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Health Conditions & Illnesses

Are Canker Sores Contagious?

My girlfriend has canker sores. Can I catch them from her?

No. Canker sores are not contagious. Unlike cold sores, you can’t catch canker sores from another person.

Canker sores are a kind of ulcer inside the mouth. No one knows exactly what causes them, or why some people get them and others don’t. Some experts think that canker sores might be caused by injuries to the inside of the mouth (like biting the inside of your cheek) or that they may be brought on by things like stress.

So how can you tell if a sore is a (non-contagious) canker sore or a contagious cold sore? Cold sores usually develop outside the mouth, around the lips, chin, or nostrils. Canker sores are different: they only develop on the inside of the mouth.

Canker sores go away on their own after a while and usually don’t need treatment. But if your girlfriend gets canker sores often, is in a lot of pain, or the sores don’t improve within 2 weeks, she should see her doctor.

Reviewed by: Elana Pearl Ben Joseph, MD
Date reviewed: January 2013

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