Mouth Ulcers: When They’re Normal and When to Worry

That sharp, stinging sore inside your cheek that makes eating feel like a chore — you’ve probably had one before. Mouth ulcers are a common oral concern and, while usually harmless, they can be quite uncomfortable.

The real question isn’t whether you’ve had one — it’s knowing when to leave it alone and when it’s time to get it looked at.

What Are Mouth Ulcers?

Aphthous ulcers, commonly referred to as mouth ulcers, are small, shallow sores that appear on the soft tissues inside the mouth. They’re typically round or oval with a white or yellow centre and a red border. They can appear on the inner cheeks, tongue, gums, or the inside of the lips.

They’re not the same as cold sores, and they’re not contagious. But they are painful — especially when you eat, drink, or speak.

There are three types:

• Minor ulcers are the most common. They’re small (under 10mm), heal on their own within one to two weeks, and don’t leave scarring.
• Major ulcers are larger and deeper. They take longer to heal — sometimes several weeks — and can leave a scar.
• Herpetiform ulcers appear as clusters of many tiny sores. Despite the name, they have nothing to do with the herpes virus. They’re rare and tend to affect adults more than children.

 

Common Causes

Most mouth ulcers don’t have a single obvious cause. A combination of triggers is usually responsible.

Physical injury is one of the most frequent. Accidentally biting the inside of your cheek, catching it on a sharp piece of food, or irritation from dental appliances like braces or ill-fitting dentures can all break the tissue and trigger an ulcer.

Stress and hormonal changes are closely linked to outbreaks. Many people notice ulcers appearing during periods of high stress, around their menstrual cycle, or during other hormonal shifts.

Nutritional deficiencies—particularly low levels of vitamin B12, iron, and folate—are common underlying factors, especially among those with recurring mouth ulcers. If your diet is limited or your absorption is poor, this is worth investigating.

Food sensitivities to acidic foods (such as tomatoes and citrus), spicy foods, or certain additives can trigger flare-ups in some people. This doesn’t mean you need to eliminate these foods permanently — just be aware of patterns.

Medicines, including non-steroidal anti-inflammatory drugs (NSAIDs), beta-blockers, and some chemotherapy drugs, can cause or worsen mouth ulcers as a side effect.

Underlying health conditions such as coeliac disease, Crohn’s disease, or immune system disorders may also contribute to persistent or recurring ulcers. If you’re experiencing frequent outbreaks with no clear trigger, this is worth discussing with your doctor or dentist.

Home Remedies and Self-Care

For most minor ulcers, you won’t need a prescription or a dental visit. Here’s what actually helps:

• Salt water rinse—Prepare a rinse of 1/2 teaspoon of salt dissolved in warm water, then swish for 30 to 60 seconds. It’s not pleasant, but it helps reduce inflammation and keeps the area clean.
• Over-the-counter gels and pastes— Topical treatments containing benzocaine or carmellose sodium create a protective barrier over the ulcer and reduce pain. These are available at most pharmacies.
• Avoiding irritants—such as spicy, acidic, and crunchy foods—can aggravate healing tissue. Stick to a soft diet while the ulcer is active. Think yoghurt, mashed vegetables, soups, and smoothies.
• Ice chips— Applying ice chips to the ulcer may provide temporary relief by numbing the area.
• Pain relief — When an ulcer interferes with eating or sleeping, standard pain relievers like paracetamol or ibuprofen may help ease symptoms.
• Antiseptic mouthwash — A chlorhexidine-based mouthwash can help prevent secondary infection, particularly if the ulcer is in a hard-to-clean area.

Avoid touching or prodding the ulcer with your tongue or fingers. This may slow healing and raise the likelihood of irritation.

When to See Your Dentist

Most mouth ulcers resolve on their own within 1 to 2 weeks without treatment. But there are specific signs that warrant a professional assessment — and they’re worth knowing.

The ulcer hasn’t healed after three weeks. This is the key threshold. An ulcer that persists beyond three weeks should always be examined. While there’s usually a benign explanation, a long-lasting ulcer is one of the early signs that prompts oral cancer screening. Catching any changes early makes a significant difference.

