Down in the mouth? We've got the measure of mouth ulcers!

Mouth Ulcers: Common Causes, Latest UK Guidance, Treatment and When to Get Help

What Are Mouth Ulcers?

Mouth ulcers are very common, uncomfortable sores that appear inside the mouth — typically on the inside of the cheeks, lips, gums or tongue. Most people in the UK will experience one or two mouth ulcers a year, and up to 20% of adults report recurrent episodes. They are more common in young adults and women, and it is unusual for someone to first develop mouth ulcers after the age of 30.

Typical symptoms include:

  • Painful sores with red, swollen edges

  • A centre that may be white, yellow, grey or red

  • Discomfort when eating, drinking or brushing teeth

Most ulcers are small (about 0.5 cm across) and harmless, healing on their own within a week or two.

Important: Painless ulcers — particularly those lasting longer than three weeks — are less common and may require professional assessment.

Why Mouth Ulcers Happen

Most mouth ulcers are “one-off” and result from minor injuries to the mouth lining, such as:

  • Biting the cheek or tongue

  • Sharp edges on teeth or fillings

  • Poorly fitting dentures

  • Burns from hot food or drinks

Other potential triggers include:

  • Stress or anxiety

  • Certain foods (e.g. chocolate, nuts, tomatoes, wheat products)

  • Toothpaste containing sodium lauryl sulphate

  • Hormonal changes (for example, around menstrual periods)

  • Abrupt smoking cessation (ulcers may flare before settling)

Self-Care and First-Line Treatments

Most mouth ulcers will heal without treatment.

Try the following home care strategies:

  • Avoid spicy, acidic or rough foods

  • Use a soft-bristled toothbrush

  • Drink cool drinks — a straw can help avoid direct contact with ulcers

  • Rinse with saline solution (½ teaspoon salt in warm water)

  • Reduce stress where possible

  • Have regular dental check-ups

If your symptoms are uncomfortable, a pharmacist can recommend treatments such as:

  • Antimicrobial or analgesic mouthwash

  • Topical pain relief gels or sprays

  • Mild steroid mouthpaste or tablets — where necessary and safe
    Always check with the pharmacist before using OTC treatments, especially in children, pregnancy or breastfeeding.

Medical and Prescription Treatment

If self-care and pharmacy options aren’t enough, a dentist or GP may prescribe:

  • Stronger corticosteroid pastes or dissolving tablets

  • Analgesic gels or prescription mouthwash

  • Antibacterial solutions if there’s suspected infection
    These are typically used when ulcers are large, particularly painful or recurrent.

When to See a GP or Dentist

You should contact your GP or dentist if:

  • A mouth ulcer lasts longer than 3 weeks — persistent ulcers may require further assessment and could be referred under UK suspected cancer pathways.

  • The ulcer is more painful, larger or bleeding

  • You have multiple or recurrent mouth ulcers

  • You notice other symptoms such as unexplained weight loss, rashes, joint pain or ulcers elsewhere on the body

NICE urgent cancer referral guidance indicates that an unexplained oral ulcer lasting more than three weeks should be considered for suspected cancer referral, usually via an urgent “2-week wait” pathway.

Mouth Cancer: while rare compared with benign ulcers, around 7,500 new cases of mouth cancer are diagnosed in the UK each year, and early detection significantly improves outcomes. Persistent ulcers, especially in people who smoke or drink heavily, should be checked promptly.

Underlying Conditions That May Contribute

Recurrent or severe mouth ulcers can sometimes indicate an underlying health issue, including:

  • Nutrient deficiencies (iron, vitamin B12, folate)

  • Inflammatory bowel conditions (e.g. Crohn’s disease)

  • Coeliac disease

  • Autoimmune conditions (e.g. lichen planus, lupus)

  • Certain medications (e.g. NSAIDs such as aspirin and ibuprofen, beta-blockers, nicorandil)

  • Viral infections (e.g. hand, foot and mouth disease or cold sore viruses)

Your GP may order blood tests or other investigations if an underlying cause is suspected.

What to Expect at Your Appointment

Your GP or dentist will typically ask about:

  • Duration and frequency of ulcers

  • Smoking and alcohol use

  • Family history

  • Other symptoms (weight changes, rashes, joint pain)

They will examine your mouth and may feel your neck for swollen lymph glands. Blood tests may be requested, and if an ulcer looks unusual or persistent, referral to a specialist (such as an oral surgeon) and potential biopsy may be advised.

Key Takeaways

  • Most mouth ulcers are harmless and self-resolving within 1–2 weeks.

  • Use self-care and pharmacy options for pain relief and to speed healing.

  • See a GP or dentist if an ulcer lasts more than 3 weeks, is recurrent or severe — NICE guidance supports timely referral for suspected cancer if there’s no clear cause.

  • Persistent ulcers may sometimes signal nutrient deficiencies, systemic disease or, very rarely, mouth cancer.

If you’re concerned about your mouth ulcer — especially if symptoms are unusual, persistent, or worsening — please make an appointment with your GP or dentist.