Last updated: July 2026. Information sourced from NHS.uk, the NHS Business Services Authority (NHSBSA), the British Dental Association (BDA), GOV.WALES and Healthwatch. NHS dental charges confirmed from 1 April 2026.
TL;DR: A dental abscess is a pus-filled infection around a tooth or gum that causes swelling, throbbing pain and sometimes fever, and it never clears on its own. A mouth ulcer is a soft sore on the cheek, lip or tongue that usually heals within one to two weeks. An abscess needs urgent dental care, an ulcer rarely does.
You have found a sore, a lump or a painful spot in your mouth, and you are trying to work out whether it is something that will settle on its own or something that needs a dentist today. The distinction matters more than most people realise. A mouth ulcer is usually harmless and self-healing, while a dental abscess is a spreading bacterial infection that, left untreated, can become genuinely dangerous.
This guide explains how to tell a dental abscess from a mouth ulcer, the red-flag signs that mean you should seek urgent care, how each is treated on the National Health Service (NHS), and what treatment costs across the UK in 2026.
Abscess or Ulcer? The Quick Answer
The single most reliable way to tell them apart is location and what surrounds the sore. A dental abscess centres on a tooth or the gum right beside a tooth, and it produces swelling, pus and often whole-body symptoms such as a raised temperature [1]. A mouth ulcer sits on the soft lining of the mouth, most often the inside of the cheeks, the lips or the tongue, and it does not cause facial swelling or fever [2].
A dental abscess is defined by the NHS as "a build-up of pus in the teeth or gums caused by an infection", and it "will not go away on its own" [1]. That last point is the crucial one. If your symptoms are getting worse by the hour rather than slowly easing, you are far more likely to be dealing with an abscess than an ulcer.
A mouth ulcer, by contrast, "should clear up on their own within a week or 2" and is not contagious [2]. Ulcers are painful, especially when you eat something spicy, salty or acidic, but the pain stays local to the sore and does not come with the swelling or fever that mark an infection.
Dental Abscess vs Mouth Ulcer: Side-by-Side Comparison
Use this table as a quick reference. If your symptoms line up with the abscess column, treat it as urgent and contact a dentist. If they match the ulcer column and have lasted less than three weeks, self-care is usually enough.
| Feature | Dental abscess | Mouth ulcer |
|---|---|---|
| What it is | Pus from a bacterial infection in or around a tooth [1] | A sore on the soft lining of the mouth, not usually an infection [2] |
| Typical location | At the root of a tooth or in the gum beside it; swelling can spread to the face or jaw [1] | Inside the cheeks, on the lips or on the tongue [2] |
| Appearance | Redness inside or outside the mouth, visible swelling, sometimes pus [1] | A round or oval sore with a pale centre and a red border |
| Pain | Intense, throbbing toothache or gum pain; sensitivity to hot and cold; worsens over time [1] | Soreness that flares when eating spicy, salty or acidic food [2] |
| Whole-body signs | Bad taste, swollen face or jaw, swollen neck glands, high temperature [1] | None expected for a straightforward ulcer [2] |
| Does it clear on its own? | No, needs urgent dental treatment [1] | Usually yes, within one to two weeks [2] |
| When it is urgent | Facial swelling, trouble breathing, swallowing or opening the mouth, eye involvement [1] | Lasting more than three weeks, unusually large, bleeding or near the throat [2][3] |
What a Dental Abscess Looks and Feels Like
A dental abscess builds when bacteria reach the inside of a tooth or the gum tissue around it, usually through tooth decay, gum disease, a cracked tooth or an injury [1]. The infection produces pus, and because that pus has nowhere to drain, pressure builds and the pain intensifies.
The NHS lists the typical symptoms of a dental abscess as intense toothache or gum pain, redness inside the mouth or on the face and jaw, sensitivity to hot and cold, a bad taste in the mouth, difficulty opening the mouth and chewing, a swollen face or jaw, swollen glands in the neck, and a high temperature [1]. You will not usually have all of these at once, but the combination of localised tooth pain with swelling is the classic signature.
