Article updated and reviewed by David Aronoff, M.D., Assistant Professor, Division of Infectious Diseases, University of Michigan Medical School on Map 9, 2005.
Herpes is the medical name for a group of similar viruses. This group includes the varicella-zoster virus, which causes chicken pox as well as shingles; the Epstein-Barr virus, which causes infectious mononucleosis (mono); cytomegalovirus (CMV), which is responsible for infections that usually afflict newborns and people with defective immune systems; and the herpes simplex virus (HSV), which causes genital and oral infections.
To most people, however, herpes is the common term for infections caused by HSV.
There are two types of HSV, HSV-1 and HSV-2. In most cases, HSV-1 causes ulcerative lesions of the oral mucosa/lips that are commonly referred to as cold sores or fever blisters. HSV-2, on the other hand, generally causes genital herpes. However, some genital herpes may be caused by HSV-1 virus, and some oral herpes may be caused by HSV-2. This cross infection can happen when sexual partners have oral-genital relations.
Fever Blisters – Cold Sores
Fever blisters or cold sores typically take the form of tiny, clear, fluid-filled blisters on the face (most commonly the lips). They occur on mucous membranes and may also develop in wounds on the skin. Symptoms include painful blisters (vesicles) on the lip or under the nose that ulcerate and crust over. Lesions are sometimes accompanied by fever. A cold sore usually clears by itself in seven to twelve days, and rarely leads to medical complications.
The number of blisters varies from one to a whole cluster. Before the blisters erupt, the soon-to-be-infected skin may itch or become very sensitive. The natural course of the blisters is to break spontaneously or as a result of minor trauma, allowing the fluid contents to ooze. Eventually, scabs form and slough, leaving slightly red skin.
The cold sore is highly contagious and is easily transmitted in saliva or close sexual or social contact.
There are distinct patterns of disease with oral HSV infections, depending on whether the infection is a new one (primary disease) or recurrent. Primary infection with HSV-1 is common, with more than 90% of adults having detectable antibody to HSV-1 in their serum. However, most of these infections occur asymptomatically, with approximately ten percent of patients developing symptoms indicative of a primary infection.
Though the primary infection heals completely, rarely causing a scar, the virus that caused it remains in the body, migrating to nerve cells where it remains in a dormant phase. Many people will not experience another infection or recurrence. Others will be plagued with recurrences, either in the same location as the first infection or in a nearby location.
Recurrent infections, which tend to be milder than primary infections, may be triggered by a variety of stresses including fever, exposure to the sun, and menstruation. However, for many individuals, the recurrences are unpredictable and have no recognizable precipitating cause. The frequency of recurrence can vary dramatically from once every few years to multiple times per year.
It is important to note that there are a few serious complications of oral HSV infection:
Eye infections. HSV may infect the eye and lead to a condition called herpes keratitis, the most frequent cause of corneal blindness in the United States. The inflammation results in the feeling that there is something in the eye, pain, sensitivity to light, and discharge. Débridement, topical antiviral therapy, interferon treatment, or a combination of these methods appear to enhance healing. However, recurrences are common.
Infections in babies. A pregnant woman who has genital herpes at the time of delivery may transmit the virus to her baby as it passes through the birth canal, touching the affected area. The baby can die or suffer severe damage, particularly mental retardation. Women who know that they have had genital herpes or think they might have it during their pregnancies should tell their physicians so preventive measures can be taken. A cesarean section is indicated for some patients. It is estimated that only half of the infants delivered through an infected vagina acquire the disease, but the ones that do are at risk for having a severe infection.
The newborn can also be infected by exposure to the virus from non-genital lesions. If the mother or a person working in the nursery has active blisters on the lips or hands, the baby can become infected. Family members and friends with active HSV should not handle the newborn.
Pregnant women should avoid sexual contact, especially in later pregnancy, with a partner with active genital herpes. The use of condoms can be suggested for those who will not abstain. There is no evidence to suggest that infection of an infant with HSV-1 carries a different risk than infection with HSV-2.
As noted above, HSV infections take the form of blisters or crusted, ulcerative lesions that generally occur periodically, often causing itching and pain.
Treatment of oral HSV lesions can be divided into two categories: 1. non-specific treatments aimed at reducing symptoms of HSV lesions and 2. specific anti-viral therapies meant to hasten lesion healing or prevent recurrences.
If fever blisters erupt, they should be kept clean and dry to prevent bacterial infections. A soft, bland diet is recommended to avoid irritating the sores and surrounding sensitive areas. Care should be taken to refrain from touching the sores and spreading the virus to new sites, such as the eyes and genitals. To prevent infecting others, kissing should be avoided, as well as touching the sores and then touching others. It is important to wash hands after eating or touching one’s mouth.
Ice applied directly to the cold sore site prior to the eruption of a blister may reduce the potential swelling. Wrap an ice cube in a damp cloth and keep it on the area for five minutes. Reapply every hour.
Any drying or astringent over-the-counter cold sore preparation that contains camphor and/or phenol such as Campho-Phenique or Orabase may provide relief if applied in the early stages. When used in the scab stage, these ointments can help prevent painful cracking and bleeding.
Specific antiviral drugs
Oral acyclovir (Zovirax) or the recently developed drugs, valacyclovir (Valtrex) or famciclovir (Famvir), lessen the symptoms and frequency of fever blister recurrences for some patients. These drugs prevent HSV from multiplying and are effective when taken in pill form prior to an outbreak of the virus. Topical antiviral creams containing acyclovir (Zovirax) or penciclovir (Denavir) may also help in limiting the extent or duration of lesions if applied promptly to affected areas.