Mouth ulcers are one of the most common reasons people search for help with a sore mouth. Most are harmless and heal on their own within one to two weeks, but they can make eating, talking and brushing uncomfortable. This guide explains what causes mouth ulcers, what you can do at home, and when an ulcer should be checked. Mouth ulcers are also called canker sores or aphthous ulcers, and some families know them as an olsa in the mouth.
What does a mouth ulcer look like?
A typical mouth ulcer is a small round or oval sore with a white, grey or yellow centre and a red border. Ulcers can appear on the inside of the cheeks and lips, on the tongue, on the gums or on the floor of the mouth. They are often tender, especially when eating salty, spicy or acidic food.
What causes mouth ulcers?
- Minor injury – biting your cheek, a sharp or broken tooth, a rough filling, braces or a denture that rubs.
- Recurring (aphthous) ulcers – also called canker sores. The exact cause is not fully understood, but stress, tiredness and hormonal changes can be triggers.
- Toothpaste ingredients – some people find toothpastes containing sodium lauryl sulfate (SLS) trigger ulcers.
- Low iron, vitamin B12 or folate – deficiencies can be linked to frequent ulcers.
- Medical conditions – such as coeliac disease and inflammatory bowel disease.
- Viral infections – including cold sores and hand, foot and mouth disease.
- Some medicines – a small number of medications can cause mouth ulcers as a side effect.
How to get rid of mouth ulcers at home
There is no proven way to make an ulcer disappear overnight, but you can reduce pain and help it heal:
- Rinse with warm salty water (half a teaspoon of salt in a glass of warm water) a few times a day.
- Avoid spicy, salty, acidic and very hot foods until the ulcer settles.
- Use a soft toothbrush and brush gently around the area.
- Ask your pharmacist about protective gels, pastes or numbing products for mouth ulcers.
- Try an SLS-free toothpaste if you get ulcers often.
- Drink through a straw if cold or acidic drinks sting.
If an ulcer keeps forming in the same spot, there may be something rubbing it, such as a sharp tooth edge, a chipped filling or a denture. A dentist can find and fix the cause.
When should you see a dentist or doctor about a mouth ulcer?
Make an appointment with your dentist or GP if you notice:
- An ulcer that has not healed after three weeks
- An ulcer or lump that is not painful
- Ulcers that keep coming back, or several at once
- A very large ulcer, or pain that stops you eating or drinking
- Fever, feeling unwell, or difficulty swallowing
- A white or red patch that does not rub off
Most long-lasting ulcers turn out to be harmless, but a non-healing ulcer should always be checked because it can occasionally be an early sign of mouth cancer. Read more in our guide to mouth cancer signs and symptoms.
Mouth ulcer FAQs
Are mouth ulcers contagious?
Common mouth ulcers (canker sores) are not contagious. Cold sores, which usually appear on or around the lips, are caused by a virus and can spread through close contact.
Why do I get ulcers on my gums or tongue?
Ulcers on the gums or tongue are usually caused by the same things as ulcers elsewhere, often minor injury from brushing, food or a sharp tooth. A sore on the gum next to a tooth that looks like a pimple may instead be a sign of infection – see our article on sores inside the mouth.
Can mouth ulcers get infected?
It is uncommon. Increasing pain, swelling, pus or fever are reasons to see a dentist or GP.
Have an ulcer that will not heal?
If something in your mouth is not healing or you are unsure what it is, the team at Penrith Dental Care can take a look. Call (02) 4733 1197 or book an appointment online.
For more general health information, see healthdirect: mouth sores and ulcers.
Related reading
- Sore Inside Cheek: Common Causes of Mouth Sores and Bumps
- Mouth cancer: signs, symptoms and when to get checked
- Dry Mouth: Causes, Remedies and How It Affects Your Teeth
- Dental Check-Ups in Penrith
Looking for more dental health tips? Browse all articles on the Penrith Dental Care blog, or meet the Penrith Dental Care team. Have a question? See our dental FAQ.
This article is general information and does not replace advice from your own dental practitioner.