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Skin Problems

Cold Sores

Prevention - Home Treatment - When to Call a Health Professional

Cold sores (fever blisters) are small, red blisters that usually appear on the lip and outer edge of the mouth. They often weep a clear fluid and scab over after a few days. They are sometimes confused with impetigo (See Impetigo), which usually develops between the nose and upper lip. The fluid that weeps from impetigo is cloudy and honey-coloured, not clear.

Cold sores are caused by a herpes virus. Herpes viruses (chickenpox is another kind) stay in the body after the first infection. Later, something triggers the virus to become active again. Cold sores may appear after colds, fevers, exposure to the sun, stressful times, or during menstruation. Sometimes they develop for no apparent reason.


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  • Avoid kissing a person who has a cold sore. Also avoid direct skin contact with genital herpes sores See Genital herpes is caused by the herpes simplex virus, which also causes cold sores. Genital herpes is easily spread through sexual contact and any other direct contact with genital herpes sores. and herpes sores elsewhere on the body.

  • Use sunscreen on your lips and wear a hat if exposure to the sun seems to trigger cold sores.

  • Reducing stress may help in some cases. Practise relaxation exercises often. See Relaxation Skills.

Home Treatment

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  • At the first sign of a cold sore (tingling or prickling at the site where the sore will appear), apply ice to the area. This may help reduce the severity of the sore.

  • Apply petroleum jelly to ease cracking and dryness.

  • Apply a paste made of cornstarch and a little water to the sore.

  • Products such as Blistex may ease the pain. If you apply these products by touching the container to your lips, don't let anyone else use the container.

  • Be patient. Cold sores usually go away in 7 to 10 days.

When to Call a Health Professional

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Call if sores last longer than 2 weeks or you have frequent outbreaks of cold sores. A prescription medication may reduce the frequency and severity of outbreaks.


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