A cold sore is an infection which is caused by an organism called the herpes simplex virus (HSV). This virus is different from the one that causes colds. Although most of the population carry the virus, not everyone gets attacks or cold sores.

The first infection usually occurs during childhood. The virus passes through the skin, travels up a nerve and then hides in a nerve junction until reactivated. When reactivated, the cold sore travels down the nerve to the face where it starts to replicate - causing the tingling sensation. The tingle is your warning that a cold sore is about to appear.

Cold sores can be treated with antiviral treatments containing Aciclovir. When used at the tingle stage cold sore creams can stop the virus multiplication to speed healing and get rid of cold sores.