Almost everyone gets a mouth ulcer at some point. Most clear up on their own within a week or two, without any lasting concern. But mouth ulcer causes vary quite a bit, and some patterns are worth paying closer attention to. This guide covers what typically causes them, how to ease the discomfort, and the situations where it’s genuinely worth booking a check-up. It’s written to help you tell the difference between a normal, self-limiting ulcer and one that deserves a proper look.
What a mouth ulcer actually is
A mouth ulcer is a small, painful sore on the soft tissue inside the mouth. It can appear on the inner cheek, lips, tongue, or gums. It usually looks like a round or oval spot, with a white or yellow centre and a red border.
Most are what’s known as aphthous ulcers, sometimes called canker sores. They’re not contagious, and having one doesn’t mean you can pass it on to anyone else. They’re also different from cold sores, which are caused by the herpes virus and usually appear on the outside of the lips.
The most common mouth ulcer causes
Minor trauma. Accidentally biting your cheek is a common trigger. So is a sharp edge on a filling or brace, or brushing too hard. This is one of the most frequent mouth ulcer causes we see in practice.
Stress and tiredness. Ulcers often flare up during particularly busy or stressful periods. The exact reason for this link isn’t fully understood, but the pattern is a common one.
Certain foods. Acidic or spicy foods trigger ulcers in some people. So do things like chocolate, coffee, and nuts. This varies a lot from person to person.
Hormonal changes. Some people notice ulcers appearing at particular points in their menstrual cycle. This suggests a hormonal link for at least some cases.
Vitamin or mineral deficiencies. Low levels of iron, vitamin B12, or folate are linked to more frequent ulcers in some people.
Certain toothpaste ingredients. Sodium lauryl sulphate, a foaming agent in many toothpastes, has been linked to ulcers in sensitive individuals. Switching to an SLS-free toothpaste sometimes helps.
Underlying health conditions. Conditions like Crohn’s disease, coeliac disease, and some autoimmune conditions can cause more frequent or unusually persistent ulcers.
Mouth ulcers in different locations
Where an ulcer appears can offer a small clue about its likely cause.
Mouth ulcer on the tongue. These are often linked to accidental biting, or a sharp edge on a tooth. They can be particularly uncomfortable, given how much the tongue moves during eating and speaking.
Mouth ulcer on the gum. These are sometimes linked to irritation from a denture, a brace, or aggressive brushing near the gumline. That’s different from the more general triggers affecting the cheek or lip.
In most cases, the location doesn’t change the treatment. But it’s still useful information for us. If ulcers keep coming back in the same spot, that often points to a specific, fixable trigger.
How to get rid of a mouth ulcer faster
Most ulcers heal within one to two weeks regardless of treatment. A few things still help with comfort and healing time in the meantime.
- Rinse with warm salt water a few times a day
- Use an over-the-counter mouth ulcer gel to numb the area before eating
- Avoid acidic, spicy, or very hot food and drink while it heals
- Use a soft-bristled toothbrush around the affected area rather than skipping brushing entirely
- Consider an antiseptic mouthwash if the area feels irritated
None of these speed up healing dramatically. But they make the week or two of discomfort considerably more manageable.
Recurring mouth ulcers
If you get mouth ulcers regularly, it’s worth thinking about whether there’s a pattern. Recurring mouth ulcers linked to a specific food, a rough edge on a tooth or filling, or a period of high stress often point to something fixable once it’s identified.
If they’re recurring without any obvious trigger, or happening more often than every few months, mention it to us at a check-up. Sometimes a simple change, like adjusting a sharp filling edge or switching toothpaste, makes a real difference.
When a mouth ulcer needs proper attention
Most ulcers are harmless and self-limiting. But a few signs suggest it’s worth getting checked rather than waiting it out.
- A mouth ulcer that won’t heal after three weeks
- An ulcer that keeps getting bigger rather than smaller
- Unusual bleeding from the ulcer
- An ulcer that isn’t painful, which is unusual and worth a proper look
- Ulcers appearing alongside other symptoms like fever or swollen glands
- Very frequent ulcers, especially if several appear at once regularly
These signs don’t automatically mean anything serious. Most of the time, there’s still a straightforward explanation. But a persistent, non-healing ulcer is worth ruling out properly. It’s better than assuming it will eventually clear up on its own.
What we look for at a check-up
If you come to us with a concerning ulcer, we’ll take a proper look at it. We’ll also check your general oral health and ask about anything that might be contributing: diet, stress, recent dental work, or any other symptoms. Regular dental check-ups are also a natural point for us to spot recurring irritation from a filling, denture, or brace, before it becomes a repeated problem.
If irritation from plaque or tartar build-up near the gumline seems to be playing a role, a proper clean from a dental hygienist can also help. This reduces how often ulcers appear in that area.
Why we take persistent ulcers seriously
We’re not trying to cause alarm here. The overwhelming majority of mouth ulcers are completely benign. But a mouth ulcer that hasn’t healed after three weeks is one of the recognised warning signs dentists are trained to check carefully. Catching anything unusual early simply makes a genuine difference. At Smile Perfections, this is a routine part of what we look for at every check-up, not something we treat as an afterthought.
If you’ve had an ulcer for longer than usual, or one just doesn’t feel right, it’s always worth getting it looked at. Waiting to see if it resolves isn’t the safer option.
A quick note on prevention
While not every ulcer can be avoided, a few habits reduce how often they show up for many people. Keeping any sharp fillings, crowns, or brace components smoothed down helps, as does using a soft-bristled toothbrush and a gentle technique. If certain foods seem to trigger yours, keeping a rough note of what you ate before an ulcer appeared can help spot a pattern over a few months.
Frequently asked questions
What are the most common mouth ulcer causes? Minor trauma, such as accidentally biting your cheek or a sharp edge on a tooth or filling, is one of the most common causes. Stress, certain foods, hormonal changes, and some toothpaste ingredients are also frequent triggers.
How long should a mouth ulcer take to heal? Most ulcers heal within one to two weeks without any specific treatment. If an ulcer hasn’t healed after three weeks, it’s worth having it checked rather than continuing to wait.
What’s the fastest way to get rid of a mouth ulcer? Salt water rinses, over-the-counter ulcer gels, and avoiding acidic or spicy food while it heals all help with comfort. Most ulcers still take one to two weeks to fully resolve regardless of treatment.
Why do I keep getting mouth ulcers? Recurring mouth ulcers are often linked to a specific trigger, such as a sharp tooth edge, certain foods, stress, or a vitamin deficiency. If they keep happening without an obvious cause, it’s worth discussing at a check-up.
When should I see a dentist about a mouth ulcer? See a dentist if an ulcer hasn’t healed after three weeks, keeps growing, bleeds unusually, or appears alongside other symptoms like fever. Very frequent ulcers are also worth mentioning, even if each one heals normally on its own.
If you’ve got a mouth ulcer that’s lasting longer than expected, or you’re getting them more often than feels normal, get in touch. We’ll take a proper look.
Medically reviewed by Dr Juttes Pallipatt, Clinical Director at Smile Perfections, GDC number 104499.
