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Many people who endure painful and ugly oral fever blisters have wished for a magic pill that would heal their cold sores. The U.S. Food and Drug Administration (FDA) has approved two drugs that may make these dreams a reality - pills that are proven to shorten the duration of a cold sore infection by at least one day. Is it worthwhile to take a drug to treat a condition that is usually considered to be a minor irritation?

"Yes," says Wilma Bergfeld, M.D., of The Cleveland Clinic in Ohio and a spokeswoman for the American Academy of Dermatology. The healing that takes place in even one day is significant, she says. "This means a decrease in skin inflammation, pain and contagium."

Data has shown that people who take a one-day course of treatment with Valtrex® (valacyclovir HCl) caplets experience quicker healing of cold sore outbreaks. The FDA has approved valacyclovir HCl for use in healthy adults for the treatment of cold sores. This is the first oral antiviral drug that is used for only one day and has been proven to shorten the duration of a cold sore outbreak by a little over one day.

The second drug approved for this purpose is Famvir® (famciclovir). If taken at the first sign of symptoms, taking 1500 mg famciclovir once shortens the herpes infection by 2 days.

According to Bergfeld, taking fewer doses of a drug means less chance of a patient having a possible adverse effect. She adds that taking only one dose of a drug, rather than five days of multiple doses per day, is best for patient compliance, cost and safety.

Topical fever blister treatment

Two creams are also approved for the topical treatment of fever blisters. Penciclovir 1 percent cream (Denavir®) is FDA-approved for recurrent fever blisters. It is applied every 2 hours for 4 days. Starting treatment within 1 hour of an outbreak reduces the healing time by 2 days and reduces the symptoms. Penciclovir also shortens the time when viruses are shed. The earlier penciclovir is started the better, but penciclovir is still helpful when started even after vesicles develop.

Acyclovir 5 percent cream (Zovirax®) is also FDA approved for the treatment of recurrent fever blisters. Frequent application of the cream reduces the healing time by about half a day.

Cold sores are very common

More than 90 percent of adults have been exposed to the herpes simplex virus type 1, the most common cause of cold sores. Only 10 percent of those who are infected with the virus will have a cold sore outbreak. Upon first exposure to this virus, the symptoms usually appear in two to 20 days after being infected. Some people will only show symptoms when they are first infected by the virus, while others may have relatively mild or no symptoms upon initial exposure and do not require any treatment.

It is very rare for the blisters to leave a scar after the primary infection has healed. The herpes simplex 1 virus that initially caused the outbreak, however, remains in the body forever. The virus enters a dormant period where it is still present in the nerve cells yet does not exhibit any symptoms.

Many people never experience another outbreak, while others will have a recurrence of cold sores in the same spot or close to the original infection site. New outbreaks can recur as frequently as once every few weeks, although typically, recurring infections are milder than the initial outbreak.

For people who experience severe symptoms or for those who have recurring cold sores, treatment with antivirals may be of real benefit since without treatment cold sores can take seven to 10 days to heal.

An oral cold sore outbreak may include the following symptoms:

• Warning signs - an itching, burning or tingling sensation on the lips, gums and mouth sometimes occurs approximately two days before the appearance of the cold sores.
• Rash and blisters - cold sores appear in the form of clear, yellowish liquid-filled blisters that may emerge from sore, reddened skin.
• Ruptured blisters - cold sores can break up, allowing the fluid to ooze out and dry to a yellowish crust.
• Healing blisters - cold sores start to heal when the yellowish crust sloughs off and underneath, pink and healthy skin is found.
• Sometimes a few small blisters can merge together to create a larger and more painful cold sore.

External Sources KidsHealth. Coping with cold sores. Accessed May 15, 2007. MedLinePlus Health Information Web site. Herpes simplex. 2001. Accessed September 14, 2002.

This article was reviewed and updated June 2007.