Do I Have a Cold Sore or Canker Sore?

Reviewed on 9/24/2020

Do I have a cold sore or canker sore?

Cold sores and canker sores are painful and difficult to differentiate.
Cold sores and canker sores are painful and difficult to differentiate.

Having a cold sore or canker sore is painful and differentiating them isn’t always easy. However, a cold sore isn’t the same as a canker sore. The simplest way to differentiate between cold sores and canker sores is by location. Cold sores are usually on the outside of the mouth, typically directly on the lips, whereas canker sores are always on the inside of the mouth.

  • Cold sores/fever blisters: These are caused by  a type of infection and they are very contagious and quite painful. They usually start as tiny blisters clustered together that break and create a sore. The early blisters are red and full of fluid. Eventually, these have a crusted appearance. Cold sores develop on the outside of the lips but may also appear on the gums, tongue and/or on the roof of the mouth.
  • Canker sores: These are a type of mouth ulcer and may be relatively small. They have a red border and a white or yellow center. These are usually found on soft parts of the mouth such as the inner cheeks, inner lips or at the base of your gums.

What should I know about cold sores?

Cold sores are usually caused by the herpes virus and it is highly contagious.

Symptoms of cold sores include

Lesions are commonly preceded by an itching, burning or tingling sensation. The lesions are often painful and can come back on a regular basis. They might be triggered by exposure to sunlight, local injury, allergies, stress, hormonal changes or an illness such as a bout of fever or flu. The infection usually heals within 7 to 10 days.

Treatment of cold sores 

There is no cure available for the herpes virus; however, symptoms may be treated

What should I know about canker sores?

Canker sores are mouth ulcers that are not contagious. They are autoimmune in nature. Some may be due to repeated trauma to the lining of the mouth. For example, biting the inside of our own cheek could wind up as a canker sore because the body tries to heal the wound. You  may be likely to bite the same spot inside your mouth several times making the canker sore more severe.

Symptoms of canker sores include

  • Severe pain in the mouth and one or more sores on the mouth.
  • Sores are usually small and rarely become large. They bleed easily, usually while brushing the teeth.
  • They usually last for 14 to 18 days.
  • They are usually associated with physical or emotional stress, become painful and commonly come back in multiple areas.
  • They are triggered due to vitamin deficiency, injury, infection, spicy foods, poor diet, hormone fluctuations and even allergies
  • Very rarely, canker sores are caused by a viral infection that includes fever as a symptom.

Treatment of canker sores 

Canker sores are not easy to treat

  • They usually heal with over-the-counter pain medication or a numbing topical gel to treat the pain (benzocaine or hydrogen peroxide). Sometimes, doctors may even prescribe oral steroids to treat canker sores.
  • Gargling with warm salt water or a solution of baking soda and water can shorten healing time and reduce pain as well.
  • Using ice or honey may also numb the pain.
  • Canker sores usually go away within 10 days, but if they last more than 14 days immediate medical attention may be required.
  • Staying away from highly acidic or spicy foods and eating a diet rich in vitamins and nutrients may prevent recurrence.
  • Sometimes, a toothpaste with sodium lauryl sulfate may trigger canker sores; trying a toothpaste without sodium lauryl sulfate may prevent recurrence.


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