Cold sores are painful blisters that usually occur on the lips, but can develop anywhere from the lips to the nostrils. These sores, technically known as herpes labialis, are caused by the herpes simplex virus type 1. Although the virus continually exists in an affected person's body, cold sores can be triggered by sunlight, stress, fatigue or illness. Some people have frequent outbreaks. The amino acid l-arginine is thought to be one factor in cold sore occurrence.
Two types of herpes simplex virus are responsible for cold sores and genital herpes. HSV type 1 most often causes cold sores and type 2 most often causes genital herpes. Cold sores usually last one or two weeks, gradually forming a crust and scab before healing. Cold sores tend to be painful, especially if touched or bumped.
Taking l-lysine supplements regularly can prevent outbreaks of both cold sores and genital herpes, according to the University of Maryland Medical Center. L-lysine is an essential amino acid, meaning it's one of the amino acids the body cannot produce, so people must obtain it through diet. Lysine occurs in foods with protein, such as meat, fish, eggs and dairy products, but supplements provide a larger amount. The UMMC cautions that not every study has shown positive results for cold sore prevention when using lysine supplements.
The Lysine-Arginine Connection
L-lysine and another amino acid, l-arginine, share common pathways in the body, and l-arginine suppresses l-lysine. This means that consuming high amounts of arginine can lower lysine levels. Some people theorize that this can lead to cold sores in susceptible individuals, as noted by the American Social Health Association. However, no clinical evidence with humans supports the idea that reducing arginine-containing foods in the diet can prevent cold sores, according to the ASHA.
Laboratory research published in the journal "Chemotherapy" found that an arginine deficiency suppressed replication of the herpes virus in tissue culture. Arginine has viral growth-promoting activity, and lysine antagonized that action. People prone to herpes sores might benefit from avoiding large amounts of dietary arginine and also by supplementing with lysine, especially during times of stress, as noted by the study authors.
Although the ASHA does not encourage anyone to stop eating foods containing arginine, it does encourage a diet adjustment if frequent outbreaks of cold sores seem food-related. You might consider taking lysine supplements and avoiding foods high in arginine as soon as initial symptoms appear. These foods include nuts and nut butters, seeds, chocolate, carob, coconut, raisins, gelatin, whole grains, lentils, soybeans, spinach, watercress and seaweed. Some foods, such as meat and dairy products, also contain arginine but have higher amounts of lysine, so those are acceptable.