Cold sores (fever blisters) - What are they? / What causes them? / The herpes virus.
What is a cold sore?
A cold sore is a type of facial lesion that either forms on a person's lips or else on the skin in the area immediately adjacent to their mouth. (Pictures / Diagram)
Is there a difference between cold sores and fever blisters?
What causes cold sores?
While there are a number of risk factors and triggers for 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.
- 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.
How the cold sores/herpes virus relationship works.
The way the herpes simplex virus causes cold sores is not as straightforward as you might think. Here are the details.
Cold sores are not a sign of a recently acquired herpes simplex infection but instead a reactivation of virus particles already living in your body. Cold sores occur when herpes virions, which have been lying dormant ("asleep"), become reactivated.
Cold sores are actually caused by herpes virus particles that already (previously) infected your body.
Where do these dormant virus particles come from?
The dormant virions come from a previous 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 this initial exposure to the recurrent lip and face sores that they experience later on.
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.