Sorely Confused - Cold Sore, Canker Sore, Chancre?

What is the Difference Between Cold Sores, Canker Sores, and Chancre?

People suffer from an array of sores on their mouths and their genitals. Three of these types of sore are, by virtue of their name and location, frequently confused. These are canker sores, the cold sores caused by oral herpes, and the chancre sores caused by syphilis. (It doesn't help that chancre rhymes with canker so sometimes people aren't certain exactly what their doctor has said.)

1
Cold Sores - Herpes

Girl with cold sore
Peter Dazeley/Photographer's Choice RF/Getty Images

Cold sores, or fever blisters, are caused by a herpes virus. These small painful blisters are most often found around the lips. They usually break open, crust over, and heal over the period of a week to 10 days. Cold sores are usually caused by HSV-1, the type of virus most often associated with oral herpes. They can also be caused by HSV-2, which is more often associated with genital herpes. Both types of herpes virus are extremely contagious, especially when active lesions are present. They can be transmitted by casual as well as sexual contact. In other words, friendly kissing puts you at risk as well as anal, vaginal, and oral sex. Herpes transmission may also be associated with exposure to infected objects such as eating utensils and razors. It can even happen when no symptoms are present.

Summary: Herpes causes cold sores. It does not cause chancres or canker sores. 

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2
Canker Sores

Multiple canker sores in a person with HIV.. Photo Courtesy of CDC/Sol Silverman, Jr., DDS (1999)

Canker sores are ulcers that occur in the soft tissues inside your mouth. They are associated with various nutritional and immunological deficiencies. Unlike cold sores, canker sores are not STDs. They are neither contagious nor sexually transmitted. They are, however, more common in individuals with acute HIV infection. That's because of HIV's negative effects on the immune system.

Canker Sores are also known as aphthous ulcers. They are usually round white sores with a red border. Canker sores can remain painful for several days but generally heal within one to three weeks. If you have a canker sore that is particularly large, uncontrollably painful, lasts longer than three weeks, or accompanied by a high fever, seek the attention of a healthcare practitioner.

Summary: Canker sores are not STDs. They are, however, more common in people who are immunocompromised. Untreated HIV infection can lead to an impaired immune system and make them more likely. 

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3
Chancres - Syphilis

Examples of the chancre, or sore, typical of a primary syphilis infection.. Photos courtesy of the CDC/Dr. Gavin Hart; Dr. N.J. Fiumara; Dr. Dancewicz

The round, usually painless, sore that is the first stage of a syphilis infection is known as a chancre. Although not usually found on the face, the similarity in names between "canker sores" and "chancre" has been known to confuse more than a few people. Primary syphilis chancres are most often found on the genitals. They can also be found on the anus, mouth, lips, tongue, tonsils, fingers, breasts, and nipples.

Because chancres are painless, they often go unnoticed. This means that, without testing, some people can be infected with syphilis for a long time before they notice any symptoms. This is particularly true when chancres occur within the mouth. Chancres in the mouth are one reason that transmission through oral sex has made a significant contribution to the syphilis epidemic over the past few years.

Summary: Chancres are caused by syphilis, not herpes or another STD. They are usually painless. Syphilis can be treated with antibiotics. 

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