Cold sores are tiny blisters that appear either in the mouth or on the lips. Some people use lysine, which is an essential amino acid, to help treat or prevent cold sores, but does it work?

A virus causes cold sores, so a doctor will typically prescribe antiviral medications to help treat an outbreak. They may also recommend that a person uses lysine, which is an amino acid found in some foods, to help treat the virus.

Lysine is essential for many bodily functions, including helping with calcium absorption and collagen formation. Most people will consume enough lysine in their diet for their body’s basic needs.

However, people looking to use lysine to help treat cold sores will probably need to take a supplement to boost their lysine intake. Read on to learn more about how lysine affects cold sores.

Does lysine help treat cold sores?

Woman applying lip balm which contains lysine that helps with cold sores
Lysine ointments and lip balms can help to prevent the growth of the herpes simplex virus.

Lysine may help to slow down or prevent the growth of the herpes simplex virus type 1 (HSV-1), which is responsible for cold sores.

HSV-1 requires arginine, which is another amino acid, to grow. Lysine helps prevent the body from absorbing arginine, making it difficult for HSV-1 to grow and reproduce.

According to the American Academy of Dermatology, more than 50 percent of people aged 14 to 49 carry the virus. Lysine may slow or stop the lifecycle of HSV-1, but it cannot cure the person of the virus. Once a person has contracted the virus, they will always have it.

Sources of lysine

Lysine is an essential amino acid. The human body does not naturally produce lysine, so a person needs to get it from their diet or take a supplement.

Foods containing lysine include:

  • pork
  • turkey
  • chicken
  • beef
  • eggs
  • yogurt
  • Parmesan cheese
  • soybeans
  • spirulina
  • sardines
  • codfish

People can also use an ointment containing lysine to help treat cold sores. People can apply the ointment directly to the sore according to the instructions on the packaging until the infection clears.

Lysine ointments and lip balms are available in pharmacies and online.


Most doctors agree that lysine is safe to use either as a cream or oral supplement. It is important that a person follows the instructions on the packaging when using lysine products.

Too much lysine can cause side effects, including:

Pregnant and breastfeeding women should not take lysine supplements unless their doctor recommends it.

Other treatments

For people with healthy immune systems, cold sores typically clear up within 2 weeks.

The typical treatment for cold sores is antiviral medications. Doctors most commonly prescribe:

  • valacyclovir (Valtrex)
  • acyclovir (Zovirax)

These medications are available as topical ointments, pills, or injections. Some people also use them to help prevent future outbreaks of cold sores.


how to not get sick wash hands
A person should wash their hands after touching a cold sore.

Cold sores are highly contagious. A person is contagious even when undergoing treatment and remains contagious until all the blisters have scabbed over. People with weakened immune systems are particularly vulnerable to infection.

A person with one or more active cold sore can help prevent passing on the virus by:

  • avoiding intimate contact with others
  • not kissing anyone
  • avoiding close contact with anyone with a weakened immune system, such as babies
  • not sharing beverages or food
  • not sharing personal grooming items, such as razors, toothbrushes, or lip balms
  • washing their hands after touching a cold sore or the medication
  • washing their hands regularly throughout the day
  • not touching the cold sores throughout the day

Taking antiviral medications can help prevent outbreaks of cold sores.

Lysine supplements can also help prevent future cold sores from developing. A person should speak to a doctor or pharmacist about dosage and use.

Lysine supplements are available in health food stores, pharmacies, and online.


Lysine is not a cure for cold sores, but it may help prevent and shorten the duration of an outbreak.

A person should continue to take any antiviral medications a doctor prescribes for their cold sores. Those interested in adding lysine supplements to their routine should speak to their doctor beforehand.