A connection between cold sores (caused by herpes simplex virus type 1 or HSV-1) and Alzheimer disease has been tossed around for decades. You can read more about it here. How good is the evidence? Some readers have used L-lysine for cold sores. They would like to know if this supplement might be worthwhile to reduce the risk for Alzheimer disease.
Could L-Lysine for Cold Sores Prevention Also Help Prevent Alzheimer Disease?
Q. I had chicken pox as a child and shingles as an adult. I have gotten the Shingrix vaccine.
For an occasional cold sore, I use acyclovir, but I take L-lysine daily for prevention. Has anyone studied this as an alternative prevention against Alzheimer disease (AD)?
As I understand it, herpes virus might be a contributing factor. Since L-lysine is available without a prescription in the US, it could be an alternative to antiviral drugs for many people.
A. The link between herpes virus infection and AD is tantalizing, but it has not yet been firmly established. What we know about L-lysine is that it can help reduce outbreaks of cold sores due to herpes (Viruses, June 2, 2023). According to the scientists, the effective dose of this dietary supplement is at least 1 gram per day. We found no studies of L-lysine being used to prevent AD.
L-lysine is an essential amino acid. Another amino acid, arginine, counteracts the antiviral action of lysine. As a result, L-lysine appears to be more effective if people reduce their intake of arginine from sources such as legumes, nuts and meat like turkey, chicken or pork.
The Value of Vaccine:
It was smart of you to get vaccinated against shingles. The varicella zoster virus that causes both chicken pox and shingles has also been implicated in AD. Studies in Wales and Australia indicate that older people vaccinated against shingles are less likely to develop AD than their neighbors who were not vaccinated (Nature, April 2, 2025; JAMA, April 23, 2025).
How Can You Cut the Chance of Alzheimer Disease?
Q. I have a family history of Alzheimer’s and have been doing a lot of research on how to try to prevent it. I just read that cold sores and other infections may contribute.
This is quite upsetting to me as I get cold sores frequently. I have started using L-lysine tablets to reduce outbreaks. Is there any evidence that it will protect my brain?
A. A recent study from Harvard offers a novel theory on Alzheimer’s disease (Science Translational Medicine, May 25, 2016). The conventional view holds that plaque made of harmful beta-amyloid protein destroys neurons. That is why drug companies have focused on compounds that can clear plaque out of the brain.
The new hypothesis suggests that beta-amyloid protein is part of the body’s immune response to pathogens as varied as those that cause cold sores, Lyme disease or HIV. It appears to act as a natural antibiotic, but it can cause damage when the immune response goes haywire.
Gina Kolata of the New York Times (May 25, 2016) explains it this way:
“Could it be that Alzheimer’s disease stems from the toxic remnants of the brain’s attempt to fight off infection?
Provocative new research by a team of investigators at Harvard lead to this startling hypothesis, which could explain the origins of plaque, the mysterious hard little balls that pockmark the brains of people with Alzheimer’s.”
Cold Sores (HSV-1) and Alzheimer’s Disease:
For more than 40 years, scientists have been reporting an association between herpes virus infection (HSV type 1) and dementia (Alzheimer’s & Dementia, June, 2015). In the 1980s a pathologist by the name of Melvyn J. Ball, MD, suggested that the virus that causes cold sores invades tissue within the central nervous system called the trigeminal ganglia. He hypothesized that the virus moves in two directions when it is activated. It migrates down nerves to the lips or face to trigger a classic cold sore and may also travel up into the brain to cause damage there in the form of neurofibrillary tangles. You can read much more about Dr. Ball’s research on herpes and Alzheimer’s disease at this link.
Another possibility is that the immune system reacts to the presence of the herpes virus by creating plaques and tables. This is the hypothesis put forth by the Harvard researchers in Science Translational Medicine.
L-Lysine for Cold Sores?
We don’t know whether treating cold sores with L-lysine or antiviral drugs (acyclovir, famciclovir, valacyclovir) would help reduce the risk.
The effectiveness of L-lysine for cold sores was controversial for a long time (Dermatologica, vol. 175, no. 4, 1987). There now appears to be a consensus that this amino acid can help speed healing. It is essential for human health and is a building block for protein formation, but the question of whether it will help beyond herpes outbreaks remains unanswered.
One theory of the antiviral mechanism behind L-lysine for cold sores has to do with its ability to inhibit the action of arginine, another amino acid. Arginine is important in the replication of the herpes virus. Supposedly, L-lysine suppresses HSV-type outbreaks by keeping the virus from multiplying.
