Does lysine really help stop cold sores?

Odds are if you’ve been looking for a way to stop those icky cold sores from coming back all the time, you’ve heard of lysine.

They say it’s the yang to arginine’s yin.

Some people swear it’s the best thing since orange soda, some think it’s a huge waste of time.

Now, I’m gonna be honest. I’ve always been partial to the latter. I think praying to alien overlords for liberation from this terrible herpes virus would be a more effective solution than taking lysine.

See, my mind was made up when I tried taking lysine myself back when I was getting big nasty outbreaks every few weeks.

Did it help? Not one bit.

The cold sores just WOULDN’T… STAY… DOWN…

Kind of like how Rocky Balboa kept getting back up no matter what Apollo Creed or Dolph Lundgren threw at him (did I just compare the great Sylvester Stallone to herpes? Yes, yes I did.)

Gotta hand it to the damn herpes virus, it’s a persistent little bastard.

Still, I can’t help but wonder why, when and how did lysine become the go to strategy for fighting off cold sores.

And also, does it actually work, or is it a bunch of hooey?

And if it does work, HOW does it fight off the herpes virus (i.e. by what mechanism does it interfere with the activity of the herpes virus)?

A lot of questions to be answered, for sure.

Let’s take a look, shall we.

First things first. What the heck is lysine anyway?

Lysine, also known as l-lysine (or just K for the truly lazy), is an amino acid (i.e. the building blocks of protein).

More specifically, lysine is an essential amino acid, meaning your body is too dumb to make it for itself, so you need to get it through your diet.

Where? Well, basically most animal foods high in protein will contain a good amount of lysine (think meat, poultry, fish, eggs, etc.)

And it’s actually VERY important you do get enough of the stuff.

Because if you don’t, you risk exposing yourself to all the nasty side effects of lysine deficiency.

Lysine… deficiency?

Yes. Turns out, your body needs (not wants, needs) lysine to do a whole bunch of pretty important stuff.

And in fact, lysine deficiency is often seen in vegans who simply don’t get enough because they refuse to eat animal products. That should tell you something right there.

What are the symptoms of lysine deficiency you ask?

It’s a pretty long list:

Plays a major role in protein synthesis. Your body is constantly making new proteins to build and repair tissue. It’s so important in this regard that it can lead to stunted growth in kids who don’t get enough.

Keeps your heart healthy. Ever heard of carnitine? That’s ok. It’s a nutrient that your body needs to keep your circulatory system (i.e. your heart, arteries, veins, etc.) healthy and running smoothly. And to make it, your body needs (drumroll…) lysine. Low levels of carnitine have been associated with increased risks of heart problems.

Helps your body absorb calcium. Without lysine, your body has a hard time absorbing all the calcium it needs from your diet. And if it can’t absorb enough calcium, it can’t keep your bones and teeth strong. Plus, calcium is a major player in the proper functioning of your nervous system, so… yeah.

Helps hold your body together. Your body contains a massive amount of what is called “connective tissue”. It is designed to connect (duh) and bind other tissues together, like a sort of glue holding you together. One of the main proteins required to build connective tissue is collagen and your body can’t make strong collagen fibers without lysine. Plus, lysine is also needed to keep your bones strong and healthy.

Plays an important role in the immune system. Lysine plays a significant role in making sure your body can mount a strong and effective immune response. And what’s more important that a strong immune response when your body is under attack by a virus like say, oh I dunno, HSV-1? Not much.

Now that last point is important to remember. Because if you remember, I said that I DON’T believe taking lysine supplements is very useful for fighting off cold sores.

But how can I still believe that when I just laid out some juicy scientific proof that lysine is super important for the immune system?

Simple. I just don’t believe that taking a gram or two of lysine in supplement form is going to bring you more benefits than the lysine you’re already getting in your diet will (unless of course you don’t eat enough protein on a regular basis).

Why is lysine such a popular treatment for cold sores?

The big question is how and when did lysine become such a ubiquitous treatment for fighting off cold sores?

More importantly, what kind of scientific evidence is there to back it up as a legitimate cold sore treatment?

