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Canker sore vs. cold sore: Differences and similarities

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Canker soresCold soresThe role of stress
Canker sores are small ulcers inside the mouth, while cold sores develop on or around the lips. Stress may trigger canker sores, and they are not transmissible. However, cold sores are due to a viral infection, which a person can pass on to someone else.
Medically reviewed by Debra Rose Wilson, Ph.D., MSN, R.N., IBCLC, AHN-BC, CHT
Updated on

Though canker sores and cold sores are common and uncomfortable, they differ in symptoms, causes, and treatment options. 

This article discusses the main similarities and differences between canker sores and cold sores and why it is important to be aware of this information.

What are canker sores?

Young female adult applying cold sore treatment on the lips
Canker sores develop inside the mouth only, while cold sores may appear on your lips or around the mouth. (Justin Case/Getty Images)

Canker sores, also called aphthous ulcers, are small painful lesions that can develop inside your mouth. They typically look like small white or yellow circular sores with a reddish border. If you brush these sores with a toothbrush or your tongue, you may experience a burning or tingling sensation. 

Canker sores are not transmissible. This means a person cannot pass it on to someone else.


The cause of canker sores is not entirely understood, though there are some known triggers and contributing factors:

  • Lesions: If you bite or somehow injure the inner lining of your mouth, a canker sore may develop within hours in that area.
  • Nutritional deficiencies: Being deficient in vitamins and minerals, such as folic acid, iron, or B12, may also induce canker sores. 
  • Hormonal changes: Shifts in your hormone levels, such as during menstrual periods, can raise your risk of getting these ulcers.
  • Smoking: If you smoke, it may make you more likely to get canker sores. 
  • Stress: Emotional and mental stress may induce canker sores.
  • Chronic inflammation: Living with inflammatory conditions, like inflammatory bowel disease, may lead to this type of mouth sore.


Canker sores tend to resolve on their own within a few days or weeks. You may be able to manage them with antiseptic mouth rinses and over-the-counter (OTC) gels to soothe the pain.

Avoiding spicy and acidic foods may also help manage the pain from canker sores.

If your canker sores do not resolve promptly or if you continue developing new ones, consider discussing possible root causes, like nutritional deficiencies, with your health professional.

What are cold sores? 

Cold sores are small fluid-filled blisters on the lips or around the mouth, including the nose, resulting from an infection with the herpes simplex virus.

Though they may start as one blister, cold sores may quickly bubble up to form a cluster on one side of the mouth. You may feel a burning or tingling sensation when these blisters appear. You may also experience fever and fatigue when you have an active infection.

Cold sores are also called fever blisters or herpes labialis. Once you’ve had one, you may be more likely to experience them again.

The herpes virus simplex is highly contagious and can be passed to another person through contact with unhealed cold sores.


Herpes simplex viruses, usually type 1, cause cold sores. You can acquire the virus through personal contact with someone who has it. For example, this could be by engaging in oral sex, kissing, or sharing personal objects.

After an infection, the virus lives dormant on a group of facial nerve cells called a trigeminal ganglion. Specific triggers activate the virus, which then travels along the nerve cells to the lips, causing blisters.

Common triggers of the herpes simplex virus include:

  • fever
  • trauma
  • common colds
  • intense physical activity
  • a compromised immune system
  • UV rays
  • extreme temperatures
  • mental or emotional stress

Avoiding these triggers may help you prevent cold sores if you have one or more per year.


Cold sores tend to resolve without treatment within 2 weeks, but there is no cure for herpes simplex viruses.

The virus stays in your body after cold sores heal. It may become active again during times of physical or mental stress.

Not everyone with the virus experiences cold sores, even under the same stressful circumstances.

Topical and oral treatments may speed up healing and resolve blisters within days. These may include:

Cold sores are transmissible until the blisters heal completely. During the healing process, blisters typically turn into scabs, which fall off when they dry up.

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Stress and mouth sores

Emotional or physical stress may trigger cold sores.

Though canker sores are slightly more difficult to track, 2015 research also shows a correlation between cortisol, anxiety, and recurring symptoms. 

Stress management may be key in managing and preventing both cold sores and canker sores. 

The Anxiety and Depression Association of America recommends frequent physical activity as a stress-management technique. 

Other strategies to manage stress levels may include:


Cold sores are transmissible blisters around the mouth that develop due to the herpes simplex virus. Canker sores are ulcers that occur inside the mouth, which you cannot pass on to other people. Injury, stress, or nutritional deficiencies may lead to canker sores.

Both cold sores and canker sores resolve on their own without treatment. It is possible to manage symptoms, which may help you find relief from pain and tingling.

Download the free Optum Perks Discount Card to save up to 80% on some prescription medications.

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