The ulcer is unusually large — larger than a centimetre — or it’s causing significant pain that isn’t easing.

You’re experiencing recurring mouth ulcers — multiple outbreaks per year with short gaps between them. Recurring ulcers can signal an underlying nutritional deficiency, immune issue, or digestive condition that needs attention.

The ulcer is affecting your ability to eat, drink, or swallow. If it’s interfering with basic function, don’t wait it out.

You have accompanying symptoms such as fever, swollen lymph nodes, or skin rashes. These suggest a systemic cause that needs medical assessment.

New ulcers keep appearing before old ones heal. This pattern is not normal and should be investigated.

At Canley Heights Dental Care, we regularly see patients with persistent or recurring ulcers. An examination helps rule out anything more serious and, where needed, we can arrange referrals or recommend targeted treatment.

Mouth Ulcers vs Cold Sores — They’re Not the Same

This is one of the most common points of confusion, and it’s worth clearing up.

• Location — Mouth ulcers form inside the mouth on soft tissue: cheeks, tongue, gums, inner lips. Cold sores appear outside the mouth, typically on or around the outer lip.
• Cause— Mouth ulcers have multiple possible triggers (stress, injury, deficiencies). The herpes simplex virus (HSV-1) is the underlying cause of cold sores.
• Contagious? — Mouth ulcers are not contagious. Cold sores are highly contagious through direct contact, especially when active or blistering.
• Appearance — Cold sores begin as a tingling sensation, then develop into a cluster of fluid-filled blisters that burst and crust over. Mouth ulcers are open sores, not blisters.
• Treatment— Cold sores respond to antiviral medicines. Mouth ulcers are managed with topical gels, rinses, and supportive care. The treatments are not interchangeable.

If you’re not sure which you’re dealing with — particularly if sores keep appearing in the same spot — it’s worth having it assessed rather than guessing.

Frequently Asked Questions

Are mouth ulcers contagious?

No. Infectious viruses or bacteria do not cause mouth ulcers (aphthous ulcers), so they cannot be spread to others. They cannot spread through kissing, sharing utensils, or any form of contact. Cold sores are contagious — but they are a separate condition.

Can stress cause mouth ulcers?

Yes, stress is one of the most well-documented triggers. Emotional or physical stress can affect immune function, creating conditions that increase the likelihood of ulcer development. Many people notice outbreaks during demanding periods at work, illness, or sleep deprivation.

How long does a mouth ulcer take to heal?

Minor ulcers typically heal within seven to fourteen days. Major ulcers can take several weeks. If yours hasn’t resolved after three weeks, see your dentist.

Should I be worried about oral cancer?

Most mouth ulcers are completely benign. However, an ulcer that hasn’t healed after three weeks, is painless, firm to the touch, or keeps returning in the same spot should be examined. Your Canley Heights dentist can assess whether further investigation or an oral cancer screening is needed. Concern is reasonable — panic isn’t. The key is not to ignore it.

Why do I keep getting mouth ulcers?

Recurring mouth ulcers often point to an underlying trigger: low B12, iron, or folate levels; food sensitivities; hormonal fluctuations; or an immune-related condition. Keeping a simple log of when ulcers appear — what you ate, your stress level, where you are in your cycle — can help identify patterns. If they’re frequent, bring this to your dentist or GP.

Can children get mouth ulcers?

Yes. Children can develop aphthous ulcers just as adults do. If your child has an ulcer that seems unusually large, won’t heal, or is accompanied by a fever, have it assessed.

Mouth Ulcers Management in Canley Heights

If you have a mouth ulcer that’s been hanging around, keeps coming back, or doesn’t feel right, don’t sit on it.

At Canley Heights Dental Care, we provide thorough oral examinations for patients across Canley Heights, Canley Vale, Cabramatta, Fairfield, and Wakeley who are dealing with persistent or recurring ulcers. We’ll assess what’s going on, help identify potential triggers, and refer on where necessary.

Call us on (02) 9199 9678 or book online. Visit us at 1/229 Canley Vale Road, Canley Heights.