Sorely Confused: The Difference Between Cold Sores, Canker Sores, and Chancres

Many types of sores affect your mouth. Three common types have similar names and other features:

These sores may seem similar but they're often confused. However, their differences are important for treatment and prevention.

This article looks at the defining qualities of each type of sore.

   Cold Sore Chancre Canker Sore
Contagious Yes Yes No
Location Around lips Mouth, genitals Inside mouth
Causes HSV-1, HSV-2 Syphilis Various triggers
Qualities Blister-like, painful Round, firm, painless White with red border, painful

Cold Sores (Oral Herpes)

Oral herpes (cold sore)

DermNet / CC BY-NC-ND 

Cold sores (oral herpes) are small, painful blisters. They're mostly found around the lips. Over the course of a week to 10 days, cold sores typically:

  • Erupt
  • Break open
  • Crust over
  • Heal

Most cold sores are caused by the herpes simplex virus 1 (HSV-1). They can also be caused by HSV-2. But that type's more often seen in genital herpes.

Both HSVs are highly contagious. They're most contagious through an active sore. But herpes can be transmitted even when you don't have sores.

It's possible to get an oral herpes infection through sexual activity. But HSV-1 is more often picked up in childhood. For example, a child can get it from a parent's kiss. You can also get oral herpes from infected objects like eating utensils and razors.

Once you're infected with a herpes virus, it stays in your body forever. It may then cause outbreaks from time to time. Antiviral medications can suppress the virus and help prevent outbreaks.

The herpes virus doesn't cause chancres or canker sores.


Cold sores are small, painful, contagious sores on the lips. They're caused by a herpes virus. You can't get rid of the virus, but medications can help prevent breakouts.

Chancre Sores

Image of chancre on tongue

Reproduced with permission from ©DermNet NZ 2022

Chancres are the first stage of a syphilis infection which is a sexually transmitted infection (STI). Syphilis chancres are most often on the genitals. They can also strike the:

  • Mouth
  • Lips
  • Tongue
  • Tonsils
  • Anus
  • Fingers
  • Breasts
  • Nipples

Chancres are round, firm, and usually painless. Because they don't hurt, they often go unnoticed. This is particularly true when they're in the mouth.

Without testing for syphilis, someone can be infected for a long time before noticing symptoms. Chancres clear up with antibiotic treatment for syphilis.

Oral sex plays a large role in the syphilis epidemic. That's due to chancres in the mouth.

Since chancre sounds much like canker, the terms are easy to confuse. But chancres are most often called chancres, while cankers are called canker sores. That can help you keep them straight.


Chancres are contagious but painless sores caused by syphilis. They may be in or around the mouth, on the genitals, or in other locations. Syphilis is treated with antibiotics.

Canker Sores

Canker sores inside of bottom lip

frank600 / Getty Images

Canker sores (aphthous ulcers) are ulcers in the soft tissues inside the mouth. Canker sores are usually round and white with a red border. They can be painful for several days.

Their exact cause is unclear. Triggers may include:

  • Stress
  • Allergies
  • Dehydration
  • A weak immune system
  • Minor mouth injuries
  • Food sensitivities
  • Genetics
  • Hormonal shifts
  • Various nutritional deficiencies (especially folic acid and vitamin B12)
  • Some medications

Canker sores aren't contagious. But they're sometimes tied to contagious illnesses. For example, canker sores are more common in people with acute HIV infection. That's due to their weakened immune system.

Most canker sores don't need treatment. They generally heal on their own in three weeks or less. Serious sores or those that last extra long should be looked at, though.


Click Play to Learn About the Potential Causes of Canker Sores

This video has been medically reviewed by Brian T. Luong, DMD

If you have a canker sore that is especially large, painful, lasts more than three weeks, or comes with a high fever, get medical attention.

Frequent canker sores can alert you to health problems. For example, they may be the first obvious sign of a nutritional deficiency or immune-related problem.


Canker sores are painful, round, white sores inside the mouth. They aren't contagious. Cankers can be triggered by various things. They don't usually need treatment.


Three similar-sounding mouth sores have key differences. Cold sores are around the mouth and caused by a virus. Chancres are in or on the mouth and related to syphilis. Canker sores are always inside the mouth and have many possible causes. It's important to distinguish between the sores for proper treatment and prevention.

A Word From Verywell

If you have a strange sore on or around your mouth, talk to your healthcare provider or dentist. They'll most likely be able to tell you what it is and how to treat it.

Be cautious with close contact, like kissing or sex, in case it's something contagious.

Remember that some sore-causing infections can be transmitted even when you don't have sores. Always practicing safer oral sex can protect you and your partner(s).

Frequently Asked Questions

  • What are common causes of mouth sores?

    Many things cause mouth sores. Some are contagious while others aren't. They include:

  • Is a chancroid the same as a chancre?

    No. A chancroid is a very painful, soft skin ulcer on the genitals and/or throat. It's sexually transmitted by the bacteria Haemophilus ducreyi. Chancroids are rare in the United States.

    Chancres are painless sores caused by a syphilis infection.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Demir FT, Salaeva K, Altunay IK, Yalcın O. An extraordinary case of syphilis presenting with a labial ulcer. Saudi Med J. 2016;37(11):1261-1264. doi:10.15537/smj.2016.11.15674

  3. Workowski KA, Bachmann LH, Chan PA, et al. Sexually transmitted infections treatment guidelines, 2021MMWR Recomm Rep. 2021;70(4):1-187. doi:10.15585/mmwr.rr7004a1

  4. Cedars Sinai. Everything you ever wanted to know about canker sores.

  5. Vaillant L, Samimi M. [Aphthous ulcers and oral ulcerations]. Presse Med. 2016;45(2):215-226. doi:10.1016/j.lpm.2016.01.005

  6. Edgar NR, Saleh D, Miller RA. Recurrent aphthous stomatitis: A review. J Clin Aesthet Dermatol. 2017;10(3):26-36.

  7. National Institutes of Health, U.S. National Library of Medicine: MedlinePlus. Mouth disorders.

  8. Centers for Disease Control and Prevention. Sexually transmitted disease surveillance 2016.

By Elizabeth Boskey, PhD
Elizabeth Boskey, PhD, MPH, CHES, is a social worker, adjunct lecturer, and expert writer in the field of sexually transmitted diseases.