Does Lysine Work for Cold Sores? Here’s What Studies SayDoes Lysine Work for Cold Sores? Here’s What Studies Say - GoodRx (2024)

Cold sores can be a real pain in the mouth. And it can be hard to predict how big they will get or how long they will last. While no cure exists for cold sores, there are treatments that can help them go away faster — and prevent them from coming back. Lysine supplementation is one of these treatments that may help by interfering with the virus that causes cold sores.

What is lysine?

Lysine is an essential amino acid. Amino acids make up proteins in the body. Lysine is known as an “essential” amino acid because the body doesn’t make it naturally. Instead, you get lysine from the foods you eat. Lysine is important for many different bodily functions, like wound healing and the absorption of minerals like calcium.

Scientists think that it combats cold sores by blocking the production of another amino acid called arginine. The virus that causes cold sores — herpes simplex virus (HSV) — needs arginine to reproduce.

Lysine may also prevent the absorption of arginine in the intestine. This prevents a person’s body from absorbing it, which slows or prevents the replication and growth of HSV.

Lysine comes as a cream that you can apply directly to a cold sore. It’s also available as an oral supplement and in chewable and powder forms. Most of the existing studies — and all the ones mentioned in this article — have looked at the oral supplement.

Do lysine supplements actually help with cold sores?

Lysine may help prevent and treat cold sores, but research is limited. Some studies show that regularly taking lysine can help prevent outbreaks of cold sores. Others show that it can both prevent cold sores and help them go away sooner.

One study shows that lysine lessens symptoms, reduces healing time, and prevents cold sores from returning. Another small study found that people who took 1,000 mg of oral lysine a day had smaller cold sores than usual during an outbreak. But it’s worth noting that these are older studies, and newer research is limited.

There’s no cure for HSV, so taking lysine doesn’t get rid of the virus completely. This means that if you get a cold sore, you might still get outbreaks even if you take lysine.

How fast does lysine work on cold sores?

More research is needed to know how fast lysine works on cold sores. But a couple studies have tried to answer this question.

One study compared adults who took lysine for an outbreak to those who didn’t use it. Cold sores completely resolved in 3 days for almost half of the people in the lysine group. And nearly all of them saw complete resolution by day 6. But healing time took up to 21 days for people who didn’t use lysine.

A larger study surveyed over 1,500 people with cold sores. Of those who did not take lysine, 90% reported that healing took 6 to 15 days. Among people who did take lysine, 83% said their lesions healed within 5 days.

How much lysine should you take for cold sores?

There is no standardized dosage of lysine. Some studies have used 300 mg of lysine a day, while others have looked at the effects of 3,000 mg of lysine a day.

In general, dosages range from 500 mg to 1,000 mg daily by mouth to prevent outbreaks. For active outbreaks, higher doses, like 3,000 mg (3 g), may be appropriate for a short period of time.

Some experts suggest that lysine is safe at dosages up to 6,000 mg (6 g) daily. But most research recommends no more than 3 g daily for a short period of time for active outbreaks.

Instructions for over-the-counter lysine cream say that a person can apply it as often as every 2 hours. But there’s no firm research to support that the cream definitely works.

While lysine is generally safe at the above doses, some people may experience unwanted side effects.

What are there risks of taking a lysine supplement?

Common side effects of a lysine supplement may include:

• Nausea

• Abdominal pain

• Cramps

• Diarrhea

• Kidney problems

• Gallstones

Some people may want to avoid it completely because of side effects or safety concerns.

Who should not take lysine?

You should not take lysine if you:

• Are pregnant or breastfeeding: There isn’t enough research to know if lysine is safe for women who are pregnant or breastfeeding.

• Take calcium supplements: Lysine increases how much calcium your body absorbs. Too much calcium can lead to muscle pain, weakness, bone pain, and other symptoms.

• Have gallstones: High doses of lysine can cause gallstones to form. If you have a history of gallstones, it’s best to avoid lysine.

People should also avoid lysine if they have a condition that leads to lower levels of arginine, or if they currently have a wound that is healing. This includes people who have:

• Kidney disease

• Sickle cell disease

• Recent surgery

• Recent trauma or injury

As with any supplement, it’s always a good idea to talk with your provider before taking lysine. They can check to see if it’s safe for you, or if there are any potential interactions with your other medications.