What are the causes of Cold Sores and Fever Blisters?

By  ,  Onlymyhealth editorial team
Jan 18, 2013
Quick Bites

  • Cold sores and fever blisters are group of tiny blisters on the lip.
  • During cold sores, the skin often turns red, swollen and sore.
  • Cold sores and fever blisters are caused by herpes simplex virus 1.
  • Cold sores are contagious and can spread with close contact.

Cold sores and fever blisters are group of tiny blisters on the lip and around the mouth. The skin often turns red, swollen and sore and when the blisters break, a crust is formed over the resulting sore. However, they often heal within two weeks. The cold sores can spread from one person to another by close personal contact such as kissing or by oral sex.

cold sores

The cold sores are caused by the herpes simplex virus which is closely related to the genital herpes.  Both the herpes simplex viruses not only affect the mouth but can also affect the genitals.


Most of the people who are infected with the virus that leads to cold sores never develops any symptoms. But they can they spread the infection to others. Common signs and symptoms of cold sores include:

Itching and Tingling:

people infected the virus may feel an itching, burning or tingling sensation around the lips for a day or more before the eruption of the blisters.


Tiny fluid filled blisters develop on the skin around the lips which break down along the border where the edge of the lips meets the skin of the face. The blisters can also develop around the nose or cheeks as well.

Oozing and Crusting:

The tiny blisters may merge and burst making the shallow open sores to ooze the fluid out and crust over.

Apart from these symptoms, people are having the first time outbreak may also experience fever, sore throat, headache, muscle aches and swollen lymph nodes.

fever blisters

Causes of Cold Sores and Fever Blisters

Cold sores and fever blisters are caused by herpes simplex virus 1 while the herpes simplex virus 2 is responsible for causing genital herpes. But the type of the virus can cause sores on the face or on the genitals. Sharing eating utensils, razors, towels, kissing and oral sex may spread HSV- 1. Cold sores are found to be more contagious when they are oozing out the fluid. The spread can also occur even when you don’t have blisters. Once you have experienced an episode of herpes infection, the virus lies dormant in the nerve cells of the skin and may become active again at or near the original site of infection. The recurrence of the cold sores can be triggered by fever, menstruation, stress, fatigue and excessive exposure to the sun.


Cold sores often clear up on their own within few weeks. However several types of antiviral drugs can speed up the healing process. These antiviral drugs include: acyclovir, valacyclovir, Famciclovir, penciclovir.

Image Courtesy : Getty

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