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What Causes Fever Blisters?

Fever blisters, also known as cold sores, are caused by the herpes simplex virus type 1. This virus lies dormant in nerve cells until triggered by stress, illness, or sun exposure, leading to painful, fluid-filled blisters around the mouth. Want to uncover the triggers and treatments to keep these unwelcome guests at bay? Join us as we explore effective strategies.
Mary McMahon
Mary McMahon
Mary McMahon
Mary McMahon

Fever blisters are lesions in and around the mouth caused by infection with the Herpes Simplex Virus (HSV). They may also be known as cold sores, and they should not be confused with canker sores, sometimes referred to as aphthous ulcers. The causes for these two conditions are different, as are the treatment options.

The form of herpes which causes fever blisters is known as HSV-I, distinguishing it from HSV-II, the form of herpes which infects the genitals. Although HSV-II can cause oral infections and vice versa, most outbreaks of fever blisters are associated with HSV-I. The exact number of infected individuals is unknown, but HSV-I is believed to be extremely common; as many as 50% of people may be infected with it.

Some people get a mild fever with the blisters.
Some people get a mild fever with the blisters.

An HSV-I infection lies dormant until the victim is subjected to stress, sudden changes in diet, fever, or trauma to the mouth. Then, the infection activates, and fever blisters appear. Usually, a few days of tenderness and hard spots precede an outbreak. The unsightly lesions can appear on the lips or around the mouth, and on the gums and roof on the mouth. Inside the mouth, fever blisters tend to be small, and they clear up more quickly than canker sores.

Fever blisters are caused by a common virus, herpes simplex 1.
Fever blisters are caused by a common virus, herpes simplex 1.

Numerous topical medications can be used to treat the pain associated with fever blisters. These medications can also help to shrink the lesions and to promote fast healing. Some people with HSV-I prefer to take medications which suppress outbreaks, or to take medications which are targeted at the early stages of the breakout. No cure for oral herpes currently exists, although scientists are working on it, since this highly contagious disease is so common.

If infected with HSV, you should inform your intimate partners.
If infected with HSV, you should inform your intimate partners.

If you experience recurrent outbreaks of blisters and sores around your mouth, you may want to be tested for HSV-I. Although many people think of this disease as a sexually transmitted infection, you should not feel ashamed. HSV-I is so contagious that it can be passed in a wide variety of ways; you could share a drink with someone and pick it up, for example. If you do test positive, it is important to inform intimate partners so that they are aware that they may be at risk for infection. A doctor can provide advice on reducing and managing outbreaks through dietary and lifestyle modifications.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a TheHealthBoard researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a TheHealthBoard researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...

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Discussion Comments

closerfan12

Are fever blisters contagious? What happens if you kiss somebody while you have fever blisters on your lips? Will they get infected?

FirstViolin

@TunaLine -- There are a lot of fever blisters treatments out there on the market. However, there are also a lot of home remedies for treating fever blisters.

My personal favorite among the fever blisters home remedies is to place a tea bag over the sore for about five minutes, and repeat this every few hours.

If the fever blisters aren't too serious, then you can also try to treat them with ice.

TunaLine

How do I heal fever blisters? I always get these cold sores and fever blisters, and I want to get rid of them ASAP.

Does anybody have any advice for me?

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    • Some people get a mild fever with the blisters.
      By: MAST
      Some people get a mild fever with the blisters.
    • Fever blisters are caused by a common virus, herpes simplex 1.
      By: Marco2811
      Fever blisters are caused by a common virus, herpes simplex 1.
    • If infected with HSV, you should inform your intimate partners.
      By: Artem Furman
      If infected with HSV, you should inform your intimate partners.
    • A person should not feel ashamed if they have an outbreak of fever blisters.
      By: listercz
      A person should not feel ashamed if they have an outbreak of fever blisters.
    • Over-the-counter ointments can be applied directly to a fever blister to promote quick healing.
      By: markcarper
      Over-the-counter ointments can be applied directly to a fever blister to promote quick healing.
    • HSV-I can be passed by sharing drinks with someone.
      By: xixinxing
      HSV-I can be passed by sharing drinks with someone.
    • Applying certain types of mouthwash directly to a cold sore may promote faster healing of the lesion.
      By: theartofphoto
      Applying certain types of mouthwash directly to a cold sore may promote faster healing of the lesion.
    • Topical medications may be used to treat fever blisters.
      By: 3ThousandPhotoSTD
      Topical medications may be used to treat fever blisters.
    • Fever blisters may appear on the lips or around the mouth.
      By: LoloStock
      Fever blisters may appear on the lips or around the mouth.