Without big, well-controlled clinical trials we are unlikely to get an answer to the controversy of L-lysine for cold sores. After all, no drug company would spend millions on a study for which no profit could be made. In the meantime, all we have are anecdotes. Many visitors to our website do report that L-lysine can help prevent cold sore outbreaks. Here are just a few of the stories we have received over the years:
Janet, Palm Beach County, FL, writes:
“I have suffered with cold sores since I was a child. As an adult, I worked in several hospitals, and the chief pharmacist in one suggested all the possibilities he had heard of that could help.
“It wasn’t until several years later that I heard about L-lysine. I bought it and tried it. What a blessing!
“At the first tingle, I take 1000 mg in the morning and another dose before bed. The blisters never even form! I’ve been caught by surprise when traveling, and by the time I could get to a drugstore the blisters had all formed. By starting out doubling the dose the first day and then dropping back to the 1000 mg level after that, the blisters actually go back down — no sores or scabs.
“Now I’ve found the 500 mg capsules are easier to swallow, and still work as well. Thank heavens for L-lysine for cold sores. I have also heard of several physicians who knew about L-lysine and are recommending it to patients with shingles to help reduce the pain and length of the outbreak.”
Ruth offers this long-term experience with L-lysine for cold sores:
“I had cold sores all the time but then I added 500mg L-lysine to the vitamin that I take. I am 70 years old and have not had a cold sore in 30 years. If I do feel a warm spot on my lip I take an extra 500mg L-lysine and the warm spot disappears.”
Art offers an interesting perspective:
“Q. What’s the difference between love and herpes?
“A. Herpes lasts forever!
“The Herpes Simplex Virus (which was once known as,”The Kissing Disease,” which is why the Roman Empire of old prohibited kissing among their legions) and which some 80% of Americans carry, is what causes cold sores on the mouth.
“Once the virus is initially contracted from an infected person or infected object, the virus travels to, and permanently resides in the trigeminal nerve and reoccurs periodically, usually triggered by stress, certain types of spicy foods, sunlight, etc. in episodic outbreaks.
“The initial outbreak can be quite painful, unsightly, and lasts for 7-10 days.
“Subsequent outbreaks, while still painful, will generally become less severe over the course of time.
What about home remedies?
“Home remedies help alleviate the pain and discomfort and help to shorten the duration of an outbreak.
“L-lysine, an over the counter supplement, works well in the long run by bolstering your immune system. L-lysine is quite affordable and free of any side effects that I know of.
“The home remedies mentioned on the People’s Pharmacy website by contributors to the site, are good for treating the symptoms of herpes labialis, another name for cold sores.
“Whatever works for you I say!”
Other Remedies for Cold Sores:
We have collected lots more home remedies for cold sores on our website. They include kiwi fruit, buttermilk and ice to name just a few. Here is a link. And if you like the idea of home remedies for a variety of common ailments, we encourage you to check out our book, The People’s Pharmacy Quick & Handy Home Remedies. There is a reason why readers have given this our highest rating, 4.9 stars out of a possible 5 stars.
Bettie in Wilkesboro, NC sums it up nicely:
“I love the book. I use the mustard for leg cramps often and it always works; also the cough (Vicks on the feet) which also works). I also tried the raisins before bedtime and only had to get up once [to pee]. Thank you so much.”
Read other comments at this link.
Citations
- Chang JY et al, "A narrative review of alternative symptomatic treatments for herpes simplex virus." Viruses, June 2, 2023. doi: 10.3390/v15061314
- Eyting M et al, "A natural experiment on the effect of herpes zoster vaccination on dementia." Nature, April 2, 2025. DOI https://doi.org/10.1038/s41586-025-08800-x
- Pomirchy M et al, "Herpes zoster vaccination and dementia occurrence." JAMA, April 23, 2025. doi:10.1001/jama.2025.5013
- Kumar DKV et al, "Amyloid-β peptide protects against microbial infection in mouse and worm models of Alzheimer’s disease." Science Translational Medicine, May 25, 2016.
- Lövheim H et al, "Herpes simplex infection and the risk of Alzheimer's disease: A nested case-control study." Alzheimer's & Dementia, June, 2015. DOI: 10.1016/j.jalz.2014.07.157
- Griffith RS et al, "Success of L-lysine therapy in frequently recurrent herpes simplex infection. Treatment and prophylaxis." Dermatologica, vol. 175, no. 4, 1987.
