18 Oct 2026
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Mouth Ulcers: Causes, Relief and When to Get Checked
Most mouth ulcers heal within one to two weeks. Learn what causes them, how to ease the pain, and why an ulcer lasting more than three weeks should be checked.
Quick answer
Most mouth ulcers are small, painful sores that heal on their own within one to two weeks. Common triggers include biting the cheek, sharp teeth or braces, stress, and some foods. Salt-water rinses, avoiding spicy or acidic food and pharmacy gels can ease pain. See a dentist or doctor if an ulcer lasts more than three weeks, keeps coming back, is painless but not healing, or comes with a lump or a red or white patch.
In this article
Mouth ulcers are very common and usually harmless, though they can make eating and talking uncomfortable.
Common causes
- Accidentally biting your cheek or tongue
- Sharp or broken teeth, braces or poorly fitting dentures
- Stress and tiredness
- Hormonal changes
- Certain foods, such as spicy, acidic or very hot foods
- Some toothpastes containing sodium lauryl sulfate
- Iron, vitamin B12 or folate deficiency
- Viral infections, including cold sores inside the mouth
Relief at home
- Rinse with warm salt water several times a day.
- Use a soft toothbrush.
- Avoid spicy, salty, acidic and very hot food and drink.
- Drink cold water through a straw.
- Ask a pharmacist about gels, sprays or mouthwashes that relieve pain or protect the ulcer.
When to get checked
See a dentist or GP if:
- An ulcer lasts more than three weeks
- Ulcers keep coming back
- The ulcer is large, very painful or getting bigger
- You have ulcers with fever, weight loss or feeling unwell
- You notice a red or white patch, or a lump, in the mouth or neck
A long-lasting ulcer, especially in someone who smokes, uses shisha or chews tobacco or areca nut (paan), needs examination to rule out mouth cancer. Most turn out to be harmless, but early checks matter.
Frequently asked questions
Are mouth ulcers contagious?
Common ulcers are not. Cold sores, caused by the herpes simplex virus, are.
Can a sharp tooth cause repeated ulcers?
Yes. A dentist can smooth a sharp edge or repair a broken tooth or filling.
