Cold sore (herpes simplex)

General information

Cold sores are a common infection caused by the herpes simplex virus, and they usually appear around the area of the mouth, lips or face. The virus is contagious through contact or droplets, and the majority of people are carriers of the virus.

The primary infection usually shows no symptoms. Many different reasons can trigger cold sores. The recurrence of cold sores is very common.

The first symptoms are a burning, itching or tingling sensation and redness in the area of skin or mucous membrane. After this, small blisters appear, sometimes quite quickly, sometimes the next day. Once the blisters burst, they form painful ulcers, which crust over into a scab in a couple of days.

The amount of virus is the highest, and cold sores are the most contagious, when the blisters and scabs are visible.


The blisters and ulcers clear up of their own accord without treatment in 1 to 4 weeks, and if the symptoms are mild, no treatment is necessary. You can try medications that are available at pharmacies without a prescription to reduce your symptoms. The pharmacy staff will help you choose the right product.

When should you seek medical advice?

You should seek medical advice if

  • your symptoms are severe and widespread
  • the infection spreads to or near your eyes
  • you show symptoms of facial paralysis
  • you have an illness or medication that affects your body’s immune system.

If you have frequently recurring cold sores, you may want to consult a doctor to assess whether you might benefit from an antiviral medication.

This Self-care instruction has been produced in collaboration with Duodecim Terveyskirjasto

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Updated  5.6.2020