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,

Before Alice answers your question, she strongly urges you to see a health care provider as soon as possible [diagnosis is easier when clinical symptoms (lesions) are present] if you have not already done so. This is important because you need to be certain about your genital herpes status so that you can receive appropriate education and treatment, and also get referrals to other health professionals if needed (see archived Alice: Herpes Simplex 2, Genital Herpes, and Herpes transmission?, and also see the Fall 1996 Highlights for more information on herpes and other STDs). In addition, if you are diagnosed with genital herpes or another STD and if you and your girlfriend have had any unprotected sexual activity involving an exchange of bodily fluids since having had oral sex, she needs to visit a doctor as well (see archived Alice - Testing for Asymptomatic Herpes -- for information on herpes tests).

Since Alice has already written in detail about what canker and cold sores are, please refer to other archived Alice for more information (Fever Blisters on Lips, Canker Sores or Herpes?, and Herpes on the Mouth - Contagious?). In a nutshell, canker sores are painful ulcers, or open sores, on the inner membranes of the mouth and cheek which can also 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 Type I virus. 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 will be canker sores, unless you are absolutely certain, you may not be able to tell the difference between a canker sore and a cold sore by sight (Alice knows doctors who have difficulty distinguishing between the two as well -- it can be that tough!). In that case, treat your sore as though it were a cold sore - that it is infected with 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, Alice understands this is not always possible, so she urges you and your partner to follow appropriate precautions every time you have oral-genital sex (i.e., use a latex condom, oral dam, or other barrier device that completely covers the areas of the cold sores to help prevent the transmission of the herpes virus).

If you do have genital herpes and are concerned about how genital herpes may affect your sex life, please read archived Alice - Fever Blisters on Lips / New Herpes Drugs and Testing for Asymptomatic Herpes - for information on prescription and over-the-counter treatments and asymptomatic herpes, respectively. The message Alice wants you to leave with is that you and your partner can still have and enjoy sexual activity as long as both of you adhere to the safer sex precautions mentioned earlier, during BOTH the latent and active infection periods of genital herpes.

Alice

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