Cold sores

What causes cold sores?

Cold sores are caused by the herpes simplex virus, and usually the herpes simplex virus type 1 (HSV-1). About 90% of people will be infected by HSV-1 at some point in their lives. The first infection may not even be noticed or it may cause a flu-like illness and painful ulcers in the mouth.

Following the first attack, the virus will lie dormant in nerve cells, but, in some people, it is triggered and reactivates. The reasons for this reactivation are not fully understood, but may include:

  • Another viral infection, such as a cold or influenza.
  • Fever.
  • Physical or mental stress or exhaustion.
  • Over exposure to wind or sunlight.
  • Menstruation (in women).
  • Underlying immune system problem (which means the sufferer cannot fight off the infection) or as a side-effect of immunosuppressant drugs (used to treat cancer or transplant patients).

How are cold sores spread to others?

They can be spread by contact such as kissing but also by sharing toothbrushes, towels, cutlery, etc.

What happens during an outbreak?

  • Tingling or itchiness around the lips usually precede an outbreak.
  • Small blisters appear and enlarge until they burst, leaving open sores.
  • These open sores crust over.

Most cold sores heal in about one week

How are cold sores treated?

In most cases, cold sores are an irritating nuisance which clear up within a few days. However, over-the-counter treatments are available for more troublesome outbreaks and are most effective if applied as soon as you feel tingling or itching develop. You should only consult your doctor if the cold sore is accompanied by fever, red or sore eyes, or if the area is very inflamed and you notice a yellow-coloured discharge.

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