Mouth Ulcers: Causes, Treatment and When to See a Dentist
- Star Light Dental
- March 26, 2026
- [email protected]
Almost everyone gets a mouth ulcer at some point. They are small, they are harmless in the vast majority of cases, and they hurt out of all proportion to their size, especially when orange juice or a salt-and-vinegar chip finds them.
Most heal without any help within a week or two. The important thing is knowing what speeds that up, what slows it down, and the one rule that tells you when an ulcer needs to be looked at.
1. What Is a Mouth Ulcer?
The common type is called an aphthous ulcer. It is a shallow, round or oval sore with a white or yellowish centre and a red border, found on the soft lining of the mouth: inside the lips and cheeks, under the tongue, or on the soft palate. Most are only a few millimetres across and heal in 7 to 14 days without scarring.
They are not contagious and they are not caused by poor hygiene.
2. Ulcer or Cold Sore?
People often confuse the two. A mouth ulcer forms inside the mouth on soft, movable tissue and cannot be passed on. A cold sore is caused by the herpes simplex virus, usually appears on or around the lips as a cluster of small blisters that crust over, and is contagious. If you have an active cold sore, let us know before your appointment, as it may be better to reschedule.
3. What Causes Mouth Ulcers?
- Minor injury: biting your cheek, a slip of the toothbrush, a sharp tooth or filling, braces, or a denture that rubs.
- Stress and tiredness.
- Hormonal changes around a period.
- Certain foods, particularly acidic or spicy ones, in people who are prone.
- Low iron, vitamin B12 or folate.
- Medical conditions such as coeliac disease and inflammatory bowel disease.
- Some medications, and sometimes the weeks after quitting smoking.
Some people also find that a toothpaste without the foaming agent sodium lauryl sulphate reduces how often they get them.
4. What Actually Helps
- Rinse with warm salty water a few times a day.
- Avoid spicy, salty, acidic and very hot foods until it heals.
- Use a soft toothbrush and keep brushing. A clean mouth heals faster.
- Ask your pharmacist about a protective paste or gel, or an antiseptic mouthwash.
- If a sharp tooth, broken filling or denture is the cause, have it smoothed or adjusted, or the ulcer will keep coming back in the same place.
5. The Two-Week Rule
Any ulcer that has not healed after two weeks should be examined by a dentist or doctor. The overwhelming majority turn out to be nothing serious, but a sore that does not heal is the most common early sign of oral cancer, and oral cancer found early is far more treatable. Be particularly careful if the ulcer is painless, has a hard or raised edge, or if you smoke or drink alcohol regularly.
Dentists check the lining of the mouth, the tongue and the throat at every routine check-up, which is one more reason not to skip them.
6. Other Reasons to Get It Checked
- ulcers that are unusually large, or that come in crops
- ulcers that return every few weeks
- ulcers along with a fever, a rash, or sores elsewhere on the body
- ulcers that make it hard to eat or drink, especially in children, who can become dehydrated quickly
- in young children, mouth sores together with spots on the hands and feet, which suggest hand, foot and mouth disease and are a matter for your GP
Frequent ulcers are worth a blood test through your GP to check iron, B12 and folate.
Had an Ulcer for More Than Two Weeks?
Do not wait and wonder. Call Star Light Dental in Prestons on (02) 9432 2833 or book online. A look takes a few minutes and usually ends in reassurance.
This article is general information and does not replace an examination by a dentist or doctor.