There are two main types. A periapical abscess starts inside the tooth, at the root, and is typically linked to decay or a dying nerve. A periodontal (gum) abscess forms in the gum pocket beside a tooth root and is more often linked to gum disease, which is why it can look like a distinct, tender lump on the gum rather than a sore on the cheek. If you want the full picture on how these are diagnosed and treated, our guide to dental abscess symptoms, treatment and NHS costs goes into more depth, and our gum disease treatment guide covers the periodontal side.
What a Mouth Ulcer Looks and Feels Like
A mouth ulcer is a small break in the soft lining of the mouth. Most are caused by minor trauma such as biting the inside of your cheek, catching the gum with a toothbrush, a sharp tooth or a rough filling, or a burn from hot food or drink [2]. Stress, tiredness, hormonal changes and certain vitamin deficiencies can also trigger them.
Ulcers commonly appear on the inside of the cheeks or lips, and can also form on the tongue [2]. A typical ulcer is round or oval with a pale white, grey or yellow centre and a red inflamed border. Most people get one to a few at a time, and they are sore rather than throbbing.
The reassuring news is that the vast majority of ulcers heal by themselves. The NHS advises using a soft-bristled toothbrush, drinking cool drinks through a straw, eating softer foods, and avoiding spicy, salty, acidic, rough or very hot food and drink while it heals [2]. A pharmacist can recommend an antimicrobial mouthwash, a painkilling gel or spray, or corticosteroid lozenges to ease the discomfort. Our full guide to what causes mouth ulcers and when to see a dentist covers the self-care routine in detail.
The Red Flags: When It Is Serious
This is the part to read carefully. Both conditions have specific warning signs, set out by the NHS, that change the situation from "manage at home" to "get help now". Knowing these exact triggers is the single most useful thing you can take from this article.
When a Dental Abscess Becomes an Emergency
A dental abscess always needs treatment, but certain signs mean the infection may be spreading and you need emergency care rather than a routine urgent appointment. The NHS says to call 999 or go to accident and emergency (A&E) if you [1]:
- are finding it hard to breathe, speak or swallow
- have a swollen or painful eye, or suddenly start having problems with your eyesight
- have a lot of swelling in your mouth
- are finding it hard to open your mouth
If you have none of those emergency signs but think you have an abscess, the correct route is still urgent. The NHS advises you to ask for an urgent dentist appointment or get help from NHS 111 [1]. Call your own dentist first, and if the practice is closed, call 111 or use 111 online, which can direct you to where you can be seen.
Do not go to your GP for an abscess. A general practice cannot provide dental treatment such as drainage, so the right routes are your dentist, an emergency dentist or NHS 111, never a GP appointment [1]. A&E can help with a life-threatening emergency like swelling that affects breathing, but it cannot drain a routine abscess either.
When a Mouth Ulcer Needs Checking
Most ulcers need nothing more than patience. The NHS advises you to see a dentist or GP if your mouth ulcer [2]:
- lasts longer than three weeks
- is different to other mouth ulcers you have had before, for example if it is bigger than usual or near the back of your throat
- bleeds or becomes more painful and red, which may be a sign of an infection
The three-week rule is the most important safety message in this whole article. An ulcer or sore that has not healed after three weeks is one of the listed symptoms of mouth cancer, alongside red or white patches in the mouth, unusual lumps, and unexplained loose teeth [3]. These symptoms usually have a far less serious cause, but they should always be checked, because mouth cancer is far more treatable when caught early. Our guide to mouth cancer symptoms and when to see a dentist explains what to look for.
Can a Mouth Ulcer Turn Into an Abscess?
No, a mouth ulcer does not turn into a dental abscess. They affect different tissues and are different disease processes. An ulcer is a break in the soft lining of the mouth, while an abscess is a pocket of bacterial infection at the root of a tooth or in the gum around it [1][2]. One does not become the other.
