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Cold Sore vs. Canker Sore

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Canker sores, or mouth ulcers, and cold sores are both types of mouth sores – and both can be painful and aggravating to deal with. Yet the two are very different. If you have a mouth sore it’s important to know which one you are suffering from so you can treat it successfully and recover faster.

There are several ways to tell the difference between a cold sore and a canker sore. Knowing what to look for means you can be sure of which one you have.

What Is a Canker Sore or Mouth Ulcer?

A canker sore – also known as an aphthous ulcer – is a type of mouth sore that forms on the soft tissues in your mouth, such as on or under your tongue and inside your cheeks or lips.1Canker sores are also commonly referred to as mouth ulcers.2 There’s no difference between a canker sore and a mouth ulcer besides their name.2

Cankers are typically shallow, round or oval ulcers that vary in size. They may appear whitish or yellowish with a red border.2 Canker sores tend to be painful, making it difficult to eat and talk, and large ones can take a while to heal.3

Mouth ulcers are typically caused by trauma, such as aggressive tooth brushing, eating sharp-edged foods such as potato chips, or orthodontic braces and wires that rub against the inner cheek. Other triggers for canker sores include stress, diseases of the immune system and vitamin deficiencies. Mouth ulcers are not contagious.

What Is a Cold Sore?

Cold sores are small, fluid-filled blisters that usually form along the borders of the lips, and sometimes on the face. They are caused by certain strains of the herpes simplex virus (usually HSV-1), and many people experience a burning, itching or tingling sensation before the actual sore appears.4

Cold sores can take up to seven to 10 days to heal completely6, but you may be able to get rid of your cold sore in as few as 2½ days* with an antiviral topical cream such as Abreva® Cream, which is available over the counter. Compare Abreva® Cream to other cold sore treatments.

*Median healing time 4.1 days. 25% of users healed within 2½ days when used at first sign.

Cold Sore vs. Canker Sore (Mouth Ulcer)

While these two types of mouth sore are often confused, they differ in several ways.

Cold Sore and Mouth Ulcer Causes

A key difference between cold sores and cankers is that cold sores are contagious as they are caused by a virus, whereas canker sores are not. Various triggers can lead to the reactivation of the virus that results in an outbreak of cold sores. Triggers vary from person to person but include stress, fatigue, sunlight exposure, hormone fluctuations and illnesses such as colds and flu. You can’t develop a cold sore unless you have been infected with the virus first.

Canker sores can be caused by a number of factors, such as stress, nutrient deficiency and injury to the inside of the mouth.

Where Are Cold Sores and Canker Sores Located?

Canker sores are found only inside the mouth – on the inner cheek, lips or tongue – whereas cold sores are experienced on the lip area, from the outer to the inner edges, but rarely inside the mouth.

Appearance of Cold Sores and Mouth Ulcers

A canker sore or mouth ulcer may appear like a whitish lesion or patch, with an inflamed reddish edge. It is always found within the soft moist tissues of your mouth. A cold sore appears as a blister or cluster of blisters around your lip area: on the corners, outer edges or on the lip itself.

How Canker Sores and Cold Sores Spread

A canker sore can’t be spread from person to person or within your mouth. While you may experience one or more canker sores at one time, it’s likely they have been triggered by the same thing. The herpes simplex virus, which causes cold sores, is highly contagious. It is easily transmitted to others by touching, kissing, through oral sex or by sharing items such as glasses, forks, lipsticks and lip balm.

Stages of a Cold Sore or Mouth Ulcer

Although a canker sore may develop gradually, you will likely notice it all of a sudden as it starts to hurt when you touch it with your tongue, toothbrush or with food. Most mouth ulcers will heal without scarring within 1 to 2 weeks.1

A cold sore may be felt before it’s visible. You may experience a tingling, burning or itching sensation in the area where a cold sore blister then appears. The blister is usually red with an uneven and inflamed surface. Once the blister has formed, it often crusts over, weeps liquid and then eventually heals. Cold sores may take up to two weeks to heal completely.6 Using a specially formulated cold sore cream such as Abreva® Cream early on in this process can reduce the healing process to just a few days.*

*Median healing time 4.1 days. 25% of users healed within 2½ days when used at first sign.

Treating Canker Sores and Cold Sores

While there are many differences between canker sores (mouth ulcers) and cold sores, they are both painful and irritating to experience. Cold sores, however, can also make you feel uncomfortable or unhappy about your appearance. Using a cream such as Abreva® Cream as soon as you feel a cold sore coming on will speed your recovery, helping your lips to look healthy again sooner.


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1. Canker sore. Mayo Clinic. Accessed 11/13/19.

2. 2. Canker sores (mouth ulcers). Accessed 3/23/22.

3. A Detailed Guide to Canker Sores: Causes, Prevention, Remedies, Treatment, and More. Everyday Health. Accessed 11/13/19.

4. Canker Sores. PeaceHealth. Accessed 11/13/19.

5. Cold sore. Mayo Clinic. Accessed 11/13/19.

6. What’s the Difference Between Canker Sores and Cold Sores? Healthline. Accessed 11/13/19.

7. Cold sore. NHS Inform. Accessed 10/12/19.