Mouth ulcers are painful sores that appear in the mouth. Although they’re uncomfortable, they’re usually harmless and most clear up by themselves within a week or two. They commonly appear inside the mouth on the cheeks, lips, or tongue and they can be white, red, yellow, or grey in colour and swollen. It’s possible to have more than one mouth ulcer at a time and they may spread or grow.
Mouth ulcers shouldn’t be confused with cold sores, which are small blisters that develop on the lips or around the mouth. Cold sores often begin with a tingling, itching, or burning sensation around your mouth.

The exact cause of most mouth ulcers is unknown. Stress or tissue injury is thought to be the cause of simple mouth ulcers. Certain foods, including citrus or acidic fruits and vegetables (such as lemons, oranges, pineapples, apples, figs, tomatoes and strawberries), can trigger a mouth ulcer or make the problem worse. Sometimes a sharp tooth surface or dental appliance, such as braces or ill-fitting dentures, might also trigger mouth ulcers.

Pain from a mouth ulcer generally lessens in a few days and the sores usually heal without treatment in about a week or two. Rinsing with salt water can also help disinfect and clear them up quickly although this can cause some stinging. If sores are large, painful, or persistent, your dentist may recommend an antimicrobial mouth rinse, a corticosteroid ointment, or a prescription or non-prescription solution to reduce the pain and irritation.

Although there is no cure for mouth ulcers, and they often reoccur, you may be able to reduce their frequency with good dental hygiene and by:

• Avoiding foods that irritate your mouth, including acidic or spicy foods
• Avoiding irritation from gum chewing
• Brushing with a soft-bristled brush after meals and flossing daily, which will keep your mouth free of foods that might trigger a sore.

If your mouth ulcer doesn’t clear up in a week or two seek medical advice.