Two situations do cause genuine confusion, though. A sore or ulcer right at the gumline next to a tooth can be mistaken for early gum-abscess swelling, and vice versa. And a sore that keeps recurring in the same spot, or that does not heal, is exactly the kind of change the NHS says to get checked [2][3].
The safest approach is simple. If a sore does not fit the normal ulcer pattern, if it is bigger, redder, bleeding, unusually painful, or has lasted more than three weeks, treat it with the same urgency as suspecting an abscess and get it looked at. You do not need to diagnose it yourself. That is your dentist's job.
How Each Is Treated on the NHS, and What It Costs
Treatment for the two conditions could hardly be more different, and so is the cost. A dental abscess needs a hands-on dental procedure, while a mouth ulcer rarely needs more than a trip to the pharmacy.
Treating a dental abscess
The essential point is that a dentist has to physically drain the infection, whether by draining the abscess itself, carrying out root canal treatment to save the tooth, or removing the tooth [1]. Painkillers such as ibuprofen or paracetamol can ease the discomfort while you wait, but they do not treat the underlying infection.
Antibiotics alone do not cure a dental abscess. The NHS is explicit that repeated antibiotics without drainage are ineffective at preventing the infection from spreading, and antibiotics are used only where there are signs of severe or spreading infection [1]. The BDA reinforces the same message in its public-health campaigns: the fix for toothache and dental infection is a dental procedure, not simply a prescription [8]. A dentist may prescribe antibiotics alongside drainage in specific cases, but never as a substitute for it.
Treating a mouth ulcer
Most ulcers need only self-care and, if the pain is bothersome, a pharmacy product [2]. You would see a dentist or GP only if the ulcer meets one of the red-flag triggers above, in which case they may prescribe something stronger or investigate a non-healing sore. There is no set NHS charge for ulcer advice from a pharmacist, so for most people a mouth ulcer costs nothing to manage.
NHS dental charges in England (2026)
If you need an abscess treated on the NHS in England, the cost depends on what the dentist does. Crucially, urgent NHS dental treatment, which includes abscess drainage, is charged at the Band 1 rate, not a separate emergency premium [4][5].
| Treatment | NHS band | Cost (from 1 April 2026) |
|---|---|---|
| Urgent care, including abscess drainage | Band 1 (urgent) | £27.90 |
| Root canal treatment or extraction | Band 2 | £76.60 |
| Crown after root canal, if needed | Band 3 | £332.10 |
You pay only one charge per complete course of treatment, even if it takes more than one appointment [4]. For the full picture on how the banding works and which treatment falls into which band, see our NHS dental charges guide.
Costs differ across the UK
The bands above apply to England only. The other UK nations charge differently, so do not assume the England figures apply where you live. In Wales, NHS dental charges moved to a fixed fee per care package from 1 April 2026, capped at a maximum of £384 per course of treatment, with an urgent care package costing £37.50 [9]. In Scotland and Northern Ireland, patients generally pay a percentage of the treatment cost, capped at £384 per course, with free examinations for everyone in Scotland. Check your nation's official NHS or government page for the exact figure.
Free NHS dental treatment
You may not have to pay at all. You qualify for free NHS dental treatment in England if you are under 18, or under 19 and in full-time education, pregnant or have had a baby in the last 12 months, or if you receive certain benefits such as income-related Employment and Support Allowance, Pension Credit Guarantee Credit, or Universal Credit with earnings below the qualifying threshold [6]. Holding a valid HC2 certificate under the NHS Low Income Scheme also gives full help with costs. Our free NHS dental treatment eligibility guide sets out every category.
How to Get Urgent Dental Care Without a Regular Dentist
You do not need to be registered with a dentist to get urgent care. If you think you have an abscess and do not have a regular dentist, the NHS route is to get advice from NHS 111, by phone on 111 or online at 111.nhs.uk, or to contact a dental practice directly and ask for an urgent appointment [7]. You should be offered urgent dental treatment within a timeframe that depends on your symptoms.
