Mouth ulcers are extremely common and almost always harmless. Most turn up uninvited, hurt for a few days, and disappear within a week or two without any help at all. A mouth ulcer that won’t heal is a different matter, and there is one simple rule worth knowing: three weeks.
This is written to inform rather than alarm, because the great majority of long-lasting ulcers still turn out to be nothing serious.
On this page
- The three-week rule
- What normal mouth ulcers are like
- Why ulcers happen at all
- Other changes worth getting checked
- What happens if you come in
- Who is at higher risk
- Checking your own mouth
- The bottom line
The three-week rule
An ulcer or sore area in the mouth that has not healed within three weeks should be examined by a dentist or doctor.
That is the whole rule, and it is worth committing to memory. Three weeks is long enough that ordinary ulcers will have resolved, and short enough that anything requiring attention is found early. Getting it checked is not expecting the worst; it is how you make sure of the best.
What normal mouth ulcers are like
Typical ulcers are round or oval, white, yellow or grey in the centre with a red border, and they hurt, particularly with spicy or acidic food. They usually appear inside the cheeks, on the lips or under the tongue, and they heal on their own within one to two weeks.
Recurrent ulcers, arriving in crops every few weeks, are also common and usually benign, though worth mentioning at your check-up so the pattern is on record.
Why ulcers happen at all
Common triggers include:
- Biting your cheek or tongue accidentally
- A sharp tooth, a rough filling or a denture rubbing
- Stress and tiredness
- Hormonal changes
- Certain foods
- Stopping smoking, which can trigger a temporary crop
- Some medications, and occasionally deficiencies in iron, vitamin B12 or folate
That third bullet is worth noting: an ulcer caused by something rubbing will keep recurring in the same spot until the cause is dealt with. A denture edge or a sharp tooth is easily smoothed, and our page on denture adjustment covers the former.
Other changes worth getting checked
Alongside long-lasting ulcers, these deserve an examination:
- Red or white patches in the mouth that persist
- A lump or thickened area in the mouth, on the lip, or in the neck
- Persistent unexplained numbness in the mouth or lip
- Ongoing hoarseness or a change in your voice
- Difficulty swallowing that does not resolve
- An area that bleeds easily without an obvious cause
Most of these have entirely innocent explanations. They are on the list because checking is quick and knowing is better than wondering.
What happens if you come in
The examination itself is quick and completely painless: a careful look at the area under good light, an examination of the rest of your mouth, tongue and throat, and a gentle feel of your jaw and neck.
Most of the time you leave reassured, sometimes with a cause identified and dealt with, such as a rough edge smoothed. Occasionally an area is monitored and re-checked after a set interval, which is a normal and sensible step rather than a worrying one.
Where a change genuinely warrants specialist assessment, an urgent hospital referral is made promptly and you are told exactly what to expect. Screening does not diagnose; it makes sure the right eyes see the right things quickly. Our page on mouth cancer screening explains how this fits into every check-up.
Who is at higher risk
Smoking is the leading risk factor, and heavy alcohol use raises risk further, with the two multiplying each other when combined. HPV is an increasingly recognised factor, particularly towards the back of the mouth and throat, and risk rises with age.
Having said that, mouth cancer does occur in people with none of these, which is precisely why screening at this practice covers every patient at every check-up rather than only those who look higher risk. The NHS page on mouth cancer sets out the risk factors and symptoms in more detail.
If you smoke and have been thinking about stopping, our smoking cessation support is judgement-free and genuinely useful.
Checking your own mouth
Two minutes once a month, in good light with a mirror. Look at your lips inside and out, your gums, the roof of your mouth, inside both cheeks, and your tongue including its sides and underside. Then feel gently along your jaw and down your neck.
You are not trying to diagnose anything. You are simply learning what your normal looks like, so that anything new stands out and gets seen promptly. Alongside your regular check-ups, that is a genuinely effective safety net.
The bottom line
Most mouth ulcers heal within a fortnight and need nothing more than patience. An ulcer that has not healed within three weeks should be checked, along with any persistent patch, lump or unexplained change. Usually it turns out to be nothing, and finding that out takes five minutes.
If something in your mouth has been there longer than three weeks, please ring us on 01255 422506 rather than waiting to see. Our posts on mouth recovery after quitting smoking and gum disease cover two closely related areas of mouth health.
This article is general information rather than personal dental advice. Every mouth is different, so please speak to your dentist about your own teeth.
