Canker Sore vs Cold Sore

Instructor: Julie Zundel

Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

You have a mysterious sore in your mouth. What is it? This lesson will examine two possible culprits: canker sores and cold sores. We will learn about the differences between the two.

The Problem

You wake up and notice a sore inside of your mouth. It's white, circular and it hurts! Is it a canker sore or is it a cold sore? Is there a difference? Let's take a closer look at canker sores and cold sores to see if we can figure out what's going on inside of your mouth!

Canker Sores

Let's start with canker sores, which are circular sores that appear in the mouth under or on the tongue, on the gums, or on the palate. It sounds a lot like what was in your mouth, doesn't it?

Canker sore inside the mouth

Canker sores are not contagious, but they can be painful. There are three main types of canker sores. See table 1 for the differences between the three groups.

Type Appearance Time to Heal
Minor Oval, small 2 weeks
Major Large, irregular shaped 6 weeks
Herpetiform Very small, occurs in clusters 2 weeks

Out of the three, minor canker sores are the most common and hereptiform canker sores are usually only seen in the elderly.

So what causes these weird sores that appear in your mouth? Unfortunately there's not a clear answer to that, since there are lots of possible causes. Many times they form after an injury to the mouth, whether it be a cut from eating something sharp or a biting the side of the cheek. Sometimes canker sores develop when a person experiences stress or if there is a hormonal change. In some cases they form when a person eats a lot of spicy foods. So did you bite your cheek? Did you eat spicy foods? Let's learn about cold sores to see if the description fits that strange little sore in your mouth.

Cold Sores

Unlike canker sores, which can be caused by a variety of things, cold sores are blisters caused by the herpes virus and typically form on the lips. Sometimes they can be found inside of the mouth, in the nose, or on the face, such as on the eyelids. The blisters will eventually burst open, ooze, and then form a scab. The whole process, from blister to scab, lasts about two weeks.

Cold sore

There are two types of herpes viruses that cause the blisters: herpes simplex 1 and herpes simplex 2. Cold sores are caused by the simplex 1 virus and, unfortunately, once you have the virus you will always have the virus. Herpes simplex 1 is contagious and is transmitted through kissing or sharing cups, utensils, or toothbrushes. Herpes simplex 2 causes genital herpes and is transmitted through sexual contact.

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