Mouth Irritations: Cold Sores and Canker Sores

Most of us tend to think of cold sores as a cold weather ailment, but did you know that the sun can sometimes trigger them? Cold sores and canker sores are the two most frequent irritations in our mouths. Let’s take a look at each of them.


Cold sores are also called fever blisters. You will usually find these outside your mouth on your lips, chin or cheek, though they can occur inside your mouth too. They usually start as a blister which then breaks and scabs over.  Cold sores are caused by a virus and can be contagious, especially during when blisters are present.  Though the blisters disappear, the virus stays in your body—this is why they come back.


Stress, fever, illness, injuring the area and exposure to sunlight are all triggers for a cold sore outbreak. You may feel itching, tingling or burning in an affected area one to three days before the blister appears. Sometimes applying a prescription medication at this time, before the blisters appear, will shorten the duration of your outbreak. Using a lip balm or lipstick with an SPF of at least 15 may help decrease sun exposure related outbreaks.


Though there currently is no cure, some dental laser studies have encouraging results showing that cold sore areas treated with the laser do not come back in that same area.


Other things you can do during an outbreak are:

  • Keep the area clean and dry to prevent bacterial infection
  • Avoid foods that irritate the sores
  • Avoid kissing others or touching someone else after touching your sores
  • Applying sunscreen or lip balm with SPF 15 (You may want to use a Q-tip to apply so as not to contaminate the whole tube.)


In contrast, canker sores occur only inside your mouth with your tongue, roof of your mouth, floor of the mouth, throat and the insides of your cheeks or lips as the most common locations. They are painful oval-like ulcers with a yellow-white center surrounded by a red ring and are usually larger in size but slower to heal than a cold sore. Though you cannot spread them to others, they do tend to come back in your own mouth.


The cause of canker sores is not well understood. One school of thought says they come from a fault in our body’s immune system. A second believes nutritional deficiencies are at fault, and a third blames our body’s hormones. We do know that emotional stress and mouth injuries can trigger canker sore formation.  You can expect the pain to last three to four days with complete healing taking 7 to 10 days. There is no cure but there are products that can make the symptoms tolerable.  If those are not working well for you, some dental lasers can create a “band-aid” over the canker sore. Some studies have even indicated a faster healing rate after laser treatment of canker sores and other ulcers.

Other things you can do include:

  • Rinsing with a peroxide-containing mouthwash to keep the area clean
  • Avoid spicy or abrasive foods that can irritate the lesion
  • Continue your oral home care (brushing and flossing)
  • If you have frequent outbreaks, ask about being tested for nutritional deficiencies or allergies


Though these two sores are the ones most commonly seen, they are by no means the only causes of irritation in your mouth. Many mouth sores, including the start of oral cancers, look the same to an untrained eye, so consult your dentist on any mouth sore or irritation that lasts more than two weeks to be sure it isn’t something more serious. If you would like to explore whether dental laser treatment would help your cold sores or canker sores, I invite you to call my office at 440-960-1940.

NOTE: The information in this article is not meant to replace the clinical judgement of your healthcare professionals.