What Causes Fever Blisters – Fever Blisters On Lips

Fever blisters are caused by the herpes simplex virus (HSV). They are also known as the cold sores. They occur on the skin very commonly due to the HSV virus.

HSV-1 causes fever blisters more commonly than the HSV-2. HSV-1 is responsible to cause infection in areas above the waist, whereas HSV-2 cause skin infections below the waist.

Fever blister is a very common condition to occur and is seen to occur in more than 85% of the general population all over. When the fever blisters occur first, it can cause immense pain and last for a longer time than during recurrent attacks.

The HSV can cause infection in the face area, in the mouth, on the buttocks, the genitals, anal area and on the skin in general.

In some individuals the HSV may be completely asymptomatic while in others they produce painful blisters. The blister formation is mostly seen in the area from where the virus gains entry into the body. The lesions caused by the HSV disappear completely but they have a high chance of recurrence. When the lesions disappear, the virus tends to settle in the areas deep into the nerve root (ganglion) which is responsible for supplying the affected area, due to any trigger factor they may reappear. The stage at which the HSV remains inactive is known as its latent stage.

The most common locations for the fever blisters to occur are the mouth and the lip areas.

The following factors can cause the fever blisters to reappear:

-any kind of stress

-fever or a flu in general

-any kind of trauma to the affected area

-any changes in the immune system of the body

-many a times the cause is idiopathic

Factors responsible for the spread of the infection:


Fever blisters are very contagious. The person suffering is believed to be most contagious when he has an ongoing active infection. They easily spread by:


-any kind of close contact from the suffering person

-through saliva, so sharing of foodstuffs or sharing utensils can spread the infection




-blisters appear

-the skin may be dry and itchy

-the skin on which the blisters appear is generally red

-a typical tingling or a burning sensation is felt on the skin on the area on which the blisters appear subsequently

-there may be bleeding gums, painful sores on the lips and the mouth area


-difficulty in eating and swallowing


The blisters typically last for about 2- 6 weeks. The lesions heal completely without any scar formation.

When the conditions recur they form fluid filled painful blisters. Although fever blisters affect the oral cavity most commonly, they are also found on the lips- herpes labialis, on the finger tips- herpetic whitlow, on the face neck and arms- the condition is known as wrestler’s herpes. These kind of recurrent lesions take about 10 days to heal.



The diagnosis of the fever blisters can be made on the clinical appearance of the lesions and the patient history. The diagnosis can be confirmed with the help of virus cultures and PCR tests.



No vaccines for HSV are available yet. But drugs like acyclovir, docosanol improve the healing time. Topical anesthetics like lidocaine and benzocaine will help in relieving the symptoms such as pain, burning sensation etc.

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