When you see an ugly sore in or around your mouth, you probably find yourself asking questions like what is it? Is it contagious? How soon will it go away? Is it really caused by herpes?

Chances are it’s one of two types of oral infections. If it’s on the outside of your mouth, it’s a cold sore, also known as a fever blister. If it’s inside your mouth, it’s a canker sore. Whichever it is, you can assume the sore will disappear within a couple of weeks.

Let’s clear up those old rumours. Cold sores are caused by a form of the herpes virus, but it’s not the same virus that causes the venereal disease. Nonetheless, once you’re infected with the cold-sore-causing herpes virus, you’re infected for life. That means that an episode of stress, fever, illness, injury or overexposure to the sun can trigger a bout of cold sores. Usually, you’ll experience itching, tingling or burning in the lip area one to three days before the fever blister occurs.

You’ll experience the same sorts of sensations when a canker sore is about to erupt. These ulcer-like sores found on the inside of the mouth aren’t associated with any particular virus or bacteria. In fact, no one knows what causes canker sores. They have been linked to some food allergies and mouth trauma, but there is no irrefutable evidence.

Now let’s get on to what you really want to know: how do you make them go away? Unfortunately, you can’t. But there are some dos and don’ts:

• Don’t kiss anyone while plagued by cold sores. They are very contagious. However, canker sores are not infectious, so feel free to show your affection.
• Don’t touch your cold sores.
• Do keep cold sores clean and dry. If they cause you a lot of pain, try using a pain-relieving cream.
• Do use an analgesic cream to help numb painful canker sores.
• Do eat a bland diet when afflicted by either kind of sore.
• Do see your dentist for prescription medications if the pain becomes unbearable, or if episodes become chronic.

While there’s no cure for either of these ugly sores, there’s at least some small comfort in knowing that in an average of two weeks, they’ll be out of your life.