What is the difference between cold sores and canker sores

A little irritation develops near or inside your mouth, and you start to wonder what’s wrong. It hurts a lot more than it should, considering the small size. It seems to last a while, and you can’t figure out whether it’s a cold sore or canker sore.

So, what exactly is the difference between a cold sore and a canker sore?

Cold Sore vs. Canker Sore

The location of the sore often can help you identify if it’s a canker sore or a cold sore. Cold sores usually appear around the lips and the outside of the mouth, whereas canker sores only occur within the mouth.

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What Is a Cold Sore?

Outside the mouth is where you’ll find a cold sore, sometimes called a fever blister. It usually appears as one or several red, blistered areas on your lips. The blisters often will break open causing an open sore, or ulcer.

Within a few days, a scab will form. Some areas of the mouth take longer to heal because they frequently stretch when you talk, eat, or yawn.

Symptoms depend on whether you have a new infection of herpes simplex virus (HSV), which causes the sores, or if you’ve had the virus for a while. If you have a new infection, your symptoms may include:

  • Burning or tingling and the development of sores on and around the lips and mouth.
  • Sore throat or pain when swallowing.
  • Swollen lymph nodes.

If you have had HSV for a while, you may experience cold sores periodically, often in the same spot. Early symptoms may include burning, itching, or stinging around the mouth prior to the sores forming; however, the symptoms tend to be less severe after the first outbreak.

What Causes Cold Sores?

The virus that causes cold sores is HSV and, unfortunately, the sores are contagious when they’re open. The virus can be spread through the following:

  • Sharing utensils, drinks, towels.
  • Close person-to-person contact, such as kissing.
  • Using someone else’s lip balm or lipstick.

The herpes virus stays in your body forever and can cause cold sore outbreaks at any time. Often, they’re triggered by things such as extreme temperatures, exhaustion, stress, or a weakened immune system.

When you feel a cold sore coming on, usually indicated by a tingling or itching on the affected area, consider anything out of the ordinary that you’ve been experiencing, as this could be your trigger. Once you figure out what your triggers are, you can try to avoid them. Use sunblock if a cold sore is caused by sun exposure or take a few minutes to relax if stress is a trigger for you.

How to Treat a Cold Sore

While there’s no cure for cold sores, treatment can help to shorten the lifespan or weaken the severity. Some people start treatment when they first notice symptoms. A cold sore treatment van provide symptom relief, and can include:

  • Antiviral topical ointment.
  • Oral antiviral medication.
  • Over-the-counter topical anesthetic or anti-inflammation agents.

Your first cold sore can take up to three weeks to heal, but later ones may disappear in a week or two. While there’s not usually a reason to go to the doctor for a cold sore, your doctor can test for the virus with a swab and culture and prescribe antiviral medication.

Cold sores can form inside the mouth for children under 5. These can easily be mistaken for canker sores; however, canker sores can only form along the mucus membrane. First-time cold sore may include symptoms of sore throat, muscle aches, swollen lymph nodes, painful gums, and fever.

What Are Canker Sores?

Canker sores are found on the inside of the mouth, including the lips, cheeks, and tongue. They’re small ulcers that usually have a red base and may be covered by a white or yellow layer. Canker sores have three variants: minor, major, and herpetiform. Common symptoms include:

  • Bleeding gums.
  • Painful gums.
  • A painful lump on the gums.

In the case of a herpetiform canker sore, the sores themselves will be very small, almost pinpoint. However, they occur in clusters and can merge to form a larger canker sore. Herpetiform canker sores will also have irregular edges but should heal without scarring in about two weeks.

What Causes Canker Sores?

Canker sores can be caused by things such as:

  • Food allergies.
  • A weakened immune system.
  • Mouth injury (like biting your tongue or cheek).
  • Some medicines.
  • Viruses/bacteria.
  • Irritation from orthodontic braces.

How to Treat Canker Sores

Canker sores aren’t contagious, and they are not easily visible to others. They can be painful, though.

  • Try an oral pain reliever since ointments are difficult to keep in place when the sore is inside your mouth.
  • Keep your mouth clean by brushing regularly.
  • Use an anesthetic mouth rinse to ease pain.
  • Avoid spicy, acidic, or salty foods during healing, which can take up to two weeks.

There’s no reason to go to the doctor unless the sores return frequently, last more than two weeks. or are particularly large.

The Main Difference

So, what is the difference between a canker sore versus cold sore? Location, location, location!

  • Cold sores are usually on the edge of the lips and very rarely on the inside of the lips, while canker sores are always inside the mouth.
  • Cold sores are contagious and can be treated with antiviral ointments and pain relievers, while canker sores require only pain relief.
  • And both can last a few weeks.

For more information on treating oral sores or to find a doctor, contact UPMC.


Editor's Note: This article was originally published on , and was last reviewed on .

About UPMC

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