How to heal mouth ulcers (canker sores): how long they last, causes and when to get checked
Mouth ulcers (aphthous ulcers, canker sores) are small, painful sores with a white-yellow centre and a red border, found on the cheek, the inside of the lip or the side of the tongue. Small ulcers usually heal without a trace in 7–14 days. Home remedies ease the pain while they heal. A sore that hasn't healed in two to three weeks, feels hard or doesn't hurt at all should always be examined.
Why do mouth ulcers appear?
- Minor injuries such as biting your cheek, brushing hard or sharp food
- Stress and lack of sleep
- Iron, vitamin B12 or folic acid deficiency
- Certain foods in some people (acidic fruit, chocolate, nuts)
- Hormonal changes
- Systemic conditions such as coeliac disease, inflammatory bowel disease and Behçet's disease (investigated with frequent recurrences)
Easing mouth ulcers at home
- Rinsing with warm salt water several times a day
- Protective gels or pastes from the pharmacy that cover the sore
- Avoiding acidic, spicy and hard foods for a few days
- Using a soft brush; for some people toothpastes without sodium lauryl sulfate reduce recurrences
- A painkiller as directed on the leaflet if pain is significant
Sores caused by teeth or dentures
A sore that keeps coming back in the same place is often caused by a broken tooth edge, a rough filling, a brace bracket or a spot where a denture rubs. In that case it heals once the cause is removed. For a broken tooth see my tooth broke: what to do; for denture sores see dentures and problems with implant dentures.
Which sores should be examined?
| Warning sign | Why it matters |
|---|---|
| A sore that hasn't healed in 2–3 weeks | Other causes need to be ruled out |
| A sore with hard, raised edges, or one that doesn't hurt | Can be an early sign of mouth cancer |
| A white or red patch in the mouth that won't wipe off | Leukoplakia / erythroplakia needs assessment |
| Many ulcers that recur frequently | Vitamin deficiencies and systemic conditions should be investigated |
| Fever, feeling unwell, difficulty swallowing | Viral infection or widespread inflammation |
In people who smoke or drink alcohol, sores in the mouth that don't heal should be watched more carefully. A dental examination includes the soft tissues of the mouth; if needed, you are referred to an oral surgeon or the relevant doctor.
Mouth examination in Beylikdüzü
Dent32 is at Barış Mah., Ginza Lavinya, E-5 Yanyolu No:30 D:179, 34520 Beylikdüzü, Istanbul and is open seven days a week. To book, call or WhatsApp +90 555 011 33 68, or use our contact page. At the examination we share the findings, the options and the approximate cost in writing; you are under no obligation to start treatment afterwards.
Frequently asked questions
How long do mouth ulcers last?
Small ulcers usually heal by themselves in 7–14 days. Larger ones can take longer; any sore lasting more than three weeks should be examined.
Are mouth ulcers contagious?
No. Cold sores, the blisters on the edge of the lip, are caused by a virus and are contagious; the two are different.
What should I do if I get ulcers often?
With frequent ulcers, iron, B12 and folic acid levels and some systemic conditions should be checked; your GP can help. If a tooth is causing irritation, a dentist can fix it.
