Cold sores, which are sometimes called fever blisters, crop up on the lips or on the face near the mouth. In addition to being painful, they are unsightly. Cold sores are caused by the herpes simplex 1 virus that can lie in wait for months or years before re-appearing. Many readers have told us that they can side-step a cold sore by taking L-lysine at the first hint of one developing.
Will Taking L-Lysine Avert a Cold Sore?
Q. I have been taking L-lysine for years and I can’t remember my last cold sore. I had shingles one time many years ago and took L-lysine daily. It took one day for the pain to end and about two days for the rash to disappear.
I explain the efficacy of lysine this way: Herpes viruses cause both cold sores and shingles. They require the amino acid arginine to replicate itself. Somehow, the viruses recognize lysine as if it were arginine. The lysine prevents viral replication.
A. Your explanation is plausible, as supported by research on the herpes simplex virus 1 (Journal of Virology, June, 2009). Herpes virus is reactivated by an enzyme, lysine-specific demethylase 1 (Science Translational Medicine, Dec. 3, 2014). We don’t know how L-lysine affects that enzyme, but presumably there is some interaction.
Studies Are Lacking on Taking L-Lysine:
Sadly, there have been very few well-controlled trials involving L-lysine for cold sores. Most studies hav focused on the use of antivirals to prevent or treat herpes infections (Cochrane Database of Systematic Reviews, Aug. 7, 2015). The Cochrane Review of the research found that drugs such as acyclovir and valacyclovir do seem to help prevent cold sores modestly.
L-Lysine to Prevent Cold Sores:
Q. All through high school I suffered with cold sores. This continued until I discovered L-lysine as a young adult. Since I started taking it daily, I’ve had no more cold sores.
If I run out and miss a day or two, I get slight tingling and even a small cold sore. I immediately get my refill of L-lysine, and the cold sore goes away. I’m not aware of any ill effects from L-lysine. It has been a great help against cold sores.
A. Physicians often prescribe antiviral drugs such as acyclovir, valacyclovir or famciclovir. These drugs speed healing of herpes infections, including cold sores. They can also be taken every day to prevent cold sores.
Hundreds of readers report that taking L-lysine at the first tingle of a cold sore can also be highly effective. Some people, like you, report that this supplement can also prevent an attack. A recent review of research concluded that increasing lysine intake and reducing arginine can prevent cold sores or speed healing (Viruses, June 2, 2023).
Other Readers Offer Testimonials:
Despite the lack of clinical research, many readers have found L-lysine as helpful as you have.
Ana wrote:
“Lysine has keeps me free of my yearly herpes outbreak for more than 10 years. I used to have an upper lip outbreak every summer for as long as I can remember.
“Around 1991 I found an article in a magazine about the effectiveness of lysine for herpes. I tried it the next time I had lesions. They went away in less time than usual.
Years after I read about taking 2 500 mg tablets every few hours at the first symptoms 10 times a day. I kept taking them for several days. It worked by reducing the size of the lesions and the healing time.
“I do not take them regularly, only when I have the symptoms. I did that for years and then I noticed that I was only getting a pinpoint-size pustule that would go away in two or three days.
“I always start the tablets if I feel the characteristic itching or tingling in my chin. I have told others about it and they have reported to me the same success. I always keep lysine on hand, just in case.”
LBP in Dallas reported:
“I, too, found that taking L-lysine the second I felt a tingling in my lip either greatly reduced the cold sore severity or, on rare occasions, stopped it in its tracks. But there seemed to be no way to absolutely prevent cold sores from trying to form. Over the course of my life (I’m 59), I just grew accustomed to watching for tell-tale signs and then ingesting mega-doses of lysine.
“A little over three years ago, I began taking 4,000 mg of vitamin D3 on a daily basis because of all I had read about vitamin D deficiency. A year and a half later, I noticed I had not had any cold sore symptoms AT ALL during that time and I connected it to the D3 I was taking. Today, more than three years later, I continue to be completely free of any outbreaks. I am convinced that the 4,000 mg of D3 daily is responsible and I’m curious as to whether others have experienced similar results.”
We don’t know whether vitamin D could have an effect on cold sores. Sun exposure can often trigger an outbreak.
