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What are the main differences between a canker sore vs cold sore?

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    Understanding the difference between canker sores vs cold sores in the mouth is helpful, as both conditions are different and they are typically caused by different things.

    In this article, we explain what cold sores and canker sores are, what causes them, how they are different, and how to treat them.

    Please note that if you are concerned with a sore in or on your mouth, you should contact a medical professional for the best course of treatment.

    Fever blister vs cold sore vs canker sore - what's the difference?

    Fever blisters, more commonly known as cold sores, form on the outside of the mouth. They are usually painful and appear in the corners of the mouth or on the lips and are caused by the existence of the herpes simplex virus.

    Cold sores are very contagious and can spread easily from person to person, so it's important to identify them and take preventive steps to ensure that you don't pass them onto people in your family.

    Canker sores (aphthous ulcers), on the other hand, only form inside the mouth. They are usually white or yellow in appearance, surrounded by a red border. They can appear on your tongue, on your cheeks, or even towards the back of your throat.

    Unlike cold sores, canker sores are not contagious. They can also be caused by numerous factors, including stress, sleep deprivation, and some infections. That being said, they are often painful and cause discomfort, particularly large sores that form on your tongue or on the inside of your lips.

    You can use our comparison table to find out more about the differences between cold sores and canker sores, to help you determine which you might have:

    Cold Sore (Fever Blister) 

    Canker Sore (Aphthous Ulcer)


    On the lips or the corner of the mouth 

    Inside the mouth (on the tongue, underside of the lips) 


    Fluid filled sores on the outside of the mouth 

    Yellow or white spots on the inside of the mouth with a red border 







    Common Cause 

    Infection (herpes simplex virus)

    Stress, sleep deprivation, infections 

    What causes cold sores and canker sores?

    Cold sores are caused by the presence of the herpes simplex virus. This is an extremely common virus, which is thought to affect up to 9 in 10 people in the United States alone from time to time.

    Some people don't show any signs of infection of the virus, while others can feel under the weather for a while and may see cold sores break out on their mouth and lips. Cold sores can go away on their own, but they usually need to be treated with a prescription.

    In contrast, canker sores have numerous potential causes and it's not as easy to diagnose what causes them. For instance, some people who are stressed and overly tired might develop canker sores, while they might also be triggered as a result of a Vitamin B12 deficiency or by excessive smoking.

    Given that different things can cause each type of sore, it begs the question - how can they be treated? Let's investigate.

    Cold sores vs canker sores treatment options

    If you notice a cold sore on your mouth or lips, it's important to note that it is contagious. So, avoid kissing family members and try not to touch it with your hands, as you risk spreading it to others. You should also avoid sharing cups and bottles while the infection is present.

    As for treatment, the best way to treat a fever blister is to visit your doctor's office. Your doctor may prescribe an antiviral medication in the form of a topical cream or in tablet form. This will usually cause the sore to reduce in size and disappear in a few days.

    However, if the sore remains for more than a week, it could be a sign of a more serious condition and you may need to return to see the doctor for a different course of treatment.

    Canker sores often go away on their own and they don't necessarily need any treatment. However, they cause discomfort and may impact your ability to eat and drink, and may even keep you up at night.

    In this case, you can go to the pharmacist to request an over-the-counter cream or gel to apply to the canker sore, which will help to numb the pain. You might also be advised to use an antiseptic medication to prevent the canker sore from spreading or from becoming worse.

    If you experience regular canker sores, some lifestyle changes may be required, including:

    • Canker sores can be caused by excessive smoking and vaping, so stopping smoking is an obvious step to take.

    • If your canker sores are caused by stress or fatigue, removing or reducing the stressor is a good step to take.

    • Some people who follow vegan diets and are B12 deficient are more likely to develop canker sores. So, taking a B12 supplement can be a simple and easy solution.

    The verdict - cold sores vs canker sores

    Both cold sores and canker sores can be painful, but they are caused by different things. Cold sores are a sign of a specific viral infection, while canker sores may be caused by stress, fatigue, or a Vitamin B12 deficiency.

    Make sure you identify which type of sore you have, using the table above, and start on the best course of treatment to return to normal as soon as possible.

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