Cold sores (fever blisters): What are they?
What causes them?

What are cold sores?

Cold sores are a type of facial lesion that form either on a person's lips or else on the skin in the area immediately adjacent to their mouth. They can be managed using a number of different prescription, non-prescription (OTC) and home-remedy treatments and medications, however, there is no true "cure" for cold sores.

Is there a difference between cold sores and fever blisters?

No, cold sores and fever blisters are the same thing. These lesions are also referred to as "recurrent herpes labialis."

What causes cold sores?

While there are a number of factors that can trigger cold sore outbreaks, their underlying cause is the herpes simplex virus. However, in most cases, not the type of "herpes" that you're probably thinking of right now. There are actually two types of herpes virus. They are referred to as "type 1" and "type 2." Here's the difference between them.

Herpes simplex virus - Type 1.

Herpes simplex virus type 1 ("HSV1") generally only infects those body tissues that lie "above the waistline" and it is HSV1 that causes cold sores in the majority of cases.

Herpes simplex virus - Type 2.

Herpes simplex virus type 2 ("HSV2") usually only infects those body tissues that lie "below the waistline." It is this virus that is also known as "genital herpes." Herpes simplex virus type 2 is not usually the virus that causes a person's cold sores, although it can.

The cold sores/herpes virus relationship is really pretty involved.

The way the herpes simplex virus causes cold sores is not as straightforward as you might think. Here are the details.

Cold sores are actually caused by herpes virus particles that already (previously) infected your body.

When you think of having an infection you usually assume that you were recently exposed to the germ that has caused your problem. With cold sores that is not the case.

Cold sores are not a sign of a recently acquired herpes simplex infection but instead a reactivation of herpes virus particles already living in your body. Cold sores occur when latent herpes simplex virus particles, which have been lying dormant ("asleep"), become reactivated.

Where does this dormant herpes simplex virus come from?

The dormant virus particles come from a previous herpes infection. A person's initial herpes simplex virus infection, termed "primary herpetic stomatitis," does not usually take the form of a cold sore and therefore a person may not relate their initial exposure to the herpes virus to the recurrent cold sores that they get.

What are the signs and symptoms of a person's initial herpes (HSV1) infection?

The signs and symptoms associated with a person's initial infection of the herpes simplex virus (termed "primary herpetic stomatitis") usually take the following form:

• The first signs of the infection are characterized by nonspecific constitutional symptoms. These can include: fever, irritability, headache, and pain upon swallowing.
• A day or so after the infection's initial signs have appeared the person's mouth becomes painful and their gums become intensely inflamed.
• Usually by day three of the infection a number of tiny blisters have formed throughout the person's mouth.
• These blisters soon rupture resulting in gray colored ulcers.
• These ulcers can be very painful and often interfere with a person's ability to eat.
• The ulcers will eventually heal. Usually the entire infection has run its course within 10 to 14 days.

Why don't the symptoms of primary herpetic stomatitis seem familiar to you?

If you don't remember having had the classic signs and symptoms of primary herpetic stomatitis it might be because you experienced them as a small child. Most cases occur before the age of 7.

In other cases, if you don't remember having all the classic signs and symptoms, it's probably because your case was subclinical. This is by far the most common occurrence.

It has been estimated that 99% of all cases of primary herpetic stomatitis are subclinical, meaning that the course the infection ran was so slight that its symptoms were not apparent. It is quite possible that when you had the infection that, at most, you only experienced one or two low-grade mouth sores.