Let’s break it down.

Just like how the bogus idea that arginine must be avoided at all costs, lysine as a cold sore treatment started to gain popularity in 1978 after a study titled ‘A multicentered study of lysine therapy in Herpes simplex infection‘ was published from a dude named C. Kagan and his team-o-scientists.

But it didn’t stop there.

In 1981 a study titled ‘ Relation of arginine-lysine antagonism to herpes simplex growth in tissue culture’ was published in the journal Chemotherapy. It found that lysine “antagonized the viral growth-promoting action of arginine” in cell cultures (i.e. grown in a Petri dish).

Then in 1984 a team of scientists who gave 1 gram of lysine daily to a group of recurring cold sore sufferers found that lysine did indeed help reduce the rate of outbreaks. The interesting thing is, they suggested that the beneficial effects of lysine happen only in individuals whose serum levels were increased to over 165nmol/ml (meaning they were below that threshold before taking lysine).

In 1987 Griffith et. al. published a paper titled “Success of L-lysine therapy in frequently recurrent herpes simplex infection. Treatment and prophylaxis“. In this study, they gave cold sore sufferer’s either 1 gram of lysine (or a placebo) 3 times a day for six months. They found a significant reduction in the total number and severity of outbreaks the participants experienced.

There are other studies that support the use of lysine for fighting cold sores, but those are the 3 main ones that started the whole shebang.

But of course, there are a few gigantic questions lingering over those there studies…

First of all, those that were performed in human guinea pigs relied on self-reporting to determine the frequency of outbreaks before starting the lysine trials. And the thing about self-reporting events past is, people are notoriously bad at it. Hell, I can’t even remember what I had for lunch yesterday, let alone how many cold sores I had last year.

So just how accurate were the participants in reporting the total number and severity of outbreaks they suffered prior to the trial? And if you don’t know how many outbreaks people ACTUALLY suffered from before, can you accurately state that lysine had a beneficial effect? It’s tough…

Secondly (and more importantly), not a single one of those studies accurately controlled for dietary factors. Meaning the researchers likely had no clue how much lysine the participants were taking in on a daily basis prior to the start of the trial.

Take the 1984 study for example. They reported that the average baseline serum concentration of lysine in participants’ blood (i.e. before taking lysine) was over 170nmol/ml. That’s already higher than reported 165nmol/ml threshold, below which people got more cold sores. I can’t help but wonder whether the participants with serum lysine levels below 165nmol/ml before the study weren’t experiencing some sort of dietary deficiency of lysine.

It could be that the difference they found wasn’t in the fact that lysine specifically helped fight off cold sores. Rather, it could be that the supplemental lysine provided their bodies with a component  crucial for the immune system (hey, it’s called an “essential” amino acid for a reason).

Plus, there was absolutely no controlling for other dietary factors proven to screw with the immune system. Things like sugar, alcohol, smoking, etc. At best, the scientists suggested that the participants avoid “arginine containing foods”. But how many actually did that with any consistency?

However, a lot of studies found that taking lysine doesn’t work

There’s another side to this lysine coin.

Mainly, for every study that found taking lysine helps alleviate the symptoms of cold sores, there’s another that suggests it does nothing at all.

In 1980, a study titled Lysine prophylaxis in recurrent herpes simplex labialis: a double-blind, controlled crossover study tested giving patients 100 mg of lysine daily for 12 weeks. They found that taking lysine had no effect on the recurrence rate of cold sore outbreaks. They also found that it had no effect on the severity of symptoms or the healing rate of the sores.

In 1984, a study titled Failure of lysine in frequently recurrent herpes simplex infection. Treatment and prophylaxis. tried giving 400 mg of lysine 3 times a day to patients. They found it to be highly unlikely that lysine reduces the recurrence of cold sore outbreaks in the majority of patients.

Finally, in 2015 a group of scientists reviewed every single scientific study about cold sore treatments up to 2015 (trust me, these guys dug WAY deeper than what I’m doing here). And in regards to lysine, they concluded that there is absolutely no evidence supporting the efficacy of lysine as a cold sore treatment.

