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Cold sore on the outside of a mouth.

Cold sore on the outside of a mouth.
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Cold sores

2-minute read

Cold sores are small blister-like spots that appear in or around the outside of the mouth. Cold sores are caused by a virus, known as herpes simplex (HSV). About 80 per cent of adults are infected with the virus. Most people are infected when they are young and the infection lasts for life. However the virus can remain dormant (inactive) in many people, meaning that cold sores may never appear.

However, there are various factors that can cause the virus to become active resulting in one or more cold sores. They can include:

  • tiredness and fatigue
  • a break in the skin near the affected area
  • periods (menstruation)
  • emotional upsets or stress
  • strong sunlight, cold or wind
  • alcohol
  • colds, flu or fevers that make the body less able to fight off infection

Cold sores start with an itchy and tingling sensation usually on the mouth, lips or nose (and can form on the genitals) and may form small blisters which crust after 3 days.

Cold sores usually clear up after two weeks without leaving any scars. However, they can be highly contagious, even when the blisters aren’t present. The virus can spread between people by direct physical contact, such as kissing, skin to skin contact, sharing drink containers or eating utensils, towels or toothbrushes with someone who already has a cold sore.

As well as a blister-like spot, the following symptoms are also common:

Your pharmacist may recommend products to treat the short term symptoms of a cold sore.

Not sure what to do next?

If you are still concerned about your cold sores, why not use healthdirect’s online Symptom Checker to get advice on when to seek medical attention.

The Symptom Checker guides you to the next appropriate healthcare steps, whether it’s self care, talking to a health professional, going to a hospital or calling triple zero (000).

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: August 2018

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