Are Canker Sores Contagious?

Medically Reviewed on 3/6/2023
Are Canker Sores Contagious?
Canker sores are not spread by person-to-person transmission.

Canker sores are not contagious. There is no person-to-person spread. Canker sores seem to develop in an individual when certain triggers occur (such as hormonal shifts, stress, or exposure to certain foods or chemicals). Individuals that develop canker sores may not have the same triggers that cause canker sores to develop in other people.

What is the number one cause of canker sores?

Canker sores are small painful ulcers in the mucous membranes that form the inner lining of the mouth. The cause of canker sores is unclear; no viral or bacterial cause has been proven. Researchers think that they occur or are triggered to occur in individuals when a certain set of circumstances arise such as:

  • emotional stress,
  • hormonal changes,
  • allergies,
  • certain diseases (including Crohn's disease and celiac disease),
  • a lack of certain nutrients and vitamins,
  • sensitivity to certain chemicals in foods or drinks, or
  • even minor trauma while tooth brushing or other minor mouth trauma.

Canker sores can recur. Canker sores are sometimes confused with cold sores, but cold sores are due to herpes viruses and are contagious, while canker sores are not contagious and usually do not involve the lips.

Canker sores also are referred to as:

  • aphthous ulcers,
  • aphthous stomatitis,
  • recurrent aphthous stomatitis, and
  • ulcerative stomatitis.

Are canker sores caused by an STD?

Canker sores are not a sexually transmitted disease (STD). STDs are infections spread through sexual contact, such as vaginal, anal, or oral sex. While STDs can cause sores or ulcers on or around the mouth or throat, these sores are different than canker sores in their appearance and required treatment.

Can canker sores spread?

Canker sores do not spread from person to person. Canker sores are recurrent and may seem to spread in an individual if the mechanisms that trigger canker sore development recur frequently in an individual.

What are the canker sore symptoms?

Shallow painful ulcers with a reddish border are characteristic of canker sores. They may appear on the soft palate, tonsil areas, tongue, and gums of the mouth.

There are three types of canker sores, which include:

  1. Minor canker sores are usually smaller than 1 cm in diameter and account for about 80% of all canker sores.
  2. Major canker sores are greater than 1 cm in diameter, and usually have irregular borders, and when they heal, the ulcers can leave scars and even distort the shape of the mucosal surface.
  3. Herpetiform canker sores are small - no larger than 1 mm - and usually occur in clusters (about 10–100 ulcers). Herpetiform canker sores are poorly named as they do not contain herpes viruses.


Mouth Problems: TMJ, Canker Sores, Painful Gums and More See Slideshow

Why is a canker sore so painful?

Canker sores are small, painful ulcers inside the mouth. They are often painful because they affect the sensitive lining of the mouth, which contains nerve endings. Sores cause inflammation, irritation, and nerve stimulation that typically results in discomfort or pain.

What gets rid of canker sores fast?

There is no known cure for canker sores. The only treatment is for the painful symptoms. However, most minor canker sore problems last about 7 to 10 days while major canker sores may last weeks to months and may cause scars.

When should I contact a doctor about canker sores?

Most minor canker sores do not require a doctor to treat them. However large canker sores (major canker sores) should be seen by a healthcare professional. In addition, rapidly reoccurring sores (new canker sores occurring before older sores heal), sores that persist longer than two weeks, sores that cause problems with either eating or drinking, and sores associated with high fevers should be seen urgently by a physician.

Medically Reviewed on 3/6/2023
Mirowski, GW., MD. "Aphthous stomatitis." Medscape. UPdated: Mar 21, 2017.