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Canker Sore Symptoms: Are Canker Sores Contagious?

Story at-a-glance

  • Canker sores are round or oval lesions that are either white or yellow, and are surrounded by red and inflamed soft tissue
  • It’s a known fact that the duration of canker sores is quite short, with most sores going away on their own in one to two weeks

Knowing what canker sores look like and where they develop can make a big difference. Although canker sores are not contagious1 and often heal quickly, there are instances wherein prolonged nontreatment can actually be detrimental for your health.

Common Symptoms of Canker Sores

Canker sores can be easily spotted because of their appearance. These are round or oval lesions that are either white or yellow,2 and are surrounded by red and inflamed soft tissue.3 You may find them in the following areas:4

Inside your mouth, particularly inside the cheeks or lips

Under your tongue

Base of your gums

Soft palate, or that area on the roof of your mouth composed of muscles5

Canker sores can develop in stages. Before these painful lesions appear, patients often feel a tingling or burning sensation that lasts for at least one to two days.6 Some people also experience symptoms (although uncommon) such as fever, general discomfort or uneasiness (malaise), or swollen lymph nodes.7

When to Have Your Canker Sores Checked

It’s a known fact that the duration of canker sores is quite short, with most sores going away on their own within one to three weeks.8 However, certain abnormalities that might be a sign of other diseases may arise alongside canker sores, so you should consult your physician if you notice these indicators:9

Oddly large canker sores

Recurring sores, wherein new ulcers develop before old lesions completely heal

Frequent outbreaks of canker sores

Canker sores that last for two weeks or more

Canker sores that extend to the lips

Uncontrollable pain even if self-care methods have already been applied

Eating or drinking difficulties

High fevers that occur alongside the sores

If sharp tooth surfaces or dental appliances have caused the canker sores, consult your dentist to check for remedies that may alleviate the pain.10

When it comes to diagnosing canker sores, a visual exam performed by your physician or dentist is enough, since there aren’t any tests for canker sores. However, should the sores be severe or ongoing, your physician or dentist might recommend extra tests11 to check for other potential causes such as:12

Erythema multiforme (a form of hypersensitivity reaction13)

Drug allergies

Herpes infections

Bullous lichen planus (chronic recurrent rashes that happen because of inflammation in the skin and mucous membranes14)


Canker Sore: Introduction

What Is a Canker Sore?

Canker Sore Causes

Canker Sore Types

Canker Sore Symptoms

Canker Sore Treatment

How to Get Rid of Canker Sores

Canker Sore Prevention

Canker Sore Diet

Canker Sore FAQ

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Canker Sore Types

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Canker Sore Treatment

Sources and References

  • 1 WebMD, March 27, 2017
  • 2 MedicineNet, November 7, 2017
  • 3 University Health Service University of Michigan, “Is It a Cold Sore or a Canker Sore?”
  • 4, 6, 10, 11  Mayo Clinic, April 3, 2018
  • 5 York University, “Articulation: The Palates — Hard and Soft”
  • 7, 8, 12 MedlinePlus, April 3, 2017
  • 9 Mayo Clinic, April 3, 2018
  • 13 MedlinePlus, October 24, 2016
  • 14 MedicineNet, December 6, 2017
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