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How Good Is L-lysine Against Cold Sores?

The science is not very supportive when it comes to L-lysine against cold sores. But many readers say it works surprisingly well against outbreaks.
How Good Is L-lysine Against Cold Sores?

Cold sores are painful. They are also unsightly. Perhaps more alarming, there is some research to suggest that cold sores may increase the risk for Alzheimer’s disease (see this link). Could L-lysine for cold sores protect the brain from dementia? See this link for a response to that question. A reader wants to know that the science is behind L-lysine against cold sores.

Q. I’ve had cold sores since I was young. I have spoken with doctors about them innumerable times.

In your column, you often recommend taking L-lysine. This product has not shown efficacy in peer-reviewed clinical trials, as far as I’ve heard. It is just one of the home-remedy folk “cures” that show up in your columns. Even acyclovir and valacyclovir are of limited efficacy.

A. Cold sores are caused by herpes simplex virus type 1. It hides out in the body and appears in the form of a cold sore lesion on the lips or face in the event of a drop in immunity, exposure to intense sunlight or increased stress (BMJ Clinical Evidence, online Sep. 23, 2009).

A comprehensive Cochrane review supports your stance on L-lysine against cold sores (Cochrane Database of Systematic Reviews, Aug. 7, 2015).  That could be due to a lack of studies rather than a lack of efficacy, however. Long-term use of the antiviral drugs acyclovir or valacyclovir was modestly effective in preventing cold sores.

Stories About L-lysine Against Cold Sores:

Despite such negative news, we continue to hear from readers that L-lysine works for many people. Here are just a few testimonials:

“Lysine tablets work for me. At the first tingle of a beginning cold sore, I take a 500 mg tablet. Then I take another 500 mg tablet later on that day.
“I try to take 1000 mg a day for several days. By then, there is either a small cold sore that goes away early or else no cold sore at all. Usually it’s the latter.”

Gael brings her biochemistry background to bear:

“I find L-lysine against cold sores to be very effective. I read recently that prevention is best, so I now take a 1,000 mg tablet each morning with breakfast.

“Having studied biochemistry long ago, I hypothesize that the herpes virus needs arginine to build its protein coat. Lysine is similar in structure to arginine; perhaps when there is more lysine than arginine, it inhibits the virus’s ability to replicate. If I do get the beginnings of a cold sore, I increase the dose to one tablet with each meal. I also try to avoid foods high in arginine, such as nuts and chocolate, when I have a cold sore.”

Nat has an interesting regimen to share:

“I used to get cold sores at least once every 2 months. And when I would have an outbreak, there would not be just one, but a whole CLUSTER of them in the same spot. So embarrassing and painful.

“I heard of L-Lysine and have been taking it. I don’t take it every day. As and when needed.

“If I look closely in the mirror and see a slight color change or texture change on my lips I take a 500mg tablet before bed or whenever I noticed it.

“When I feel like one is coming on I would up the dose to 1000 mg. DOES THE TRICK!

“I am not joking. Two days ago I woke up with the tell-tale bubble on the lip. I put ice in a sandwich bag and held the ice on my lip for 3 minutes (it kills the pain; feels like frostbite but helps to reduce the newly forming cold sore under the skin). Then I doused it with acyclovir antiviral cream. (I put a thin layer on if I am going to work; otherwise it’s embarrassing).

“Then as SOON as I saw it, I took 1000mg L-lysine. I find the cold sore diminished throughout the day. After work I slathered on cream and went to bed and the next morning. GONE!”

Share your own experience with L-lysine against cold sores in the comment section below.

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.” .
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