Cold Sores
A Patient's Guide to Cold Sores
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Why do I have cold sores?

Cold sores are caused by a virus. Once you have been exposed to the virus and infected with the herpes virus you are infected for life. Exposure to the HSV-1 virus and infection commonly occurs in childhood.

It is quite common for a child to become infected from a parent or a sibling. In developing countries about 1/3 of children have been infected by the age of 5 years whereas in the developed western world infection is slightly lower at about 20%.
By the age of 14 more than 70% of children are infected with the HSV-1 virus.

Infection usually occurs when the virus enters through small breaks in the skin possibly at the site of injury or trauma or just small cracks in the skin. The virus then travels along the nerves to reside next to the spine in a location called the dorsal root ganglion.

For various reasons the virus which is normally 'contained' in this location starts to multiply and then travels down the sensory nerves to the skin.
Once in the cells of the skin the virus multiplies, damaging the skin cells causing the blisters that we call a cold sore to develop. This virus infection of the cells (whether a cold sore is visible or not) is always looking for new cells to infect, this process is called viral shedding.

At this time there are large numbers of herpes particles being shed or released and as a result it is easy to expose or even infect others with the virus.

This is the time when hygiene is extremely important.

Are cold sores common?

About 20-40% of the population will experience cold sores.

The frequency of recurrence is very variable ranging from monthly to a few a year to every few years.


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