Alternate Names: Cold sore; Fever blister; Herpes simplex - oral

Causes and Risks: Herpes labialis (cold sores, fever blister) is an extremely common disease caused by infection of the mouth area with herpes simplex type 1. Most Americans are infected with the type 1 virus by the age of 20. The initial infection may cause no symptoms or mouth ulcers. The virus remains in the nerve tissue of the face. In some people, the virus reactivates and produces recurrent cold sores that are usually in the same area but are not serious. Herpes virus type 2 usually causes genital herpes and infection of babies at birth but can also causes herpes labialis.

Herpes viruses are contagious. Contact can occur directly, or through contact with infected razors, towels, dishes, etc. The herpes virus can also infect the fetus and cause congenital abnormalities.

The first symptoms usually appear 1 or 2 weeks after contact with an infected person, or up to as late as 20 or more days after exposure. The lesions of herpes labialis usually last for 7 to 10 days, then begin to resolve. The virus may become latent, residing in the nerve cells, with recurrence at or near the original site. Recurrence is usually milder. It may be triggered by menstrual periods, sun exposure, illness with fever, or other unknown causes.

Prevention: Avoid direct contact with cold sores or other herpes lesions. Minimize the risk of indirect spread by thoroughly washing items in hot (preferably boiling) water before re-use. Do not share items with an infected person, especially when herpes lesions are active. Avoid precipitating causes (especially sun exposure) if prone to oral herpes.

Symptoms:

• warning symptoms of itching, burning, increased sensitivity or tingling sensation may occur about 2 days before lesions appear
• skin lesion/rash
  • located around the lips, mouth, and gums
• small blisters (vesicles), filled with clear yellowish fluid
  • blisters appear on a raised, red, painful skin area
  • blisters form, break, and ooze
  • yellow crusts slough to reveal pink, healing skin
  • several smaller blisters may merge to form a larger blister
• mild fever (may occur)

Signs and Tests: Diagnosis is made on the basis of the appearance and/or culture of the lesion. Examination may also show enlargement of lymph nodes in the neck or groin.

Viral culture or Tzanck test of the skin lesion may reveal the herpes simplex virus.

Treatment: Untreated, the symptoms will generally subside in 1 to 2 weeks.

Antiviral medications such as acyclovir may be given by mouth. They may shorten the course of the symptoms and decrease pain. Wash blisters gently with soap and water to minimize spread of the virus to other areas of skin. An antiseptic soap may be recommended. Ice or warmth to the area may reduce pain. Take precautions to avoid infecting others (see Prevention).

Prognosis: Herpes labialis usually disappears spontaneously in 1 to 2 weeks. It may recur. Infection may be severe and dangerous if it occurs in or near the eye, or if it happens in immunosuppressed people.

Complications:

• spread of herpes to other skin areas
• secondary bacterial skin infections
• recurrence of herpes labialis
• generalized infection--may be life threatening in immunosuppressed people, including those with atopic dermatitis, cancer, HIV infections
• blindness (herpes infection of the eye is a leading cause of blindness in the U.S. because it causes scarring of the cornea)

Call for an appointment with your health care provider if symptoms indicate herpes labialis and symptoms persist for longer than 1 or 2 weeks.

Also call if symptoms are severe, or if you have a disorder associated with immunosuppression and you develop herpes symptoms.