What causes fever blisters?

Fever blisters are lesions in and around the mouth caused by infection with the herpes simplex virus (HSV). They can also be known as cold sores, and should not be confused with canker sores, sometimes called aphthous ulcers. The causes of these two conditions are different, as are the treatment options.

The form of herpes that causes fever blisters is known as HSV-I, which distinguishes it from HSV-II, the form of herpes that 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; up to 50% of people can be infected with it.

An HSV-I infection remains dormant until the victim experiences stress, sudden changes in diet, fever, or trauma to the mouth. Then the infection becomes active and fever blisters appear. Usually a few days of tenderness and hard spots precede an outbreak. Unsightly lesions can appear on the lips or around the mouth, and on the gums and roof of the mouth. Inside the mouth, fever blisters tend to be small and go away more quickly than canker sores.

Numerous topical medications can be used to treat the pain associated with fever blisters. These medications can also help reduce injuries and promote rapid healing. Some people with HSV-I prefer to take medications that kill the outbreaks, or take medications that target the early stages of the outbreak. There is currently no cure for oral herpes, although scientists are working on it, as this highly contagious disease is very common.

If you experience recurring outbreaks of blisters and sores around your mouth, you may want to get tested for HSV-I. Although many people think that this disease is a sexually transmitted infection, you should not be ashamed. HSV-I is so contagious that it can be spread in a variety of ways; you could share a drink with someone and pick it up, for example. If you test positive, it is important to inform intimate partners so they know they may be at risk of infection. A doctor can provide advice on how to reduce and control flare-ups through diet and lifestyle modifications.

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