth ulcers are more common in young adults.

Mouth ulcers cannot be passed from person to person. For example, you cannot get an ulcer from kissing someone or from sharing drinking glasses or cutlery.

Recurrent mouth ulcers

Most people only have mouth ulcers occasionally. However, some people develop mouth ulcers on a recurring or frequent basis. In general, one person in five will have recurrent mouth ulcers. About 5-10% of children can have recurrent mouth ulcers.

The factors that cause recurrent mouth ulcers are often different from those that cause single ulcers. See Mouth Ulcers-causesfor more information.

Mouth ulcers are easily identifiable by their appearance. A mouth ulcer will be:

  • round or oval in shape
  • white, yellow or grey in colour
  • inflamed around the edge

Most mouth ulcers usually occur on:

  • the inside of the lips
  • the inside of the cheeks
  • the floor of the mouth
  • the under surface of the tongue

It is rare to get a mouth ulcer on the roof of your mouth.
A mouth ulcer can cause pain and discomfort, particularly when eating, drinking or brushing your teeth.

Most mouth ulcers only last 10 to 14 days, although they may last for several weeks in more severe cases.

When to see your GP

Visit your GP if you have a mouth ulcer that:

  • gets progressively more painful and inflamed
  • lasts for more than three weeks

Also visit your GP if you develop an ulcer somewhere else on your body, such as your genitals.

In most cases, mouth ulcers are not caused by an infection. This means they cannot be passed from person to person. For example, in most cases it is not possible to get a mouth ulcer from kissing someone who has a mouth ulcer, or by sharing drinking glasses or cutlery with them.
Most minor, single mouth ulcers are caused by damage to the mouth. For example, you may damage the inside of your mouth by accidentally biting the inside of your cheek while you are eating. Mouth damage can also occur from using a toothbrush incorrectly, or from a sharp tooth or filling.

Recurrent mouth ulcers

The cause of recurrent (returning) mouth ulcers is often unknown. However, a number of factors may increase your chances of getting recurrent ulcers. These are listed below.

  • Stress and anxiety
  • Oral trauma, such as excessive tooth brushing, or chewing sharp or hard foods.
  • Hormonal changes: some women develop mouth ulcers during their period. This is due to changes in the hormone levels in your body during your menstrual cycle.

Eating certain foods can also increases your likelihood of developing mouth ulcers. Foods that have been identified as increasing the risk of mouth ulcers include:

  • chocolate
  • coffee
  • peanuts
  • almonds
  • strawberries
  • cheese
  • tomatoes
  • wheat flour

Around 40% of people who have recurrent mouth ulcers have a family history of the condition. 

Stopping smoking

When you first stop smoking, you may find that you develop more mouth ulcers than usual. This is a normal reaction. Your body is dealing with the change in chemicals in your body.

After giving up smoking, any increase in mouth ulcers will be temporary, and you should not let it deter you from stopping smoking. The long-term health benefits of not smoking are far greater than the short-term discomfort of mouth ulcers.
Not smoking will significantly lower your risk of developing serious smoking-related conditions, such as heart disease and lung cancer. Your overall level of fitness will also improve greatly.

Underlying conditions

If you have recurrent mouth ulcers, they may be caused by an underlying medical condition, such as those outlined below.

  • Vitamin B12 deficiency: vitamin B12 helps to make red blood cells and keeps your body's nervous system healthy. A lack of vitamin B12 can cause tiredness, shortness of breath and mouth ulcers.
  • Iron deficiency: if your diet is lacking in iron, your red blood cells will not be able to carry as much oxygen. This can make you feel tired, lethargic (lacking energy) and dizzy. Sometimes, an iron deficiency can also cause mouth ulcers.
  • Coeliac disease is caused by intolerance to a protein called gluten, which is found in wheat, rye and barley. The condition causes the small intestine to become inflamed. Mouth ulcers are also a common symptom in adults with the coeliac disease.
  • Crohn's disease is a condition that causes inflammation of the gut, leading to ulcers developing in both your stomach and mouth.
  • Reactive arthritis is a reaction to another infection within your body. It can cause inflammation, which sometimes spreads to your mouth.
  • Immunodeficiency: any condition that attacks or suppresses the body's immune system (the body's natural defence against infection and illness) can cause you to develop mouth ulcers. For example, HIV is an immunosuppressant illness.


Occasionally, mouth ulcers are caused by a reaction to a medicine that you are taking. Some of the medicines that can cause mouth ulcers are listed below.

