What causes mouth ulcers and how to prevent them

Although harmless, mouth ulcers can be extremely painful. We look at the causes, treatment and prevention tips.

Mouth ulcers are small painful sores that form in the mouth.
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Mouth ulcers are an extremely common oral condition that can be painful and uncomfortable. During the winter months when people are run down they do become more susceptible to mouth ulcers, but the good news is they're mostly harmless and usually clear up on their own within a week or two.

So what causes mouth ulcers and what's the best way to get rid of them? We look at the symptoms, causes and treatment options for mouth ulcers:

What are mouth ulcers?

Mouth ulcers are small painful sores that form in the mouth. The most common type are called aphthous or simple ulcers. These are recurrent and often date from childhood, and sometimes run in families.

There are three main types of aphthous ulcers:

• Minor ulcers

Minor ulcers are small, non-scarring and usually heal without any treatment within two weeks. The most common type, they cause around three quarters of all mouth ulcers.

• Major ulcers

Major ulcers are 1cm or larger, have a raised border and can last from two weeks to several months. Usually only one or two appear at a time. They can be very painful and cause difficulty eating, are slower to heal and can leave scars. About 10 per cent of ulcers are this type.

• Herpetiform ulcers

Herpetiform ulcers are multiple tiny sores that can be very painful – particularly if they fuse together to form one larger sore. They can last from one week to two months. Despite their name, they seem to have nothing to do with the herpes virus. They are uncommon.

Aphthous ulcers aren't contagious, so you can't pass them on by kissing or sharing utensils. There are other conditions that cause problems in the mouth – such as yeast, bacterial or viral infections, which may be contagious.



Who's at risk of mouth ulcers?

Most people have at least one attack of mouth ulcers in their lifetime, but mouth ulcers are more common in women and those under the age of 40.

Up to one in five people have repeated attacks of aphthous ulcers.

More than a third of people with recurrent aphthous ulcers have a family history of them. This figure rises to over 80 per cent if both parents get frequent mouth ulcers.

What causes aphthous mouth ulcers?

A number of factors can causes aphthous mouth ulcers including damage to the mouth, medical conditions and certain medications:

Minor mouth ulcer triggers

Minor mouth ulcers are usually triggered by damage to the mouth from the following:

  • Accidentally (or deliberately) biting the inside of the cheek.
  • Over-vigorous tooth brushing.
  • A sharp tooth, filling or appliance (eg orthodontic or denture).

    Recurrent mouth ulcer risk factors

    Although there may be no obvious reason why the ulcers keep returning, factors that can increase the risk include:

    • Mouth trauma, such as excessive brushing or chewing hard food.
    • Anxiety and stress can increase your risk of mouth ulcers.
    • Certain foods such as chocolate, coffee, nuts, strawberries and cheese.
    • Some women also find they get mouth ulcers during their period.
    • Stopping smoking can initially trigger mouth ulcers in the first few weeks after quitting, but this tends to settle down after that.

      Medical conditions that can cause mouth ulcers

      Certain medical conditions can also make these and other types of mouth ulcers more likely, such as:

      • Vitamin B12 deficiency
      • Viral infections – a common trigger
      • Iron deficiency
      • Coeliac disease (intolerance to a protein called gluten, found in wheat, rye and barley)
      • Crohn's disease
      • Behçet's disease
      • Autoimmune disorders
      • Reiter's syndrome (urethral discharge followed by conjunctivitis and arthritis)
      • HIV infection.

        Medication that can cause mouth ulcers

        Occasionally, mouth ulcers can be caused by medication. Common examples include:

        • Painkillers, such as ibuprofen and aspirin
        • Nicorandil and beta-blockers that are used in heart conditions
        • Agents used in cancer chemotherapy often cause ulcers.


          Mouth ulcer symptoms

          Most mouth ulcers are easy to spot because they are round or oval in shape, whitish in colour and usually inflamed around the edge.

              Mouth ulcers are usually seen on the inside of the lips and cheeks, on the floor of the mouth and under the tongue. They usually cause pain, especially when eating and drinking.

              Mouth ulcers and medical conditions

              Some medical conditions can cause mouth sores and ulcers with different symptoms.

              • Oral thrush

              Thrush usually takes the form of whitish or yellow spots in the mouth that are often raised but not usually painful. They can sometimes cause a burning sensation and a bad taste in the mouth.

              • Lichen planus

              Lichen planus can cause white dots or irregular white streaks with a net-like appearance on the inside of the cheeks or the roof of the mouth. Ulcers can develop and cause soreness that is often made worse by hot or spicy food.

              • Gum disease and bacterial infections

              Gum disease and bacterial infections typically cause painful, bleeding gums that are red and swollen. You'll need to see your dentist to get this treated.



              When to see the doctor about mouth ulcers

              Simple mouth ulcers do not usually require any formal diagnosis from a doctor. You should seek medical advice if any of the following applies:

              • You have a single mouth ulcer lasting more than three weeks.
              • Your mouth ulcer gets progressively more painful and inflamed.
              • Ulcers appear elsewhere on the body.
              • You feel unwell or have other symptoms you are worried about.

                Tests your doctor may carry out

                If the cause or type of mouth ulcer is unclear, your doctor may do some tests to help reach a diagnosis. These may include:

                • A full blood count to look at your general health.
                • A test for inflammation in the body called an ESR (erythrocyte sedimentation rate).
                • Checking the iron level in the body (ferritin).
                • Checking levels of vitamin B12.
                • Blood tests to check for autoimmune conditions.

                  If your mouth ulcers persist for more than three weeks, especially if they are very painful or severe, your doctor may refer you to a specialist at your local hospital.



                  Mouth ulcers and oral cancer

                  You will be referred to a specialist if you have persistent abnormal-looking areas of ulceration. This is because in a very small number of cases, an ulcer may be a sign of oral cancer.

                  The risk of this increases if you are male, over 45 and a heavy smoker or drinker. The recovery rate for mouth cancer is good if spotted early enough, so you should get any persistent mouth ulceration checked out and have regular check-ups with your dentist.

                  Mouth ulcer treatment

                  Fortunately, most mouth ulcers do not need specific treatment and heal naturally without medication.

                  You can help a mouth ulcer to heal faster by avoiding hard or irritant foods.

                  A dentist, doctor or pharmacist can advise you on the most suitable medication for an ulcer. If an ulcer is very painful, the painkiller benzydamine may be prescribed as a mouthwash or a spray.



                  Can you prevent mouth ulcers?

                  There is no sure-fire way to prevent most mouth ulcers, but the following may help if you get them a lot.

                  ✔️ Keep stress levels as low as possible.

                  ✔️ Eat a healthy diet.

                  ✔️ Avoid any foods, medications or oral healthcare products that trigger mouth ulcers.

                  ✔️ Make sure you have regular dental check-ups.



                  Last updated: 16-10-19

                  Dr Juliet McGrattan Dr Juliet McGrattan spent 16 years working as an NHS GP.
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