Essentially, when the most up to date scientific evidence (put together by people WAY smarter than little old me) concludes that lysine doesn’t do jack-poop against cold sores, I tend to believe them.

“It’s not about the lysine alone”, they say… “It’s about the lysine to arginine ration”, they say…

I’m sure you’ve heard this too. The die-hard lysine supporters say that what’s important is keeping the lysine to arginine ratio in check, not simply taking more lysine.

The main argument is that apparently, lysine competes with arginine during the viral replication process. So when the herpes virus tries to use arginine to make copies of itself, all it has laying around is lysine. It’s like trying to build a Lego house, but instead of regular 2×4 blocks, all you have are a bunch of little Lego character heads. And stacked heads does not a sturdy Lego house make.

The idea that lysine interferes with arginine during viral replication once again comes from the 1978 study of Dr. Kagan and his team. Basically, they found that the herpes virus had a harder time replicating in cell cultures when both lysine and arginine were present, versus just arginine alone. So the idea became that if you can increase the lysine to arginine ratio (i.e. more lysine and less arginine), you could screw with the replication process of the herpes virus.

For the sake of argument, let’s assume this is true (although data in actual humans, not just in Petri dishes, is kind of lacking on this topic).

From there, the idea of taking lysine supplements and reducing arginine intake came from the idea that lysine and arginine compete for absorption at various points in the body. So, if you take more lysine, you don’t just increase the levels of arginine in your body, you also reduce arginine’s ability to be absorbed.

To figure out if this is true or not, I did some digging into amino acid transporters (the little machines responsible for taking amino acids from your food into your blood) to figure out if taking lysine can actually affect the lysine to arginine ratio in humans. What I quickly found out is that amino acid transporters are an INSANELY complex topic that scientists haven’t fully figured out yet.

But the general consensus is that yes, individual types of amino acid transporters ferry across different kinds of amino acids. So, it appears that lysine and arginine do/could in fact compete for a spot on the “ferry”.

But what I’m wondering is just how much more lysine would you need to swallow to significantly affect the absorption of arginine? I highly doubt that taking 1 extra gram of lysine each day in supplement form (as most people recommend for fighting cold sores) can seriously affect the absorption rate of arginine. I think you’d have to FLOOD your body with the stuff to see any change.

But it ultimately doesn’t matter. See, evidence suggests that taking extra lysine doesn’t affect the levels of arginine floating around in your blood at all. Case in point, a group of scientists looked at the blood levels of both arginine and lysine in people before and after giving them food high in lysine (lysine cookies to be exact). As expected, the lysine levels of the participants increased. But more interestingly, they found that the free arginine levels didn’t change one iota. So the lysine to arginine ratio increased only because lysine increased, not because arginine levels decreased (they didn’t).

What this tells us is that the only way to have a higher ratio of lysine to arginine is to eat more lysine.

However, even if a higher lysine to arginine ratio DOES lower the herpes virus’s ability to replicate (again, data in humans is lacking), it’s not clear by how much you’d need to change it to see any positive effect.

But I say it doesn’t matter because eating more lysine than arginine is something most people do anyway, since we tend to have a preference for high lysine foods like meat and dairy over arginine rich foods like beans and nuts. So most people already have a positive lysine to arginine ratio and taking a single gram of the stuff daily won’t do much to change that ratio.

How much lysine do you really need to consume on a daily basis?

Like I said, lysine is an essential amino acid. Your body can’t make it so you need to eat some.

But the question is, how much lysine do you really need? And more importantly, how much do you need to maintain a healthy immune system that will be able to crush the herpes virus the second it pops its ugly little head out?

Well, according to a report from the World Health Organization, the daily requirement for lysine is at about 30mg per kilogram of bodyweight (so about 13.5mg per pound of bodyweight).

So, if you weigh 150 pounds (68 kilos), that means you need approximately 2000mg of lysine per day. 200 pounds (90 kilos), 2700mg.

For comparison, lysine supplements sold for cold sores often recommend you take up to 3000mg of supplemental lysine per day, which that seems perfectly in line with the recommendations from the WHO, wouldn’t you say?

