Canker Sores vs. Cold Sores: What's the Difference?

That painful spot in or around your mouth could be a canker sore or a cold sore, and while people often confuse the two, they are quite different conditions. Knowing which one you have helps you treat it properly. Here is how to tell them apart.

Canker sores

Canker sores appear inside the mouth, on the soft tissues like the inner cheeks, tongue, or gums. They are small, round ulcers, often with a white or yellowish center and a red border. Importantly, canker sores are not contagious. Their exact cause is not always clear, but triggers can include minor mouth injuries, stress, certain foods, and hormonal changes.

Cold sores

Cold sores, on the other hand, usually appear outside the mouth, most often on or around the lips, as fluid-filled blisters that later crust over. Unlike canker sores, cold sores are caused by a virus and are contagious, spreading through close contact. They often come with a tingling or burning sensation before they appear.

Key differences at a glance

• Location: canker sores inside the mouth; cold sores on or around the lips
• Cause: canker sores are not viral; cold sores are caused by a virus
• Contagious: canker sores are not; cold sores are
• Appearance: canker sores are ulcers; cold sores are blisters

How to treat them

Both usually heal on their own within a week or two. Over-the-counter treatments can ease discomfort, and for cold sores, antiviral options may help if started early. Avoiding known triggers and irritating foods helps too.

When to see a professional

See your dentist or doctor if a sore is unusually large, lasts more than two weeks, keeps coming back frequently, or is severe. Persistent mouth sores should always be evaluated.

Frequently Asked Questions

How can I tell a canker sore from a cold sore?

Canker sores are ulcers inside the mouth and are not contagious. Cold sores are blisters on or around the lips and are caused by a contagious virus.

Are canker sores contagious?

No. Canker sores are not contagious. Cold sores, however, are and can spread through close contact.

When should I see a dentist about a mouth sore?

If a sore is unusually large, lasts more than two weeks, keeps recurring, or is severe, have it evaluated.

If you have a mouth sore that will not heal or you are unsure what it is, reach out to Maricopa Dental Center and we will take a look.