Cold sores vs. canker sores — Oral sex risks?

Originally Published: September 6, 1996 - Last Updated / Reviewed On: October 10, 2014
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Dear Alice,

What's the difference between a canker sore and a cold sore? In your response to Oral sex with canker sores, you replied that it was safe and could not cause an infection of the genital region. My girlfriend had what we thought was a canker sore, and I happened to become infected with what we have assumed to this point is herpes. Would a cold sore cause this or did we just win the lottery with a canker sore?

Sincerely,
ignorant

Dear ignorant,

There is often confusion between canker sores and cold sores. In a nutshell, canker sores are painful ulcers, or open sores, on the inner membranes of the mouth and cheek, or can resemble pimples on the tongue. Canker sores are not considered to be contagious and are of uncertain origin.

Cold sores, on the other hand, are small red blisters that generally affect the mouth and facial areas, but usually appear on the lip and outer edge of the mouth. In contrast to canker sores, cold sores are extremely contagious and are most often caused by the herpes simplex virus type 1 (HSV-1). When oral herpes sores and/or its contents come into direct contact with the genital area through oral-genital sex, genital herpes can develop.

Although it is more likely that the sores that develop in your mouth are canker sores, you may not be able to tell the difference between a canker sore and a cold sore by sight. If you're unsure, it's wise to treat your sore as though it is a herpes sore and contagious. It’s usually a good idea for any partner who currently has sores to abstain from having sex until they have completely healed. However, herpes can be transmitted when a sore is not present through viral shedding. When engaging in sexual activity, it might be best for you and your partner to use safer sex methods every time you have sex (oral or otherwise). These can include using a male or female condom, a dam, or other barriers that completely cover the areas with sores to help reduce the chances of transmission of the herpes virus or any other sexually transmitted infections (STIs).

If you have not already done so, consider seeing a health care provider as soon as possible — a diagnosis of genital herpes is easier when symptoms (sores) are present. Doing this will allow you to be certain about your herpes status, give you time to ask additional questions, and receive appropriate treatment. In addition, if you are diagnosed with genital herpes or another STI, and if you and your girlfriend have had any unprotected sexual activity involving skin-to-skin contact and/or an exchange of bodily fluids since having had oral sex, it is recommended that she visit a health care provider for an examination, as well.

Check out the related Q&As below to learn more about the distinction between cold sores and canker sores and managing herpes. Hopefully the confusion around cold sores, and your actual cold sore, is now clearing up!

Alice

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