Mouth Ulcers: Causes, Treatment and When to See Your Dentist

Mouth ulcers have a way of making themselves known — eating becomes a careful exercise, anything acidic is off limits, and the tongue keeps finding its way back to the sore. For something so small, they cause disproportionate discomfort.

The good news is that most mouth ulcers are harmless and heal on their own. The more useful news is knowing what causes them, what actually helps while they heal, and when one is worth getting checked.

What Are Mouth Ulcers?

Mouth ulcers are small open sores that develop on the soft tissue inside the mouth — the inner cheeks, gums, tongue, or lips. They’re typically round or oval, with a white or yellow centre and a red border, and most heal without treatment within 1 to 2 weeks.

The most common type is the aphthous ulcer — also called a canker sore. A virus does not cause these, and they are not contagious, which is a common misconception.

Unlike mouth ulcers, cold sores develop on the outer lips. Herpes simplex virus causes them and can be transmitted through direct contact, particularly when the sores are active. They’re a different condition entirely.

Aphthous ulcers range from minor — small, one at a time, resolving quickly — to major, which are larger, deeper, and take longer to heal. The minor variety is by far the more common.

What Causes Them?

Ulcers often appear without an obvious reason. These are the triggers that come up most consistently:

Minor injury

Biting the cheek, catching the gum with a toothbrush, or irritation from a sharp tooth or appliance edge are among the most common causes. The ulcer forms within a day or two and heals without intervention once the irritation is removed.

Acidic and spicy foods

Citrus fruits, tomatoes, pineapple, and spicy foods can both trigger ulcers and significantly worsen existing ones. Some toothpastes containing sodium lauryl sulphate have also been linked to increased frequency in susceptible people.

Stress

Ulcers appear more frequently during periods of physical or emotional stress, illness, or poor sleep. The connection is well documented, though the precise mechanism isn’t fully understood.

Nutritional deficiencies

Vitamin B12, iron, or folate deficiencies are linked to recurring mouth ulcers. If they keep coming back without an obvious dietary or lifestyle trigger, a blood test is worth discussing with a GP.

Hormonal changes

Some people — particularly women — notice ulcers following a predictable pattern tied to the menstrual cycle. They’re also more common during pregnancy.

What They Look Like and What to Expect

A typical minor ulcer starts as a tingling or burning sensation before the sore appears. Over the first day or two, it opens fully, then heals gradually from the edges inward. The pain is usually sharpest in the first few days and eases as healing progresses.

Most resolve within seven to fourteen days. Some people get several small ulcers at once rather than a single sore — this is common and not a sign of anything more serious. Major aphthous ulcers are larger, take several weeks to heal, and occasionally leave a small scar once resolved.

Home Care

No home treatment makes an ulcer heal significantly faster, but these measures reduce discomfort and support the healing process.

Saltwater rinse

Several times a day, gently rinse a glass of water that is warm with 1/2 teaspoon of salt dissolved in it for 30 to 60 seconds. Reduces inflammation, keeps the area clean, and discourages bacterial accumulation around the sore.

Over-the-counter gels and pastes

Topical anaesthetic gels containing benzocaine or lidocaine numb the area and take the edge off eating and drinking. Barrier pastes adhere to the ulcer surface and reduce irritation from contact with food and saliva. Both are available at pharmacies without a prescription.

Avoid triggers

Acidic, spicy, and crunchy foods aggravate ulcers and slow healing. Soft, neutral foods are easier to manage. If a particular food consistently triggers ulcers, removing it from the diet is a simple first step worth trying.

Toothpaste

If ulcers recur frequently, switching to a toothpaste without sodium lauryl sulphate may reduce their frequency. These are available at most pharmacies.

What to avoid

Don’t attempt to scrub or burst the ulcer — it slows healing and heightens the risk of infection. Alcohol-based mouthwashes irritate the tissue and should be avoided until the ulcer has resolved.

When to See a Dentist

Most ulcers clear up without any professional intervention. Book an appointment if:

• An ulcer hasn’t healed after three weeks
• It’s larger than a centimetre across
• Ulcers are recurring frequently with little gap between episodes
• Multiple ulcers are appearing at the same time regularly
• The ulcer is accompanied by fever, swollen lymph nodes, or difficulty swallowing
• A sore is painless — painless ulcers are less typical and worth having assessed
• A sore bleeds without being touched, has an irregular border, or appears on the floor of the mouth or under the tongue

Any ulcer that doesn’t follow the typical pattern — particularly one that persists beyond three weeks — should be assessed to rule out other causes, including oral cancer.

Frequently Asked Questions

Are mouth ulcers contagious?

No. A virus does not cause aphthous ulcers and can’t be passed on through kissing, sharing food, or any other contact. Cold sores are contagious, but they appear on the outer lip rather than inside the mouth. If you’re not sure which you or your child has, your North Lakes dentist can tell the difference at a glance.

Why do I keep getting mouth ulcers?

Recurring ulcers are common and usually linked to stress, diet, hormonal changes, or low B12, iron, or folate. Identifying and avoiding personal triggers reduces frequency for most people. If ulcers are persistent and disruptive without a clear cause, a dental or GP review is worthwhile.

How long should a mouth ulcer last?

Minor aphthous ulcers typically heal within seven to fourteen days. Major ulcers can take several weeks. An ulcer still present at three weeks should be professionally assessed.

Can children get mouth ulcers?

Yes — they’re common in children and teenagers. Causes and home management are the same as for adults. Frequent, large, or unusually painful ulcers in children are worth bringing up at a dental check-up rather than managing them indefinitely at home.

Is there anything that prevents mouth ulcers?

No guaranteed prevention, but identifying personal triggers — specific foods, toothpaste ingredients, stress — and avoiding them reduces frequency. Maintaining adequate B12, iron, and folate levels helps in patients with deficiency.

Oral Health in North Lakes

If you have a mouth ulcer that hasn’t healed after three weeks, keeps coming back, or doesn’t look like a typical ulcer, get it assessed.

At Passion Family Dental North Lakes, we welcome patients from Mango Hill, Griffin, Murrumba Downs, and Kallangur.

Call us on (07) 3465 1199 or book online.

Visit us at Unit 4/6 Endeavour Boulevard, North Lakes.