David L. Katz, MD
Photo: Mackenzie Stroh
Q: Are there any foods I can eat—or avoid—to help prevent cold sores?
— L. Kelley, Vancouver, Washington

A: Cold sores are caused by the herpes simplex virus. It lies dormant in the roots of nerves waiting for a moment when your immune system is taxed by stress or until it's triggered by your menstrual cycle or an infection like a cold or flu. That's often when the virus shows up—as a sore. You can suppress frequent outbreaks—or shorten their duration—with prescription (Zovirax, Valtrex) and over-the-counter (Abreva) drugs. A lysine supplement—1,500 to 3,000 milligrams per day—may help as well. But you can also reduce the risk of attacks by managing stress, getting adequate sleep, staying fit, and, yes, eating properly. The herpes virus replicates with the help of the amino acid arginine, so avoid foods rich in this substance—chocolate, most nuts and seeds, peanuts, spinach, and grains—when you are fighting an infection or under a lot of stress.

You might also try applying honey: Researchers in the United Arab Emirates found that when placed directly on the sore, honey appears to work as well as or better than topical prescription drugs in shortening the outbreak and speeding recovery.

David L. Katz, MD, is director of the Yale-Griffin Prevention Research Center and president of the nonprofit Turn the Tide Foundation.