  • Non-steroidal anti-inflammatory drugs (NSAIDs): painkilling medication, such as ibuprofen and aspirin. Children who are under 16 years of age should not be given aspirin.
  • Nicorandil is sometimes used to treat angina (chest pain caused by reduced blood flow to the heart).
  • Beta-blockers are used to treat a variety of conditions that affect the heart and blood flow, such as angina, heart failure, high blood pressure and abnormal heart rhythms.

You may notice that you start to get mouth ulcers when you begin taking the medicine, or when you increase the dosage. However, this is often only a temporary effect of the medication.

Speak to your GP if you find that you are having more mouth ulcers as a result of your medication. They may be able to prescribe an alternative medicine for you. However, never stop taking medication that has been prescribed for you unless your GP advises you to do so.

Less common causes

There are also a number of other, less common causes of mouth ulcers. Some of these are listed below:

  • Herpes simplex infection: a highly contagious virus, also known as the 'cold sore virus', which can cause cold sores on the mouth and the genitals.
  • Anaemia: a condition that occurs when there is a reduced number of red blood cells or lower concentrations of haemoglobin (a protein found in red blood cells that transports oxygen around the body). Mouth ulcers can also be caused by other blood disorders, although this is rare.
  • Iron deficiency, vitamin B12 deficiency or folate deficiency.
  • Skin conditions, such as lichen planus (where flat, blue or violet colour skin lesions appear on the skin), and angina bullosa haemorrhagica (blood-filled blisters that turn to ulcers if they burst).
  • Gastrointestinal disease: for example, irritable bowel syndrome (IBS) and gastro-oesophageal reflux disease (GORD).
  • Pharyngitis: a sore throat.
  • Chickenpox: a mild but highly infectious condition that causes an itchy rash, which blisters and becomes crusty.
  • Hand, foot and mouth disease: a common, mild illness that is caused by a type of virus known as an enterovirus.
  • A reaction to prescribed medication.

Less common bacterial and viral infections can also sometimes cause mouth ulcers, although this is rare.

If you have a mild mouth ulcer, there is no need for you to have a formal diagnosis from your GP. You will also not require any specific treatment, but there are some self-care tips that you can follow to help the ulcer heal faster.

Visit your GP if you have a mouth ulcer that is causing significant pain, or if you are getting mouth ulcers on a recurrent basis. Also visit your GP if your mouth ulcer has lasted for more than three weeks.

Your GP may look inside your mouth to examine your mouth ulcer. They will also look at your medical history to help them work out what is causing your ulcer.

Recurring ulcers

If you have recurrent mouth ulcers (ulcers that keep coming back), your GP may ask you a series of questions to help determine whether your mouth ulcers have an underlying cause. For example, they may ask you about:

  • the frequency of your ulcers (how often they occur)
  • how long your ulcers last for
  • how severe the pain is
  • what treatments you have used - either prescribed or over the counter

If your GP is unsure about the diagnosis, they might want to rule out any conditions that could be causing your ulcers to keep recurring. They may refer you for a series of blood tests. The tests that you have may include those outlined below.

  • Full blood count (FBC). This is a common type of blood test that indicates the state of your general health. It will show whether there is an infection in your body, and will also indicate whether you have been exposed to any toxic substances.
  • Erythrocyte sedimentation rate (ESR). This test will not confirm a specific condition but it will show whether there is inflammation in your body. If there is inflammation, your GP can conduct further tests to help determine what condition may be causing it.
  • Ferritin. This test measures how much iron is being stored in your body. A lack of iron in your body can cause recurrent mouth ulcers.
  • Vitamin B12. This test checks whether you have enough vitamin B12 in your body. A lack of vitamin B12 can also cause recurrent mouth ulcers.


If you have had a severe mouth ulcer for more than three weeks, your GP may to refer you to a specialist. You may require a biopsy (a procedure in which a small tissue sample is taken for further examination) to help determine the cause of your ulcer.

You will also be referred to a specialist if your mouth ulcers are abnormal in appearance. For example, some people develop large red and white patches in their mouth, which often bleed and are painful. If this is the case, you may be referred for further examination.

Mouth cancer

It is very important to visit your GP if your ulcer has lasted for more than three weeks or it appears abnormal. For example, if it is made up of large red and white patches that often bleed.

This is because a severe, long-lasting mouth ulcer can be a sign of mouth cancer. For example, about 80% of people with mouth cancer have a long-lasting mouth ulcer that does not heal.
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
  • a heavy smoker
  • a heavy alcohol drinker

If mouth cancer is detected at an early stage, 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.

