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Mouth Ulcers

What are mouth ulcers?

Mouth ulcers are usually small, yellowish-grey and red, round to oval sores found inside your mouth. Mouth ulcers are painful and generally uncomfortable, particularly on eating and drinking. They are normally harmless, and heal within one or two weeks. More than one sore may develop, but you can neither catch them from or give them to another person. More rarely, a large sore or many very small sores may develop, which can be very painful and take several weeks to heal. Mouth ulcers are not the same as cold sores, which usually occur outside your mouth, on your lips or around your mouth, and caused by a virus.


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How common are mouth ulcers?

Mouth ulcers are common. About one-fifth of the general population are estimated to be affected by them. Mouth ulcers run in families, with children highly likely to develop the sores if their parents get them.

What causes mouth ulcers?

The most common cause of a single mouth ulcer is trauma - resulting from damage to the tissues lining the inside of your mouth. This may happen by biting your cheek or by a sharp or jagged tooth, hard brushing of teeth, ill-fitting dentures, or hard, rough pieces of food. These mouth ulcers tend to be near the cause of damage and heal once the cause is removed.

It is unknown why some mouth ulcers keep recurring, but this appears to occur in families. They may be triggered by a variety of factors such as: stress, fluctuations in hormone levels (e.g., during menstruation), toothpastes and mouth washes containing sodium lauryl sulphate, and hypersensitivity to bacteria and certain foods (e.g., chocolate, coffee, cheese, peanuts, wheat, strawberries, citrus fruits and other acidic foods, and spicy and salty foods).

Mouth ulcers may also be caused by some medical conditions, such as: viral, bacterial, and fungal infections; vitamin (folic acid, B1, B3, B6, B12) or mineral (iron, zinc) deficiencies; inflammatory diseases (e.g., coeliac disease, Crohn's disease, reactive arthritis, and a rare inflammatory disease of blood vessels [Beh├žet's disease]); and a poor immune system (though e.g., lupus, HIV). Sometimes. mouth ulcers are caused by the treatments you are using, such as: non-steroidal anti-inflammatory drugs (e.g., ibuprofen), angina and blood pressure tablets, chemotherapy, and radiotherapy.

When should a doctor be contacted?

You should contact your dentist or doctor for advice if a mouth ulcer lasts more than three weeks or worsens (becomes larger, more painful, or more ulcers develop), keeps coming back, or you are unable to eat or drink. A red, painful ulcer may indicate a bacterial infection requiring antibiotic treatment. In some cases, it may be a viral infection called hand, foot and mouth disease. In a few people, mouth ulcers are a sign of cancer of the mouth. These are usually single, long-lasting ulcers on or under the tongue, but can occur elsewhere in the mouth. Smoking, heavy alcohol drinking, and human papilloma virus infection increase the risk of mouth cancer.

How can I reduce the risk of are mouth ulcers?

You may not be able to prevent mouth ulcers where the cause is due to a family history or an underlying medical condition. However, the chances of getting mouth ulcers may be minimised by reducing your stress, avoiding trigger foods (see above), eating a healthy balanced diet and taking a vitamin/mineral supplement, using a soft toothbrush and toothpaste without sodium lauryl sulphate, and practising good oral hygiene.

Reviewed by: Dr Loraine Haslam MBBS, DRCOG, DFSRH, LoC SDI, LoC IUT, MRCGP
GMC registration number: 4524038
Date: 30 October 2023
Next review: 29 October 2025
All UK registered doctors can have their registration checked on
The Medical Register at the GMC website.
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