Mouth ulcers

Also called Aphthous ulcers, Canker sores

Almost always harmless. The one that does not heal in three weeks is the reason this entry exists.

What it is

Mouth ulcers are extremely common. Most are aphthous ulcers: small, painful, round or oval, and they heal in one to two weeks without treatment.

They are not infectious and they are not usually caused by anything serious. Triggers include minor injury, stress, hormonal changes, certain foods, and stopping smoking.

The reason they earn an entry is the exception. A mouth ulcer that has not healed after three weeks needs urgent assessment for mouth cancer. Around 8,800 people are diagnosed with mouth cancer in the UK each year, and survival depends heavily on how early it is found.

Recurrent ulcers can also point at something treatable: iron, B12 or folate deficiency, coeliac disease, inflammatory bowel disease, or Behçet's disease.

Signs you might notice

Painful round or oval sores inside the mouth, white or yellow with a red border.

Healing within one to two weeks.

Red flags: an ulcer lasting more than three weeks, a lump in the mouth or neck, a red or white patch that will not go, persistent hoarseness, difficulty swallowing, or unexplained loosening of teeth.

Recurrent crops of ulcers, or ulcers with other symptoms such as diarrhoea, fatigue or genital ulcers, need investigating.

How it can affect day-to-day life

Eating and drinking hurt, so intake drops. In older people and people with a learning disability that can tip into dehydration and malnutrition quickly.

In somebody who cannot report pain, refusing food, pulling at the mouth or new distress at mealtimes should prompt somebody to look inside.

Dentures that rub cause ulcers, and an ulcer under a denture that persists is exactly the one that needs checking.

Supporting someone well

Look in the mouth. If you provide personal care, this is part of it.

Use the three-week rule and act on it. That single rule is what catches mouth cancer early.

Ease the pain with a topical gel, a salt water rinse, or an antimicrobial mouthwash, and avoid acidic, spicy and rough foods.

Use a soft toothbrush and check for a sharp tooth or ill-fitting denture causing the trauma.

Check iron, B12 and folate in anybody with recurrent ulcers.

Do not smoke, and keep alcohol moderate; both are the main risk factors for mouth cancer.

Where to get help

A pharmacist can advise on relief.

See a dentist or GP urgently for any ulcer lasting over three weeks. Dentists are often the fastest route.

The Oral Health Foundation run a mouth cancer awareness helpline.