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The hard, cold facts about cold sores

I occasionally get painful cold sores on my lips, and lately they seem to be happening more frequently. What is causing these cold sores, and what can I do to prevent them?

Cold sores, also called fever blisters, are a painful viral infection caused by the herpes simplex virus (HSV-1). The virus is related to, but is not the same as, the HSV-2 virus, which causes genital herpes. Once contracted, the virus remains in the human body for life.

Most cold sores usually last for a period of 6 to 10 days. A cold sore usually begins with a tingling or itching in the affected area, followed by a small, bubble-like lesion that reaches the blister stage within 24 hours. Cold sores may show up anywhere on the body, but are most likely to appear on the lips or adjacent skin.

According to Lynne Goldberg, M.D., associate professor of dermatology and pathology at Boston University School of Medicine, cold sores are a common occurrence. "Ninety percent of all people get at least one cold sore in their lives, and the first occurrence is generally pretty severe," she says. "A fever, flu-like symptoms and swollen lymph nodes in the neck often accompany the first attack, but recurrent sores usually don't produce these symptoms." Some initial infections cause no symptoms.

Although many people develop antibodies after the first infection and never develop another cold sore, nearly 40 percent of American adults are plagued by recurring cold sores. "People don't realize how highly contagious cold sores are," says Goldberg.

Cold sores are spread through direct contact with an infected person. However, the virus can be spread from the infected person only if it is active. Cold sores are usually transmitted by kissing an infected person or sharing eating utensils, towels, or razors. It is also possible to transmit a cold sore to a person's genitals via oral sex. Once a person is infected, the virus lies dormant in the nerve ganglia beneath the skin's surface, waiting to be reactivated.

Changes in weather and exposure to excessive sunlight, especially during the summer months, can bring on outbreaks, says Goldberg, but stress is the biggest trigger for cold sores. "When you get stressed, your resistance to disease drops, and that can awaken the dormant herpes virus within your nerve ganglia cells, prompting an outbreak."

General precautions must be taken when experiencing a cold sore outbreak. You must always be sure to wash your hands after touching a cold sore, and to avoid kissing and oral sex until the lesion is fully healed. You must also keep your hands away from the eyes after touching a cold sore in order to prevent corneal herpes, which may lead to blindness if left untreated.

"While there isn't an accepted cure for cold sores," Goldberg says, "there are ways a person can try to minimize discomfort or shorten the duration of an attack. "Topical medications are generally less effective than oral prescription antiviral medications like Acyclovir and Valtrex," she says, "which are more effective, especially when started immediately at the onset of a cold sore." Daily antiviral medication is sometimes indicated for patients with frequent cold sores (more than six to eight a year).

"Health Matters" is written in cooperation with staff members of Boston Medical Center. For more information on cold sores or other health matters, call 617-638-6767.

9 March 2001
Boston University
Office of University Relations