Canker vs. Cold Sore. Canker sores (aphthous ulcers) and oral herpes (cold sores) are two distinct types of lesions. Unfortunately many patients and even some dentists commonly refer to them interchangeably and do not fully understand the differences and causes. Here is a good resource for clarification: http://publications.Usa.Gov/epublications/fever-blister/fever-canker.Html.
No. Canker sores aren't herpes; cold sores are. (herpes are on the lips, but not usually inside the mouth.).
Canker sores. Canker sores are not herpes, but cold sores are herpes simplex type 1 and very contagious. Stress, citrus fruits, impaired immune system can cause canker sores , usually last a week or two.. Cold sores last longer and have fluid-filled blisters, cause by virus and usually appear outside of the mouth.