Oral sex with canker sores


Is it safe to have oral sex when either partner has a canker sore — not a cold sore, but a canker sore? Does the same virus cause both and can you cause genital herpes with a canker sore?

— Blister Mouth

Dear Blister Mouth,

Even though canker sores can be quite the annoyance, the good news is they're not contagious nor can they cause genital herpes. Unlike cold sores, which tend to appear on the surface of an individual's lips, these lesions tend to appear more often under an individual's tongue and inside their mouth. Additionally, canker sores can be painful and make eating and talking difficult; however, they usually only last a week or two. Cold sores and canker sores aren't caused by the same virus. In fact, the exact cause of canker sores is still relatively unknown. Some researchers believe that they may be sparked by stress, trauma to the area in your mouth, allergies and sensitivities, bacteria, and certain health conditions and diseases. 

There are different types of canker sores, such as minor, major, and herpetiform sores. Minor canker sores are described as being the most common form of canker sores, and usually are relatively small in size and can take roughly one to two weeks to heal. Major canker sores, on the other hand, are large and deep sores that are very large and very painful. These sores can cause scarring and usually take up to six weeks to heal completely. Finally, herpetiform canker sores, which are relatively rare and usually occur later in life, are very small and tend to form in clusters of up to 100 sores that can eventually merge into one large sore. Despite its name, it's key to note that this form of canker sore isn't caused by the herpes virus infection, so you can't contract herpes from someone who has this kind of canker sore. 

However, if the person performing oral sex does have a canker sore in their mouth, and that individual comes into direct contact with their partner's semen, vaginal fluids, or blood, then they could be increasing their risks of contracting a sexually transmitted infection (STI) from their partner, if they're infected. Any type of lesion or opening in the mucous membrane of the mouth makes transmission of an STI more viable than if the lesion weren't there. You'll need to make decisions about how much risk you want to take with your partner. To reduce your risk of infection, avoiding oral sex when canker sores are present or using a condom or dam during oral sex to protect each other is a good idea.

For more information on canker sores and oral sex, check out the related Q&As. Hope this information helps!

Last updated Jan 07, 2022
Originally published Dec 04, 1995

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