Mouth ulcers (aphthae): how long they last, how to treat them and when an ulcer needs to be seen by a doctor

What are aphthous ulcers and how can you tell them from other changes in the mouth?

Aphthous ulcers are round or oval, shallow and painful ulcers of the lining of the mouth, which most often appear on the inside of the lips and cheeks and on the tongue. When they keep coming back, doctors speak of recurrent aphthous stomatitis, which a review by Akintoye and Greenberg (2014) calls the most common condition causing ulcers of the oral mucosa.

Estimates of how common they are vary: that review gives about 20% of the population, with a range of 5 to 50% across studies, and a Polish review by Ślebioda et al. gives 5 to 20%. In practice, aphthous ulcers affect as many as one person in five. They usually begin in childhood or the teenage years, and roughly one in three people with them has a relative who also gets them.

Aphthous ulcers are not contagious and should not be confused with cold sores, as the UK’s National Health Service (NHS) points out. Multiple ulcers with a fever, especially in a young child, may have a different cause, described below in the part on ulcers in children.

How long do mouth ulcers last? Types of ulcer and healing time

Minor aphthous ulcers usually heal within 1 to 2 weeks and leave no scars. The NHS says that mouth ulcers usually clear up on their own within a week or two, and a review by Edgar et al. (2017) gives 4 to 14 days for minor ulcers.

The rarer forms last longer, and the size limits differ between authors: Rogers (1996) classes ulcers over 5 mm as large, others those over 10 mm. The table is based on the classification in the review by Edgar et al. The name herpetiform ulcers is misleading, because it describes only their appearance, small clusters, and not an infection with the herpes virus.

What causes mouth ulcers?

Aphthous ulcers have many possible triggers, and it is not always possible to point to a single one. The NHS and reviews by Jurge et al. (2006) and Edgar et al. (2017) list above all minor injuries, stress, hormonal changes, deficiencies and some general illnesses.

Some factors can be reduced, for example by smoothing a sharp edge on a tooth or filling or by changing toothpaste. Others, such as a family tendency or hormonal changes, are beyond control, and then the aim is to ease each episode.

• Minor injury: biting the cheek, a sharp edge on a tooth or filling, orthodontic braces, a poorly fitting denture, hard food or brushing too hard.
• Stress and tiredness.
• Hormonal changes, for example in pregnancy.
• Deficiencies of iron, vitamin B12, folic acid or zinc; according to Jurge et al. they affect up to 20% of patients.
• General illnesses: coeliac disease, Crohn’s disease, Behçet’s disease, HIV infection.
• Some medicines, for example non-steroidal anti-inflammatory drugs or nicorandil.
• Giving up smoking, which triggers ulcers in some people.
• Toothpaste containing sodium lauryl sulphate (SLS).

How to treat mouth ulcers at home, and what helps from the pharmacy?

Treating aphthous ulcers eases the pain and may speed up healing, but it does not prevent further recurrences. A 2026 overview of reviews (Al-Aizari et al.) reports that topical corticosteroids and laser shorten the duration of pain and healing, while preventing recurrences remains limited.

The NHS recommends a few simple steps that reduce irritation of the ulcer. Among pharmacy products, the NHS lists antimicrobial mouthwashes, painkillers in the form of tablets, mouthwashes, gels or sprays, corticosteroid lozenges and a saline mouthwash. A pharmacist, and if in doubt a doctor, can advise which of these are available without a prescription in Poland and how to use them.

Toothpaste without sodium lauryl sulphate is a sensible thing to try with recurrent ulcers. A review by Alli et al. (2019), based on 4 small studies, found fewer ulcers, a shorter duration and less pain, although the authors note that further research is needed.

• Use a toothbrush with soft bristles.
• Eat soft food, and drink cool drinks through a straw.
• Avoid very spicy, salty and acidic food, as well as hard snacks such as toast or crisps.
• Avoid very hot and acidic drinks, for example fruit juices.
• Choose a toothpaste without sodium lauryl sulphate (SLS).

