Why Do Fever Blisters Occur?

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What are fever blisters?

Fever blisters or cold sores are small, painful fluid filled boils that occur mainly around the lips and other parts of the oral cavity like the roof of the mouth and gums. They can also occur on the cheeks, nose and other parts of the face. This can be confused with mouth sores which normally occur inside the mouth while cold sores develop around the lips and outside the mouth. Fever blisters are very common.

Cause of fever blisters:

These cold sores are caused by a virus called Herpes simplex Virus -1 which when enters the body and remains permanently in the body showing periods of activity and dormancy. This is a highly contagious condition which normally spreads through direct contact either by kissing or coming in contact with oral secretions which contain viral particles. Most of the infections occur unknowingly and usually before ten years of age in children. This condition is medically known as Herpes Labialis.

Another strain of virus, also known as Herpes Simplex Virus-2 causes blisters in the genital area. The divisions are not rigid and HSV-1 can cause genital herpes and HSV-2 can cause oral herpes. This virus mainly enters through the mouth and very rarely through the skin. The initial infection once the virus enters the body may be present in the form of an intense inflammatory reaction with vesicle formation leading to painful ulcer formation. This virus goes and lodges itself in the group of nerve cells near the cheek bone. It remains dormant over here for long time and may get reactivated when exposed to stress, trauma, fever and ultraviolet radiations. Individuals whose immunity is suppressed are more prone to these recurrent viral infections. Recurrent episodes of fever blisters are not as severe as the first infection. The blisters tend to occur in the same place as the earlier site.

Approximately 70% of population is infected with this virus and recurrent infections occur in one third of patients. Many a times the virus may permanently remain dormant and show no signs of activity or infection, which mainly depends on the individual’s health status. Exactly what triggers the virus to get activated still remains unknown and many studies regarding the recurrent infections are being conducted.

Prior to blister formation the person may experience a sense of tingling numbness and burning which lasts for 1-3 days followed by blister formation and vesicle formation. This entire infection lasts for 15 days where the crust or scab falls off leaving no scar formation.

Precautions should be taken to avoid any stressful conditions that can trigger an outbreak of fever blisters. Avoidance of contact with a person who has an outbreak of fever blisters is essential. Hygiene has to be maintained at the site of blisters to avoid secondary bacterial infection.


Fever blisters or cold sores are caused by Herpes Simplex Virus-1 and is a highly contagious disease which is normally acquired during childhood. The infection spreads by direct contact with the saliva containing the viral particles. Once the virus enters the body, it remains forever in the body producing episodes of fever blisters on and off. In some individuals apart from the initial infection, the virus may remain dormant forever without any future outbreaks. Stress, trauma and fever are aggravating conditions that can cause outbreak of fever blisters. There is no permanent treatment other than palliative measures for pain and blisters. Early treatment and care of fever blisters can reduce the discomfort.

Author: rachita

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