Canker Sores vs. Cold Sores

The canker sores herpes connection

Canker sores and cold sores are sometimes confused, but they are not the same thing. The connection between canker sores and herpes is really just the similarity in names, since they both begin with the letter “c” and end in “sores”.  Also similar is the fact that certain things can trigger an outbreak in each, and their proximity to the mouth when active. That’s where the connection ends.

Cold sores, which are caused by the herpes simplex virus, occur mostly on the lips or outside the mouth and rarely, if ever, on the inside of the mouth. Click here  to see some photos of cold sores. Canker sores, on the other hand, occur inside the mouth, usually on the cheeks, but sometimes on the tongue or the back of the throat and even the gums.  Click here  to see some photos of canker sores.

Difference in appearance

Also known commonly as fever blisters, cold sores form a bumpy blister on the skin when the virus is in an active state. In contrast, canker sores form an indented ulcer, looking much like a small crater somewhere inside the mouth.

close-up image of a canker sore close-up image of a cold sore
Canker sore Cold sore (herpes)

Where do they come from?


The herpes virus is transmitted through kissing, sharing utensils or through sexual contact and is often transmitted unknowingly because an active cold sore is not required for the transmission of the virus – the virus sheds cells even when inactive. A large percentage of the population is infected with herpes and many don’t even know it because the virus remains dormant most of the time.

Canker sores are not caused by viruses and are not contagious. Known officially as recurrent aphthous ulcers, but usually called canker sores or mouth ulcers (and sometimes cancher sores or kanker sores), there are several things that trigger their occurrence.

Is there a cure?

In most cases, the herpes virus travels down nerve pathways and ultimately resides in the nerve cluster at the base of the skull. Once it has found its new home, it hijacks the cell-making machinery of the cells it infects and uses it to make new copies of itself.

After it takes up residence in the nerve cluster, it’s permanent. There is no known cure for herpes. So once you have it, unfortunately, you have it for life.

There are, however, some ways to prevent them from activating. Cold sores are often triggered by sun exposure, stress, illness (hence the terms fever blister and cold sore) and certain foods that have high amounts of the amino acid arginine, such as nuts and (say it ain’t so!) chocolate.

With canker sores, you can also prevent their occurrence – to the point that they rarely occur – by simply avoiding those things that are the primary causes . As with cold sores, canker sores are triggered by stress, certain foods (especially citrus), and most toothpastes .

Do they hurt?

It depends upon the person, but typically, cold sores don’t hurt, they’re just annoying and ugly. At the start of a cold sore outbreak, the spot usually tingles and then slowly turns into a blister. With some people the outbreak will cause a feeling of fatigue.

In contrast, canker sores don’t usually have any warning signs when they start, but once they’re in full bloom they do sting when touched – even by your own tongue – or when eating, especially anything salty like potato chips.

How long do they take to heal?

Both canker sores and cold sores take anywhere from a few days to a week or more to heal. There are treatments available that will speed healing, but the best strategy is to take steps to avoid getting them in the first place.

In the case of cold sores, of course, if you can avoid being infected, that’s the ideal strategy. Unfortunately, as mentioned above, that’s not always possible (unless you avoid all contact with other humans) since the herpes virus can be spread without any visible signs on the infected person.

Next: Herpes treatments