This matters because NHS dental access is genuinely difficult for many people right now. A Healthwatch survey published in March 2026 found that 32% of people in England used private dentistry in the past year, up from 22% in 2023, and that people in more deprived areas were almost twice as likely to have gone private because they could not find an NHS dentist [10]. If you are struggling to get seen, our emergency dentist guide explains every route to urgent care, and our toothache relief guide covers what you can do to manage pain while you wait.
Frequently Asked Questions
How do I know if it is an abscess or an ulcer?
Check the location and the surrounding signs. An abscess sits at a tooth or the gum beside it and brings swelling, throbbing pain and sometimes fever or a bad taste. An ulcer is a sore on the soft cheek, lip or tongue with no swelling or fever, and it usually heals within two weeks.
Can a mouth ulcer turn into a dental abscess?
No. A mouth ulcer and a dental abscess affect different tissues and are different conditions, so one cannot become the other. An ulcer is a soft-tissue sore, while an abscess is a bacterial infection around a tooth. However, any sore that does not heal within three weeks should always be checked by a dentist.
How long before a mouth sore is serious?
A mouth ulcer that lasts longer than three weeks should be seen by a dentist or GP, because a non-healing sore is a listed symptom of mouth cancer. A dental abscess is serious from the start and needs urgent care, especially if you have facial swelling or difficulty breathing, swallowing or opening your mouth.
Will a dental abscess go away on its own?
No. The NHS is clear that a dental abscess will not clear up without treatment, because the infection has no way to drain by itself. It needs a dentist to drain it, carry out root canal treatment, or remove the tooth. Painkillers only ease the symptoms and do not treat the infection.
Do I need antibiotics for a dental abscess?
Not on their own. Antibiotics alone do not cure a dental abscess, because they cannot drain the infection. The NHS and the BDA both stress that the real fix is a dental procedure. A dentist may prescribe antibiotics alongside drainage where the infection is severe or spreading, but never as a replacement for treatment.
How much does it cost to treat a dental abscess on the NHS?
In England, urgent NHS dental treatment including abscess drainage is charged at the Band 1 rate of £27.90 from April 2026. If you need root canal treatment or an extraction, that falls under Band 2 at £76.60. You pay only one charge per course of treatment, and many people qualify for free NHS dental care.
Should I go to A&E for a dental abscess?
Only for a life-threatening emergency. Go to A&E or call 999 if you are finding it hard to breathe, speak or swallow, have a lot of swelling in your mouth, cannot open your mouth, or have eye swelling or vision problems. For a routine abscess without those signs, contact your dentist or NHS 111 instead, as A&E cannot drain it.
Finding Help
A mouth ulcer and a dental abscess can feel similar in the first anxious moment, but they call for very different responses. An ulcer usually needs patience and gentle self-care, while an abscess needs a dentist promptly and never resolves on its own. When in doubt, use the red-flag lists above, and remember the three-week rule for any sore that will not heal.
Worried about a sore or a swollen, painful tooth? Search for a dentist near you on Dentists Closeby and find a GDC-registered practice that can see you.
Sources
- Dental abscess -- NHS.uk, reviewed 18 March 2026, accessed 2026-07-13
- Mouth ulcers -- NHS.uk, reviewed 11 March 2024, accessed 2026-07-13
- Symptoms of mouth cancer -- NHS.uk, reviewed 19 June 2023, accessed 2026-07-13
- How much NHS dental treatment costs -- NHS.uk, reviewed 13 March 2025, accessed 2026-07-13
- NHS dental charges poster, April 2026 -- NHSBSA, April 2026, accessed 2026-07-13
- Who can get free NHS dental treatment -- NHS.uk, reviewed 11 February 2025, accessed 2026-07-13
- How to find an emergency or urgent NHS dentist appointment -- NHS.uk, reviewed 14 May 2025, accessed 2026-07-13
- Antibiotics do not cure toothache -- British Dental Association, accessed 2026-07-13
- NHS dental charges and exemptions -- GOV.WALES, current as at 1 April 2026, accessed 2026-07-13
- People struggling financially are hardest hit by the shortage of NHS dental appointments -- Healthwatch England, 9 March 2026, accessed 2026-07-13