Most mouth ulcers do not require specific treatment. They will usually heal naturally without the need for treatment if they are:

  • infrequent
  • mild
  • do not interfere with your daily activities, such as eating


If you have a mild mouth ulcer, there is some self-care advice that you can follow, which may help your ulcer to heal more quickly. You should:

  • use a soft toothbrush when brushing your teeth
  • avoid eating hard foods, such as toast, and stick to soft foods that are easier to chew
  • avoid eating foods that have been known to cause ulcers in the past, until the ulcer has completely healed
  • reduce your stress levels by doing an activity that you find relaxing, such as yoga, meditation or exercise

If your ulcer has a specific cause, such as a sharp tooth, it will usually heal naturally once the cause has been treated. If you suspect that a sharp tooth has caused an ulcer, visit your dentist so that they can repair it.

The following have shown to be related to recurrent mouth ulcers in the past:

  • flavouring agents
  • essential oils
  • cinnamon
  • gluten
  • cow's milk
  • coffee
  • chocolate
  • potatoes
  • figs
  • cheese
  • nuts
  • citrus fruits
  • certain spices


If your ulcer is causing you significant pain and discomfort, your GP will prescribe a medication to help ease your symptoms.

If you prefer, many of the medicines that are used to treat ulcers can also be purchased over the counter at your local pharmacy. Speak to your pharmacist about which medicine would be most suitable for you. Some mouth ulcer gels are not suitable for children under 16.

Some of the various medicines used to treat mouth ulcers are outlined below.

Antimicrobial mouthwash

Antimicrobial mouthwash helps to kill any micro-organisms, such as bacteria, viruses or fungi that may cause a mouth infection if you are unable to brush your teeth properly.

Chlorhexidine gluconate is the most commonly prescribed mouthwash. You normally have to use it twice a day.

After using chorhexidine 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 chorhexidine gluconate mouthwash. However, after brushing your teeth make sure that you thoroughly rinse your mouth out with water before using the mouthwash.

Chorhexidine gluconate mouthwash should not be used by infants under two years old.


A corticosteroid is a type of medicine that reduce inflammation (swelling). Mouth ulcer medications contain a low dose of corticosteroid, which is usually enough to lower the inflammation.

Reducing the inflammation of your ulcer will make it is less painful. It is best to start using corticosteroid medication as soon as a mouth ulcer develops.

Hydrocortisone is the most commonly prescribed corticosteroid. It comes in the form of a lozenge, which slowly dissolves in your mouth. You usually have to take a lozenge four times a day.
Children under 12 years old should see a GP before starting this treatment. Your GP will inform you how to use this medication.


If your mouth ulcer is very painful, your GP may prescribe a painkiller that you can apply directly to your ulcer.

Your GP will usually prescribe benzydamine, which can either be taken in the form of a mouthwash or a spray. You will not be able to use benzydamine for more than seven days in a row.

The mouthwash form of benzydamine may sting when you first use it, but this should pass with continued use. However, if the stinging persists, contact your pharmacist or GP.

You may also find that your mouth feels numb when you first use the mouthwash. This is normal and the feeling will soon return to your mouth. When using sprays or mouthwashes, always follow the manufacturer's dosage instructions.

If you are pregnant, breastfeeding or trying to get pregnant, tell your GP or pharmacist before taking benzydamine mouthwash.
Although these treatments effectively reduce swelling and discomfort in mouth ulcers that are already present, they do not reduce the likelihood of you developing new mouth ulcers at any time during or after the treatment.

Mouth ulcers rarely cause any complications. Over time, most mouth ulcers will heal naturally. Those that do not can usually be treated with medication.

A mouth ulcer may indicate an underlying health condition, but the ulcer itself will not be the cause of any illness.

Bacterial infection

The only complication mouth ulcers can cause is a bacterial infection. However, this is very rare. In some cases, an infected ulcer can cause the bacteria to spread to other areas of your mouth, such as your teeth. If your ulcer becomes infected, you might need treatment with antibiotics.

Healthy lifestyle

To prevent getting mouth ulcers, try to avoid becoming run down by eating a healthy, balanced diet, exercising regularly and learning to manage stress effectively.

If you are prone to getting recurrent ulcers, avoid damaging the inside of your mouth by using a softer toothbrush. Also avoid hard, brittle or sharp-edged foods.

Good dental hygiene

Another way to prevent getting mouth ulcers is to make sure that your teeth are healthy by regularly visiting your dentist.

Your dentist can tell you how often you should have a check-up appointment. Depending on your oral health, the length of time before your next check-up could be as short as three months or as long as two years. The better your oral health, the less you will need to visit your dentist.

Regular dental check-ups will also reduce the risk of sharp edges of your teeth or fillings damaging the inside of your mouth.