May also be called: Canker Sores; Oral Aphthae; Aphthous Stomatitis

Apthous ulcers, or canker sores, are small ulcers that occur inside the mouth, often causing discomfort during eating or talking. They are not contagious and not associated with cold sores that appear outside the mouth.

More to Know

No one knows exactly what causes apthous ulcers, but many factors put a person at risk for getting them. Diet; emotional stress; nutritional deficiencies of folic acid, vitamin B12, or iron; and food allergies can all contribute.

Mouth injuries, such as biting the inside of the lip or brushing too hard, also can bring on the sores. Sometimes apthous ulcers indicate a person has an immune system disorder or other health condition.

Anyone can get apthous ulcers, but teens and people in their early twenties are affected the most.

Keep in Mind

Although painful, apthous ulcers are generally not serious and can be easily treated with over-the-counter or home remedies.

If the sores last longer than 2 weeks, occur often, are associated with fever or other symptoms, or make it hard to eat and drink because of the pain, contact your doctor.

All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.