Cold Sores vs. Canker Sores: How to Spot the Difference

Cold sores and canker sores are common, non-harmful blisters that occur in and around the mouth. While they share some similarities, they are ultimately two different ailments. In this article, you will learn about their differences and how to spot them.

Let’s start!

Canker sore

Also known as aphthous ulcer, canker sore occurs exclusively inside the mouth. They can be found in the gums, on or below the tongue, inside the cheeks or lips, or on the soft palate.

Canker sores are round or oval-shaped, and they occur in different sizes ranging from small to large.

Some symptoms of canker sores are:

    • fatigue
    • fever
    • eye discomfort
    • abdominal pain
    • swollen lymph nodes
    • round white or yellow sores or rashes with a red border
  • burning or tingling sensations in your mouth

Cold sore

Also known as fever blisters, cold sores are caused by Herpes Simplex Virus (or HSV). They usually occur on the mouth or around it, like the lips, face, and cheeks, among others.

Some symptoms of cold sores are:

  • fever
  • headache
  • fatigue
  • nausea
  • body pains and aches
  • swollen lymph nodes
  • sore throat or pain when swallowing
  • burning or tingling in the areas where cold sores develop

If you’ve had a cold sore for a while, you may experience the following symptoms:

  • burning, itching, or stinging sensations in the area of the cold sore
  • an outbreak of cold sores which are often fluid-filled and painful
  • crusting over of the sores when they break open and form scabs
  • healing of the sores in one to two weeks, usually without a scar

Differences between cold sores and canker sores

Below is a short guide that will help you to spot the differences between canker and cold sores.


Canker sores appear only inside the mouth. They are found in soft tissues like the cheeks, gums, on the tongue, under the tongue, etc. They typically appear in small white or yellow circles with a red border.

On the other hand, cold sores appear outside the mouth and around the lips. They may also appear inside the mouth and around the face. Furthermore, they appear like a cluster of blisters.


Cold sores are directly caused by Herpes Simplex Virus (HSV-1). However, the exact cause of canker sores is unknown, although experts believe they may be caused by mouth trauma, bacteria or viruses, and immune issues.


Both canker sores and cold sores heal on their own. It takes the former between one and two weeks to heal, while the latter may require up to four weeks. Additionally, cold sores do not leave scars after healing, while canker sores sometimes cause scarring.


While cold sores can be transmitted to other people through physical contact, canker sores are not contagious. The easiest way to differentiate between cold sores and canker sores is through their location and appearance.

If the sore is in your mouth and appears as a white or yellow ring with a red border, it is likely a canker sore. However, if it occurs outside your mouth and appears as a cluster of blisters, then it is likely a cold sore. Regardless, we advise that you consult your doctor or dentist to determine the exact nature of the sore and get a proper treatment plan.

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