What Causes Fever Blisters?

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.

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.

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 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.