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What Is the Difference Between a Cold Sore and a Canker Sore?

Both cold sores and canker sores develop in and around the mouth. Cold sores are caused by a herpes virus and are extremely contagious, whereas canker sores are noninfectious. However, cold sores are blisters, while canker sores are ulcers.

How to Tell Them Apart

While cold and canker sores might feel the same when the painful lesions appear in your mouth, they have slightly different symptoms. The signs of cold sores include:

  • Painful clusters of blisters on the lips, gums, tongue, and roof of the mouth, usually only on one side of the mouth
  • Itching and burning at the sore sites
  • Fluid oozing from the sores, which later become crusty

Signs of canker sores include:

  • Small, painful ulcers on the tongue, roof of the mouth, and inside of the cheeks
  • Tingling and burning at the sore sites
  • Round lesions that are white or off-white with reddish borders

One of the key differences between cold and canker sores is that canker sores typically only develop inside the mouth, whereas cold sores can also show up around the lips.

The Causes of Cold vs. Canker Sores

Cold sores are typically caused by herpes simplex virus type 1 and, less commonly, type 2. You can get the virus from kissing or engaging in oral sex with someone who has open sores. Once you’re infected with the virus, you carry it for life. The sores usually only pop up when the immune system is weak due to things like illness or stress.

Canker sores are not sexually transmitted. Rather, they commonly result from biting your inner cheek or tongue, rough dental work, acidic foods, allergies, and more. Some people might be genetically predisposed to developing canker sores. Others experience outbreaks as a result of triggers such as stress, nutrient deficiencies, and hormone fluctuations.

Both cold and canker sores resolve on their own within about a week or two.

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