So in that regard, companies selling lysine supplements for cold sores are right.

Then again, no they aren’t.

See, the problem I have with lysine supplements (and many other supplements for that matter), is that they never seem to take your diet into account when recommending their dosages.

Here’s what I mean.

For the sake of argument, let’s say that the recommended daily dosage of lysine is 3000mg (which is higher than the actual RDA for most people). How much of that is covered by eating breakfast, lunch and dinner?

It’s an important question to answer.

Because lysine is found in a heck of a lot of different foods. From dairy products to meat, poultry and fish, it’s present in basically every source of protein us humans tend to eat on a daily basis.

For example, a single egg contains approximately 250mg of lysine.

One single chicken breast has well over 2000mg of lysine.

One serving of beef contains a hair less than 2000mg.

A single can of tuna, over 7000mg of lysine!

I could keep going. But the fact is if you eat a couple of portions of almost any kind of quality protein every day (which most people already do), you’re getting plenty of lysine already.

And I seriously doubt that taking one or two extra grams of lysine will provide any extra benefits beyond those you’re already getting from eating protein daily (which you ARE doing, right?).

Plus, there may be a few problems if you go overboard with the lysine…

The side effects of lysine

Amino acids aren’t dangerous. At least, not when consumed in normal amounts, like that found in your diet.

But if you’re popping lysine capsules like candy on a daily basis, you might want to be careful and keep an eye out for any side effects.

Because after all, too much of anything can be poison (heck, you can even die from drinking too much water…).

Here’s a (non-exhaustive) list of potential side effects you can experience if you take too much lysine:

Diarrhea. If you swallow too many lysine capsules you may experience some pretty nasty cramping and “bowel evacuation”. Not fun.

Drug interactions. Apparently, lysine can interfere with the action of certain drugs and antibiotics. This is probably something you should talk to your doctor about if you take prescription drugs. Because you  don’t want to risk something potentially much worse than a little old cold sore. If you’re worried about blood pressure though, don’t. There is no evidence to suggest it increases blood pressure.

Allergies to lysine. Some people experience allergic style symptoms when taking lysine supplements. Of course, this is something you’ll notice right away if it affects you. And if it does, stop (duh!).

Gallstones. Taking too much lysine has been reported to potentially lead to the formation of gallstones in the gallbladder. Gallstones are symptomless, until they are. And when they are, you’ll notice: sudden and intense abdominal pain, back pain, nausea and vomiting. This is probably the scariest of all lysine side effects.

Of course, you shouldn’t worry about any of these side effects. You’re probably not at risk unless you take MASSIVE amounts of lysine all day, every day for a long, long time.

What’s that? You still want to try lysine for your cold sores? Here’s a few things to keep in mind.

I think you can guess that I’m not a supporter of taking lysine for treating or preventing cold sores. I know for a fact that there are MUCH more effective ways to fight off the damn herpes virus.

But who I’m I to tell you not to try? Who knows, maybe it’ll work. And I’m not going to tell you to stop doing something that works for you.

Still, keep the following points in mind when you do start taking lysine.

How much lysine do you have to take to prevent cold sores from coming back?

The general consensus is that you need to take between 1 to 3 grams of lysine supplements every day to see any beneficial effect on the recurrence rate of cold sores.

Again, how much you need to take personally has more to do with how much healthy protein (i.e. high quality meat) you eat on a daily basis. And, the specific dose is something you’ll have to test and work out for yourself.

However, if you’re taking 3 grams daily and still don’t see an improvement in the frequency of your cold sore outbreaks, I wouldn’t go over that 3 gram threshold (what with some potentially dangerous side effects). If that doesn’t work, try something else.

How long do you have to take lysine before seeing an improvement in symptoms? Well, that’s hard to say. It depends on too many factors (diet, lifestyle, etc.). But if you’re not seeing any improvement in the first 2 to 3 months, I’d throw in the towel.

How much lysine should you take during an impending or active cold sore outbreak?

Aha! This is where lysine gets just a tad interesting.

