For many people, itching, tingling or numbness around the lips signals that a cold sore is on the way. Cold sores are flaccid, painful blisters caused by one of two types of the herpes simplex virus, usually type 1. After three or four days, according to dermatologist Christina Cernik in the June 9, 2008 issue of "Archives of Internal Medicine," they usually rupture, leaving behind a raw, red, weeping sore that takes another week or so to heal. Before the discovery of antiviral drugs in the early 1980s, L-lysine tablets were one of the few options for cold sore sufferers. Today, people with cold sores should start by talking to their health care providers.
Definition
L-lysine is one of 20 amino acids that serve as the building blocks for proteins in the body. Among amino acids, L-lysine is considered "essential" because it plays a key role in the production and repair of collagen, the absorption of calcium and the transformation of fats into energy. The "L" prefix refers to the conformation of the amino acid. Although amino acids also exist in a "D" conformation, humans only use "L" amino acids, so "D" amino acids are not counted or measured.
History
The first published reference to L-lysine as a treatment for cold sores appears in the Jan. 26, 1974 issue of the "Lancet." In it, radiologist Christopher Kagan, M.D. describes a patient who was unable to complete a barium swallow study because of extensive cold sores on and inside the mouth. Kagan claimed that the patient took L-lysine tablets and returned one week later, completely healed.
Dose
L-lysine occurs naturally in foods such as meat, poultry, milk, fish and legumes. The amount of lysine required to treat cold sores, however, exceeds what a person can reasonably obtain from foods. To treat or prevent cold sores, the University of Pittsburgh Medical Center recommends taking 3 g of L-lysine per day in the form of supplements. The University of Maryland Medical Center actually recommends the same dose to prevent cold sores, but a higher dose --- up to 9 g per day --- to treat them. Both recommend dividing the total dose into three or more smaller doses taken throughout the day, in order to maximize the amount of L-lysine that the body ultimately absorbs.
Source
L-lysine tablets are sold at most grocery and drug stores. Patients should look for products that claim "USP" verification. USP stands for "United States Pharmacopeia," a non-profit organization that reviews and certifies dietary supplements and other products that meet standards for quality, purity, strength and consistency. This is particularly important because, unlike prescription and over-the-counter drugs, L-lysine and other products marketed as dietary supplements are not subject to approval by the U.S. Food and Drug Administration.
Safety
L-lysine supplements may make heart, liver, kidney and gallbladder disease worse and interfere with protein metabolism in children and women who are pregnant or nursing. People in these groups should not take L-lysine except as directed by a doctor. L-lysine does not replace conventional medical treatment for cold sores or any other condition. As with any other dietary supplement, people who use it should share this information with their health care providers. Although cold sores usually resolve with no treatment at all, people who experience severe, frequent or long-lasting --- longer than 14 days --- outbreaks should see a doctor.
Effectiveness
The University of Pittsburgh Medical Center website describes L-lysine as a "famous" treatment for cold sores and reviews seven clinical trials on its use. In one of these trials, a 1987 study published in the journal "Dermatologica," 52 patients who took 3 g of L-lysine per day for six months experienced significant reductions in the frequency, severity and duration of cold sore outbreaks compared to patients who took a placebo. Two other studies reported similar results that failed to achieve statistical significance. Four other studies that used lower doses of L-lysine found no effect at all.
References
- "Archives of Internal Medicine"; The Treatment of Herpes Simplex Infections; Christina Cernik, M.D. et al.; June 9, 2008
- "Lancet"; Letter: Lysine Therapy for Herpes Simplex; Christopher Kagan, M.D.; Jan. 26, 1974
- University of Pittsburgh Medical Center: Herpes
- University of Pittsburgh Medical Center: Lysine
- University of Maryland Medical Center: Lysine
- United States Pharmacopeia: About USP
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