Ask a Dentist

Q: What are mouth ulcers?

Mouth with sore on the inside of the lip

A: Mouth ulcers, also known as canker sores, develop as small white or yellow lesions that have a red border. You can get one or multiple at a time. They can show up on your tongue, inside of your cheek, lips, gums and throat area. 

Canker sores tend to be confused with cold sores. While they look similar, canker sores occur inside your mouth while cold sores typically occur outside your mouth. Unlike cold sores, canker sores are not contagious.

It’s not entirely known what causes canker sources, but trauma or injury to your mouth or soft tissues may be one cause. Some people have been known to get canker sores based on food sensitivities, with triggers including spicy, salty or acidic foods. General diet and nutrient-deficiencies could be another trigger in recurring canker sores; vitamin D or iron deficiencies may cause an increased occurrence of canker sores. Others have seen an increase in recurrence with a hormonal shift or when undergoing stressful situations. 

Canker sores usually heal without any treatment in about a week. If they are painful, over the counter medications and an antimicrobial mouth rinse may provide temporary relief.

If you’re not sure you have canker sores or if you’re unsure how you should treat them, ask your dentist. Some sores, like canker sores, are harmless. It’s important to talk to your dentist about any problems that you’re experiencing with your mouth and oral care.