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

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  • Written By: Laura M. Sands
  • Edited By: Heather Bailey
  • Last Modified Date: 21 September 2019
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Even though different types of oral sores appear to be similar, a cold sore and a canker sore are actually two completely separate conditions. A cold sore, also known as a fever blister, is caused by the contagious herpes virus simplex 1. A canker sore, also known as an aphthous ulcer, is simply an infected but non-contagious open sore that occurs in the mouth or throat. The primary difference between a cold sore and a canker sore is, therefore, that a cold sore is specifically caused by the herpes virus and a canker sore is not.

Canker sores primarily occur as the result of an injury to the mouth area that becomes infected. For instance, biting the inside of the cheek or the tongue may cause skin injury resulting in a small open sore. When this mouth sore becomes infected, it is known as a canker sore. Some of the other initial causes of canker sores may be injury during a dental visit, abrasions caused by braces or brushing the teeth too aggressively and causing damage to the cheeks or gums. A cold sore and a canker sore may both recur throughout a person’s lifetime, but canker sores are not contagious and do not occur due to viral infection.


A cold sore and a canker sore can both be painful to bear. Applying hydrogen peroxide to a sore is one of the most common canker sore home remedies. Applying milk of magnesia several times throughout the day also offers canker sore relief. Canker sore medication sold at most pharmacies may also provide relief while mouth ulcers heal.

Another difference between a cold sore and a canker sore is that cold sores occur mostly on the outside of the mouth and can be passed to others through intimate contact, whereas canker sores occur mostly inside the mouth and do not spread to others. Cold sores can also be spread by touching them with the hand and then touching another person or another part of the body. Even when cold sores are not present, a person is still infected with the herpes virus for life and most experience recurring cold sores as a result.

A cold sore and a canker sore also differ in that there is no cure for the herpes virus. There are antiviral medications that may help limit the recurrence of cold sores, as well as pain medications that can help relieve the nerve pain cold sores sometimes cause. There is no proven way of completely suppressing the herpes virus once a person has become infected, however.

A cold sore and a canker sore are not considered serious conditions. A canker sore will usually go away on its own with or without treatment, as will a cold sore. A cold sore, however, will likely continue to recur periodically throughout a person’s life and may even cause other forms of the herpes virus, such as herpes simplex 2, if active cold sores make contact with the genitalia.



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