Hi, how are you? For years now, I have been confused by cold sores and canker sores. My understanding it that canker sores occur only inside the mouth and are not contagious, while cold sores occur only outside the mouth and are contagious. I have heard that cold sores come from herpes and other sexually transmitted diseases, but am not sure if this is true.

When a person has blisters outside their mouth (usually on the lip or on the areas below their lips), what is it called? I'm not talking about diseases, but just common blisters. Are these called cold sores? Thank you in advance.
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replied April 23rd, 2018
Thank you for asking at Ehealth forum!

I read your question and I understand your concern.
Yes,cold sores is usually due to herpes and very contagious when its oozing while canker sore is usually due to self biting,stress or hormones.

Yes,these blisters which are outside the mouth are called cold sores.
I hope it helps. Stay in touch with your healthcare provider for further guidance as our answers are just for education and counselling purposes and cannot be an alternative to actual visit to a doctor.
Take care
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