The People's Perspective on Medicine

Can L-Lysine Prevent Painful Cold Sores?

Readers report that the supplement L-lysine can help prevent recurrent fever blisters caused by HSV-1.
Closeup of a  common cold sore virus herpes.

Cold sores are painful lesions on or near the lips. Sometimes people call them fever blisters because they have a fluid-filled appearance and because an infection with a fever may bring them on. The common virus herpes simplex 1 (HSV-1) causes cold sores. Scientists don’t seem to know why this virus can hide out for months or years without causing a visible problem and then an event triggers the formation of an unsightly, uncomfortable blister. People who have recurrent cold sores can prevent them with antiviral medications like acyclovir (Zovirax) or famciclovir (Famvir). Does taking the supplement L-lysine prevent their appearance as well?

How Can You Treat a Cold Sore?

Q. For years, I was susceptible to cold sores from eating too much sugary food, from stress and from sun exposure.

In my early 30s, I was picking up a prescription for acyclovir ointment my dentist prescribed for a cold sore. The pharmacist told me to take daily doses of the amino acid L-lysine. Once I started taking it, my cold sores stopped almost completely. I hardly get them anymore, although I know I still have the virus in my system.

L-Lysine to Prevent Cold Sores:

A. We have heard from many other readers that L-lysine supplements can help prevent the development of cold sores. There is, unfortunately, little research on the use of this amino acid as a cold sore remedy. However, a review concluded that in combination with a low-arginine diet, high doses of L-lysine can prevent lesion recurrences (Integrative Medicine, June 2017). 

We would like to see large, well-controlled, long-term trials to assess the success of this approach. However, there is little, if any, financial incentive for a drug company to conduct such research.

Another Reader Praises L-Lysine:

You are not the only person to find L-lysine helpful in controlling fever blisters. Years ago, we heard from this reader.

Q. More than 20 years ago I came across an article promoting L-lysine as a preventive measure against cold sore outbreaks. Having suffered with this virus since adolescence, I was motivated to try the supplement.

In my experience, L-lysine is a miracle drug. I used to have at least one outbreak a month, but I now only feel the initial “tingle” of a cold sore if I have overindulged in caffeine, been under an abnormal amount of stress or spent too much time in the sun. I take 1000 mg a day, every day. If I feel an outbreak coming, I triple the dose for a couple of days and the outbreak is prevented.

A. Many people report, like you, that L-lysine seems helpful in preventing or healing cold sores. Double-blind studies on L-lysine for cold sores have produced mixed results. Moreover, there has been surprisingly little research in recent years. This amino acid appears relatively safe, although some people report digestive upset at high doses.

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    About the Author
    Terry Graedon, PhD, is a medical anthropologist and co-host of The People’s Pharmacy radio show, co-author of The People’s Pharmacy syndicated newspaper columns and numerous books, and co-founder of The People’s Pharmacy website. Terry taught in the Duke University School of Nursing and was an adjunct assistant professor in the Department of Anthropology. She is a Fellow of the Society of Applied Anthropology. Terry is one of the country's leading authorities on the science behind folk remedies. .
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    • Mailoo VJ & Rampes S, "Lysine for herpes simplex prophylaxis: A review of the evidence." Integrative Medicine, June 2017.
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    I’ve been taking L-Lysine (which is a trace amino acid) since I contacted cold sores from my ex-husband in 1980.
    It takes about 1-2weeks to build up in your system. Since it attacks all viruses, a side benefit is that I rarely get colds or flus either.

    I haven’t had a flu shot in about 30yrs except for 1 time when my Mom said that a severe flu virus was going around and insisted I get a flu shot. Unfortunately, I did get the flu about 2days after the flu shot!!
    I decided never to get another flu shot again and haven’t had the flu since.

    Because of my experience with trace amino acids I started experimenting with L-Theanine (which was hard to find at most stores back then) and have found it to be very effective at helping me get thru some stressful periods in my life.

    I’ve since tried other trace amino acids for various reasons but I’ll never stop taking L-Lysine, and everyone I’ve recommended it to has had outstanding results as well. It’s natural & has no side effects… what’s not to love about that ?

    I have relied on Lysine for decades as an immediate and effective CURE for cold sores. Immediately when I feel one coming on, I take three Lysine tablets. Thereafter for three to five days, I take one three times a day. If the sore is caught early, it does not develop. If it is caught in progress, it remains in the state it developed to, without getting worse. I ALWAYS carry Lysine when I travel.

    I am a big believer in lysine. I used to get a cold sore nearly every month. Once I feel the “tingle” I take 1000mg lysine 3x a day. It stops it in its track. I’m also prone to mouth sores, and lysine stops those also. I call it a miracle drug without side effects.

    In my early 20’s I had an older co-worker tell me to take L-lysine for sore throat pain and the mouth lesions I often get from sipping soda directly from the can. I’m now in my 50’s and swear by L-lysine for anything mouth related, it works wonders on me and my family.

    Is there any danger in taking lysine for more than a short time period? I have read that it should not be taken except when a breakout is imminent.

    I am reading these articles on Herpes, dementia and l-lysine with interest. Is there any evidence that genital herpes might respond same to l-lysine and if there is a similar risk of dementia from genital herpies?

    It’s sure made a big difference for me. I’ve gone for over a year without any breakouts, and when I even think one is coming on I immediately have my prescription filled. That means healing takes place overnight instead over a week.

    * Be nice, and don't over share. View comment policy^