Mouth ulcers in a child: aphthous ulcers or a viral infection?

Aphthous ulcers in a child look and heal the same way as in adults, but in young children multiple painful ulcers with a high fever often have a different cause. A typical example is herpetic gingivostomatitis, which according to Medycyna Praktyczna (a Polish medical reference) most often affects children up to the age of 4: it starts with a high fever and red, swollen gums, followed by blisters and painful erosions.

The acute symptoms of this infection last about 5 to 7 days, and the lesions heal in about 2 weeks. The most common complication is dehydration, because the child refuses to eat and drink because of the pain, and this sometimes requires treatment in hospital. Hand, foot and mouth disease, in which mouth ulcers come with a rash on the hands and feet, and herpangina can look similar.

A child with a fever and multiple ulcers in the mouth should be seen by a doctor, and urgently if they are drinking little or passing urine less often. Care is needed with pharmacy products for pain relief: the UK’s MHRA does not recommend salicylate mouth gels for anyone under 16, and the US FDA states that benzocaine products are not used in children under 2. The choice of painkiller for a child is made by a doctor or pharmacist.

Recurrent mouth ulcers: which tests are worth doing?

With aphthous ulcers that recur often or are severe, it is worth having basic blood tests done through your family doctor: a full blood count, ferritin, vitamin B12 and folic acid. A meta-analysis by Mousavi et al. (2024) showed that people with aphthous ulcers more often have vitamin B12 deficiency, low ferritin and low haemoglobin.

Aphthous ulcers can also be a symptom of general illnesses. A review by Nieri et al. (2017) reports that ulcers occur more often in people with coeliac disease, although the link in adults is unclear. In Behçet’s disease, mouth ulcers come with genital ulcers and eye inflammation, which is why the NHS advises seeing a doctor when mouth ulcers occur together with ulcers elsewhere or with painful, swollen joints.

Systemic medicines, which act on the whole body, are used only in severe or resistant cases, and a 2012 Cochrane review did not identify a single effective medicine of this kind. Supplements make sense when tests confirm a deficiency, not as a shot in the dark.

When does a mouth ulcer need a visit to a dentist or doctor?

A mouth ulcer that has not healed for more than 3 weeks needs a visit to a dentist or doctor. This is what the NHS recommends, and the UK’s NICE guideline NG12 treats an unexplained mouth ulcer lasting more than 3 weeks as a reason for urgent investigation. This does not mean that the lesion is cancer, but only an examination can assess it.

A dentist or doctor should also look at any lesion that looks different from ordinary ulcers. Treatment of lesions of the oral mucosa is among the dental services funded by the NFZ, Poland’s National Health Fund, and no referral is needed to see a dentist with an NFZ contract. If you notice any of the signs on the list, contact a dentist or doctor.

• An ulcer that has not healed for more than 3 weeks.
• A lesion that differs from your usual ulcers or lies close to the throat.
• An ulcer that bleeds, becomes increasingly painful or is surrounded by spreading redness.
• Ulcers also on the skin or genitals, or painful, swollen joints.
• A lump, or a red or red and white patch on the lining of the mouth.
• In a child: a high fever, refusing to drink or passing urine less often.

How it works at DentalBlue

At DentalBlue in Białystok, an ulcer that does not heal or keeps coming back in the same place is assessed by a dentist during a visit without pain, which includes a panoramic X-ray, a consultation, an examination and a written treatment plan; in the clinic’s price list it costs 300 zł. If the ulcers are caused by a sharp edge on a filling, the item “Korekta wypełnienia” (filling adjustment) costs 100 zł. The final scope and cost are set by the dentist, and prices may change. When the symptoms point to a general cause, further investigation is carried out by a family doctor or a specialist. The clinic is open Monday to Friday from 8:00 to 20:00 and on Saturdays from 8:00 to 16:00.