Sorely Confused: Differences Between Cold Sores, Canker Sores, and Chancres

People can experience 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: canker sores, the cold sores caused by oral herpes, and chancre sores caused by syphilis.

The last two names are particularly confusing, as chancre rhymes with canker. Sometimes people aren't certain exactly what their doctor has said. You should always ask your doctor to clarify, but understanding the differences between the three is also helpful.

Mouth Sores and Oral STDs

The sores found on the face and mouth are the ones that are usually confused by name. Although chancres can occur on the genitals, cold sores and canker sores are restricted to the face. (Strictly speaking, cold sores are the same as genital herpes sores. However, they are not referred to as cold sores when they are on the genitals.)

Only chancres and cold sores are sexually transmitted and contagious. They are caused by syphilis and herpes, respectively. Canker sores are benign mouth ulcers. They are not contagious. They may be associated with contagious infections, if those infections lead to immune problems.

If you have a strange sore on or around your mouth, talk to your doctor or dentist. They will most likely be able to diagnose the type of sore by looking at it or testing it. Then they can determine how and if the sore should be treated.

If you are uncertain what type of sore you have, it makes sense to be cautious during intimacy with a sexual partner. Several types of sores can be transmitted through kissing and oral sex. Indeed, some of the diseases that can cause these sores may be transmitted even when sores aren't visible.

Practicing safer oral sex can reduce the risk of STD transmission. It may also be possible to reduce the risk of transmitting oral STDs by using disinfectant mouthwash. However, that research is still in its early phases.

Chancre Sores Are Caused by Syphilis

Male syphilis, illustration
Kateryna Kon/Science Photo Library/Getty Images

A chancre is a round, usually painless, sore. Chancres are the first stage of a syphilis infection. Primary syphilis chancre sores are most often found on the genitals. They can also be found on the anus, mouth, lips, tongue, tonsils, fingers, breasts, and nipples.

Chancre sores are not commonly found on the face, although they can be. However, the similarity in names between canker sores and chancre has been known to confuse more than a few people. Fortunately, chancres are most commonly referred to as chancres and not chancre sores.

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.

Unlike cold sores and canker sores, a chancre is usually painless. These sores are caused by syphilis. Syphilis can be treated with antibiotics.

Cold Sores Are Caused by 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. This is the type of herpes 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. This is especially when active lesions are present, although herpes can be transmitted when there are no sores. Herpes can be transmitted by casual as well as sexual contact.

Friendly kissing puts you at risk of cold sores. It's not just anal, vaginal, and oral sex. Herpes transmission may also be associated with exposure to infected objects such as eating utensils and razors. 

Herpes sores of the genitals are not usually called cold sores. That's true even though they're the same sores that appear on the face. Neither canker sores or chancre sores (chancres) are caused by herpes.

Canker Sores Are Not an STD

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 immune 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 and can remain painful for several days. They generally heal within one to three weeks. Most canker sores do not need treatment. However, serious sores should be looked at.

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.

Frequent canker sores may suggest that you are dealing with other health problems. For example, you may not be getting enough of certain nutrients in your diet. You might also have a health problem that affects your immune system—such as HIV. Untreated HIV infection also increases the risk of other mouth sores, including chancres and cold sores.

Sources:

Centers for Disease Control and Prevention (CDC). Transmission of primary and secondary syphilis by oral sex--Chicago, Illinois, 1998-2002. MMWR Morb Mortal Wkly Rep. 2004 Oct 22;53(41):966-8

Chi CC, Wang SH, Delamere FM, Wojnarowska F, Peters MC, Kanjirath PP. Interventions for prevention of herpes simplex labialis (cold sores on the lips). Cochrane Database Syst Rev. 2015 Aug 7;(8):CD010095. doi: 10.1002/14651858.CD010095.pub2

Patton LL. Oral lesions associated with human immunodeficiency virus disease. Dent Clin North Am. 2013 Oct;57(4):673-98. doi: 10.1016/j.cden.2013.07.005

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