The herpes virus, an ancient and unwelcome human companion, comes in more than one form. Herpes simplex 1 is almost always the culprit in cold sores or fever blisters that erupt around the mouth; herpes simplex 2 is generally responsible for genital herpes. But, in fact, both forms of the virus can cause eruptions on the genitals and around the mouth.
Herpes outbreaks are usually painful and unsightly, as well as contagious. Anywhere from 60 to 90 percent of us carry herpes simplex 1, probably as a result of childhood infection. Genital herpes is one of the most common sexually transmitted infections. Once you have the virus, you have it. It may lie dormant, but it doesn't go away. And it can be spread, even if you have no signs of the infection.
In the 1980s, before there were effective drugs for herpes, the amino acid lysine was regarded as a potential treatment and preventive. One of the building blocks of protein, lysine is supplied by many foods—notably red meats, fish and dairy products. You can certainly satisfy your needs for lysine from dietary sources. But to fight herpes, you would need more, the thinking ran.
The idea that lysine might work against herpes has some plausibility. In order to replicate, the herpes virus requires arginine, another amino acid that's common in foods and necessary to human life; lysine is thought to interfere with the absorption of arginine in the intestine.
However, it's a long way from this observation to a herpes treatment, and most studies on high doses of lysine as a preventive or treatment have been inconclusive. While a few studies have found that lysine decreases the severity or duration of an outbreak, others have not. In any case, most of the studies have been small and poorly designed. What's more, serious side effects (notably kidney problems) from long-term use have been reported; high doses can cause abdominal pain and diarrhea.
We do not recommend lysine. Its effect is unproven, at best, and there are medications that work. A caution: If you do take lysine supplements, don't take them continually, but only when you feel cold sores coming on.
Medication options for cold sores
Fortunately, there are safe and effective drugs for herpes. Commonly used for genital herpes, they can also be used to treat cold sores as well as to suppress future outbreaks. The oral prescription drugs are acyclovir (brand name Zovirax), valacyclovir (Valtrex) and famciclovir (Famvir), all available in generic form. Acyclovir is also available as a cream, as is another prescription drug, penciclovir (Denavir); the creams do not work as well as the oral medications. The cream docosanol (Abreva) is sold over the counter. These do not cure herpes in the sense that antibiotics cure bacterial infections, but do reduce the severity of outbreaks and have few, if any, serious side effects. And long-term daily oral doses can cut down on recurrences.
Final note: To head off cold sores, a sunscreen, applied to the lips daily, can be useful. Sunlight seems to activate herpes simplex 1 in some people.