Cold sores are caused by an infection of a herpes simplex virus (HSV). There are different types of HSV, and the one that most often causes cold sores is called HSV-1, although the HSV-2 virus, which usually causes genital herpes, can also cause cold sores if it infects the skin around the mouth. Just the mention of herpes can sound scary and frightening, but herpes infections are common and widespread, with an estimated 67% of the world’s population aged under 50 thought to be infected by HSV-1.
Both of the herpes viruses are highly contagious, and they usually infect people through skin-to-skin contact, such as kissing someone with cold sores. Once the virus is on someone’s skin, it can enter their body through an opening, like their mouth, and once inside it sets up residence in their cells. The virus copies itself and spreads through the infected area, causing the blisters to form on the skin.
Your immune system fights the virus around the outbreaks, and eventually the blisters will clear up, but the virus isn’t eradicated entirely. It gets into the nerve cells in the skin around the infected area and it goes dormant, effectively hiding from the immune system and any treatments. It stays there for life, and it reactivates now and again, causing a fresh outbreak of blisters. Outbreaks can be triggered by:
- Another infection
- Reduced Immune defences
- Changes in hormones