Fever Blisters

Fever blisters are caused by the two types of herpes simplex virus. Most fever blisters are caused by herpes simplex virus 1, or HSV 1, which causes oral herpes. The virus that causes genital herpes, HSV 2, may also cause fever blisters.

The two stages of oral herpes are primary infection and recurrence of infection. At some time during childhood, most people come down with the primary infection. The individual may or may not have symptoms. This primary infection takes about 2 weeks to clear up. After that, the virus remains in the body but is inactive.

After this primary infection, there can be a recurrence at any time. Many outbreaks occur without any obvious reason. However, the following factors may trigger a recurrence:

• dental work
• emotional stress
• exposure to sunlight
• fatigue
• an upper respiratory infection, such as a cold or flu

Someone with an active oral herpes infection may have the following symptoms:

• numbness or tingling in the area of the outbreak starting hours to a day prior to the outbreak (called a prodrome)
• difficulty eating
• fatigue
• fever
• malaise, or a vague feeling of illness
• sore throat
• tiny blisters that grow into larger sores in the mouth, on the tongue, or on the lips

Fever blisters are caused by a herpes virus. People in the following categories may be more at risk for oral herpes:

• people undergoing radiation therapy or chemotherapy
• people with cancer or other debilitating diseases
• people with HIV or other immunodeficiency disorders

The virus that causes fever blisters can be passed from person to person. Someone with oral herpes should not share lipstick, utensils, or drinks with others. Touching and kissing can also spread the virus, as can oral sex.

Herpes is generally diagnosed with a medical history and physical exam. There are laboratory tests for this virus, but they are seldom needed.

Fever blisters cause no serious long-term effects. The virus will stay in the person's body indefinitely.

The herpes virus can be spread from person to person much like a cold or flu. Sores also can be spread to other parts of the body such as fingers or eyes. Sometimes sores can also spread to the genitals.

In most cases, fever blisters are self-limiting. They will usually crust over and go away in about 2 weeks. If they last longer, the healthcare professional should be consulted.

Treatment for oral herpes includes the following:

• diluted, or 1 1/2%, hydrogen peroxide mouth rinse
• lip balm to soothe sores on the lips - although lip balms with camphor, menthol or flavorings may be irritating to the lips
• penciclovir cream (i.e., Denavir)
• prescription antiviral medicines, such as acyclovir (i.e., Zovirax), valacyclovir (i.e., Valtrex), and famciclovir (i.e., Famvir). These medications can be started during the prodromal period and may prevent the outbreak or lessen the intensity or duration of the outbreak.
• salt-water rinse, with 1/2 teaspoon salt in 8 ounces of warm water
• sunblock cream for lip protection

Antiviral medications may cause nausea, vomiting, diarrhea, and allergic reactions. Creams and ointments may cause an allergic reaction in some individuals.

The sores usually clear up and go away in about 2 weeks. If they last longer than this or if they come back often, the healthcare professional should be consulted.

Any new or worsening symptoms should be reported to the healthcare professional.