If you’ve ever had a mouth ulcer, you’ll know even the smallest sore on your lips, gum, tongue or inside cheek can make eating and talking extremely painful.
Often, these ulcers resolve untreated within one to two weeks.
But recurring mouth ulcers affect up to one in four of us.
Understanding what’s causing them may help you manage and prevent these painful little sores and know when they could be a sign of something more serious.
What are ulcers?
Mouth ulcers are small sores on the inside of your mouth, also known as aphthous ulcers or canker sores.
They are commonly caused by injury—such as biting your cheek or skin snagging on orthodontic braces or a sharp tooth. But as we’ll explore, there can be other causes.
There are three main types of recurring ulcer: minor, major and herpetiform.
Around 80% of ulcers are minor. These are shallow, small (the size of a green pea) and round or oval-shaped, with a yellow or gray center. They usually take no more than two weeks to heal without treatment.
Major ulcers are larger, deeper and irregularly shaped and take weeks or months to heal. These often cause scarring.
Herpetiform ulcers occur in clusters of up to 100 tiny sores (the size of a matchstick head). These can sometimes merge to look like a large ulcer and take two to three weeks to heal.
Herpetiform ulcers can sometimes be mistaken for the sores caused by the herpes simplex virus (cold sores or genital herpes). But unlike herpes, herpetiform ulcers are not contagious.
Why do I keep getting them?
Some people report that ulcers appear during periods of illness or stress.
They can be linked to shifting hormone levels, with some women more likely to get ulcers before each period.
Recurring ulcers can also run in families. Up to one in two people report a family history.
This may be a mix of genetic predisposition coupled with an overactive immune response. This is when your body’s immune system mistakenly attacks the cells lining the inside of the mouth, causing inflammation and swellings that blister and pop.
What about diet?
For some people, repeated bouts of ulcers are a sign they are low in iron, vitamin B12, vitamin C or folate.
So it’s worth talking to a doctor if you suffer from repeated bouts of mouth ulcers—especially if they occur when you’re unusually tired.
Your doctor may organize a simple blood test to help identify the underlying causes and suggest foods or supplements if required.
What else can cause mouth ulcers?
Certain diseases—including celiac disease, inflammatory bowel disease or autoimmune conditions, such as lupus or Sjögren’s—can all cause mouth ulcers.
In some people, certain medications can also trigger or worsen mouth ulcers. These include medications that interact with the immune system, such as chemotherapy, painkillers such as naproxen and ibuprofen, certain antidepressants, and some medications prescribed for heart conditions.
If you notice ulcers soon after beginning a medicine or increasing the dose, speak to your doctor or pharmacist to see if a change in medication is appropriate. Don’t stop a prescribed medication without medical advice.
How to take care of a mouth ulcer
Most mouth ulcers will heal without treatment in a week or two. But to take care of yourself in the meantime, you can:
- rinse your mouth with warm salt water for 30 seconds a few times a day
- avoid irritants such as spicy, sour or acidic food
- avoid brushing with toothpaste that has a strong mint flavor or a common foaming agent, sodium lauryl sulfate
- keep up regular brushing and flossing, using a soft toothbrush and gentle action.
You may also try a medicated mouth gel to help reduce the pain and swelling caused by mouth ulcers and to temporarily numb the area to make eating more comfortable. Speak to your pharmacist or dentist about available options.
When should I see a doctor or dentist?
Typically, recurrent ulcers that heal on their own are not a cause for concern.
But if you notice an ulcer that doesn’t heal after two weeks, get your dentist or doctor to check it to ensure it’s not cancerous. They will look at and feel the area and may take a biopsy (a small sample) or refer you to a specialist.
Most ulcers turn out to be harmless, but early checks matter. Mouth cancer can be treated effectively when identified early.
If an ulcer is unusually large—or you notice other signs such as a lump or swelling, unexplained bleeding, numbness, difficulty swallowing, voice changes or unexplained weight loss—see your dentist or doctor immediately.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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Why do I keep getting mouth ulcers? (2026, October 16)
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