As you should now know after reading this, if lysine has any effect whatsoever on cold sores, it is while the herpes virus is actively replicating (i.e. DURING an active outbreak, i.e. when you get that tingling feeling or when the blisters are starting to form).

Why? Because the best evidence we have is that lysine may compete with arginine during the replication process of the herpes virus.

So in theory, if you can drown the herpes virus in lysine, you lower it’s odds of getting access to the arginine it needs (again, this isn’t proven beyond all doubt, but since lysine is so cheap (you can get some for under 10 dollars on Amazon) it could be worth a try).

But to really shift the balance of lysine/arginine competition in favor of lysine, you need to positively FLOOD your body with the stuff WHILE the virus is actively replicating, all day long.

What does that look like (WARNING: The following is my own personal hypothesis. Consult your doctor before taking random advice from a stranger like me on the internet.)?

Well, I’d suggest taking a large dose of lysine 3 times a day. I’d try taking 2 or 3 grams of lysine 3 times a day, so as to keep your lysine levels high all throughout the day.

Or another way you could do this is taking 1 gram every hour all throughout the day.

That way you never let up and the herpes virus practically never gets a chance to recover.

Of course, if you’re going to take that much lysine, be very aware of any unpleasant side effects and stop at the first sign of trouble.

What about lip balms and creams that contain lysine? Do they work?

True, supplements aren’t the only way to use lysine against cold sores. There are creams and lip balms that contain lysine.

Given that the best evidence we have is that lysine interferes with the replication process, applying lysine directly at the infection site isn’t a terrible idea. After all, if lysine works, how you get it there shouldn’t matter.

But, there isn’t much in the way of evidence supporting the effectiveness of lysine creams or balms outside of self-reported anecdotal evidence. And just like for supplements, for every happy ending, there’s someone else for whom it didn’t do jack.

So what’s the verdict on lysine, yay or nay?

Based on what I’ve discovered researching the relationship between lysine and cold sores, I still don’t really believe that it’s very useful. The evidence just doesn’t support it. Heck, even the anecdotal evidence is split down the middle.

At best, lysine “maybe perhaps could” be useful in large doses to keep serum levels high during an outbreak, or an impending outbreak. Still, there’s no evidence to support that either, apart from my personal untested, harebrained hypothesis (although I would be super interested to see a legit scientific study look into that…).

But as far as taking a gram or two of lysine daily in the hopes of stopping cold sores from coming back? I just don’t see it (and neither does the science). Especially if your diet already contains a healthy amount of animal protein.

Also, let’s not forget that lysine is but one of 8 essential amino acids. If you are lacking lysine to the point of suffering through symptoms of lysine deficiency, odds are you’re not eating enough animal protein. And if you’re not eating enough animal protein, odds are you’re also deficient in other essential amino acids (which all play pretty important roles in your body; they’re “essential” for a reason…).

Plus, the bigger question is whether or not lysine is more effective than taking an anti-viral like acyclovir. And as far as that fight goes, acyclovir wins by a landslide. So why would you bother with lysine when there are more effective treatment options out there?

Look, at the very best lysine messes with the replication process of the herpes virus. What it doesn’t do is prevent the virus from reactivating in the first place (nor does acyclovir, or most other cold sore treatments for that matter).

And I’ve said it before and I’ll say it again: if you want to truly prevent cold sores from coming back, you have to stop the herpes virus from waking up entirely. That way it’s literally impossible for it trigger a cold sore outbreak.

And it turns out, you don’t even need a picogram of lysine to do that.

If you want to learn the secrets of keeping the herpes virus in a deep “coma”, make sure to sign up to our daily newsletter.


Chris “the Cold Sore Killer” Mueller

Discover how to *block cold sores at the very source, without antivirals or strict diet rules. Sign up to read daily email tips and download the first chapter of the “Cold Sore Control” outbreak prevention system for free right now…
By signing up, I agree to receive the Incarsoreate newsletter by email and I understand that I will receive daily promotional emails. Our Privacy Policy.
Chris "the Cold Sore Killer" Mueller