Cold sores vs. canker sores — Oral sex risks?

Originally Published: September 6, 1996 - Last Updated / Reviewed On: June 9, 2008
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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?


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). More importantly, when oral herpes lesions and/or its contents come into direct contact with the genital area through oral-genital sex, genital herpes most likely will 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 were a cold sore — that it is caused by herpes and contagious. It is recommended that the partner with the cold sore(s) abstain from having oral-genital sex with an uninfected partner until the sores have completely healed. However, refraining may not always be possible, so it is suggested that you and your partner use safer sex methods every time you have oral-genital sex (i.e. use an unlubed latex condom, dam, or other barrier that completely covers the areas of the cold sores to help prevent the transmission of the herpes virus).

If you have not already done so, you may want to see a health care provider as soon as possible as diagnosis of genital herpes is easier when clinical symptoms (lesions) are present. This is important because it will help you be certain about your genital herpes status and you can receive appropriate education and treatment. Your health care provider can also give you referrals to other health professionals if needed. In addition, if you are diagnosed with genital herpes or another sexually transmitted infection (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.

Columbia students can make appointments at Primary Care Medical Services by calling x4-2284 or logging into Open Communicator. If you are not a student at Columbia, you can visit your regular health care provider, your local health department's clinic, or a health center such as Planned Parenthood for testing and treatment.

For more information about the distinction between cold sores and canker sores, or if you do have genital herpes and are concerned about how it may affect your sex life, you can read the Related Q&As listed below, including treatments. If you do have genital herpes, you and your partner can still enjoy sexual activity while practicing safer sex during BOTH the asymptomatic and symptomatic periods of genital herpes. Hopefully the confusion around cold sores, and your actual cold sore, are now clearing up,


December 9, 2005


I would like to give you my thoughts and life experience thus far living with genital herpes. It was 22 years ago, I was just eighteen, my husband nineteen. We were not aware of what...


I would like to give you my thoughts and life experience thus far living with genital herpes. It was 22 years ago, I was just eighteen, my husband nineteen. We were not aware of what happened when you had a cold sore and then had oral sex! I can tell you, you get genital herpes and your life is not the same!

I am 41 and live with this every day. You forget about it when you're not having a outbreak, but any trauma, stress, illness of any kind can and will trigger an outbreak. My initial outbreak was violent. I thought I had the flu, my body ached, but I had blisters on my genital area. My doctor diagnosed me with genital herpes just by looking at it!

Both my husband and I were stupified by how I transmitted this awful disease. The doctor helped shed some light on the subject by asking a lot of questions about our sex life. I had just had our first child and was not sleeping with anyone else! My husband often got cold sores and we did not think about what the repercussions of this would be! We were young and ignorant. After my initial outbreak, I remained asymptomatic for a long period of time. Then, when I started having outbreaks again, they were on my butt cheek. I was not sure what it was because of the placement on the skin. I saw my dermatologist and he told me the facts: they can appear on any part of your body. So far, I suppose I am fortunate that they are confined to my butt area and cannot be seen.

The outbreaks affect every aspect of your life! Be careful: know your body and your partner and most of all be SAFE!