Canker Sore on the Tongue, Lips or Gums

Instructor: Ian Lord

Ian has an MBA and is a real estate investor, former health professions educator, and Air Force veteran.

In this lesson we will learn to identify canker sores that appear on the tongue, lips, or gums as well as learn about canker sore causes and treatment.

Canker Sores

Dave woke up this morning with a small but painful bump inside his lip. Annoyed, he tried to take a look in the bathroom mirror and realized it was a canker sore. How does he know, and what can he do to treat it now? What can he do to avoid this happening again? Let's take a look at how to identify a canker sore along with the causes and treatment.


Unfortunately for Dave, he's had enough canker sores in life to know well what they look like. A canker sore appears in the mouth on the tongue, cheeks, or gums as an open ulcer. A common source of confusion is that unlike a cold sore, canker sores do not appear on the surface of the lips, but can occur on the cheeks and tissues inside the mouth near the lips. The sore is white or yellow and surrounded by a bright red area, although as it begins to heal it turns grey. Typically the sore is round or oval in shape and has a well-defined border. It is also known in medical terms as an aphthous ulcer.

Canker Sore
Canker Sore


One of the first things that went through Dave's mind when he noticed the canker sore was concern about some kind of even worse problem. A moment later, he snapped out of it as he remembered that canker sores are not caused by or a sign of cancer and are not the same thing as herpes or cold sores. The actual common causes are far less scary.

A canker sore might be caused by a viral infection, an immune system problem, or some other unknown cause. Dave's canker sore was likely caused by some minor injury to his tongue, lips, or gums such as biting in his sleep. If he brushed his teeth a bit too roughly, that could also cause a sore. Canker sores are common shortly after having dental work done. It's also possible for canker sores to be caused by hormonal changes or stress as well as vitamin deficiencies of iron, folic acid, or B-12.


Whenever Dave gets a canker sore, the problem usually goes away on its own. The pain is often over in a little over a week, approximately 7 to 10 days, but it can take up to three weeks for the canker sore to completely heal. Larger sores typically take longer to heal. While the sore is painful, he avoids eating hot or spicy foods. He continues to brush and floss, but avoids mouthwashes containing alcohol since these can irritate the canker sore. He can rinse his mouth with salt water or a mixture of milk of magnesia and liquid diphenhydramine.

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