Canker Sore vs Herpes

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

Two painful, ugly, and uncomfortable sores. You don't want either. But can you distinguish between the two? This lesson tells you where most canker or cold sores appear and what they typically look like.

Unsightly Sores

You go to sleep feeling great. Nothing is wrong. Then the next day you wake up to discover you have an unsightly, red, and painful sore on your lip. You're afraid everyone will see it and think you're an ugly monster. Ever had that feeling? Well what is that sore? Is it herpes? Or is that a canker sore?

Let's learn to distinguish between the two and know for sure. We'll assume that no other possibilities besides these two exist (which isn't actually true).

Identifying Canker Sores

So that sore - is it on the outside of the lip where everyone can see it, or on the inner portion of your lip inside the mouth? If anywhere inside your mouth, like the inside of the cheeks, inside of the lips, and gums, then it's more likely a canker sore.

A canker sore is a non-contagious sore that forms inside the mouth. Canker sores are caused by a local immune system reaction to some sort of trigger such as trauma, food allergies, and nutritional deficiencies. They are often round, small, yellowish-white in color, with a red border. They can occur alone or in multiples. They are painful, and though they heal on their own, they can come back over and over again.

Note the appearance of this canker sore inside the mouth.
Canker Sore

Identifying Cold Sores

Contrast this description with cold sores (fever blisters) caused by the herpes virus. Technically speaking, the herpes virus can cause cold-sore like blisters to appear just about anywhere on the body, including on the skin of the elbows, knees, inside the mouth, and so on. However, they often appear right around the mouth, either right next to the lip, on the margin of the lip-skin border, or slightly more on the lip itself.

Unlike canker sores, cold sores are contagious. The blisters associated with cold sores will erupt and turn red. They are thin-walled blisters filled with a clear fluid that may ooze. The many small blisters may coalesce into one large blister with time.

Once the blisters break and ooze their contagious fluid, a yellow crust will form over where they once stood and a scab may appear as well. The crust/scab will eventually fall off, leaving a pinkish area of skin that will subside with time and should not leave a scar.

Like a canker sores, the cold sore may be painful and it may come back repeatedly, but most people don't suffer from frequent recurrences.

Note the appearance and stereotypical location of a cold sore.
Cold sore

Hopefully you're now well aware as to how to tell the two common forms of sores in and around the mouth, canker sores vs. herpes-induced cold sores.

Lesson Summary

Canker sores are painful, non-contagious sores that appear on the inside of the mouth only. They are commonly small, yellow-white in color, and surrounded by a red border. They heal on their own but can come back over and over again.

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