Skip to content
Back to Cold Sores

ingestible · for cold sores

L-Lysine

Reviewed by the Nimbera editorial team · Last updated May 2026

Griffith et al. (1987, PMID 3115841) RCT (n=52) found lysine 1,000 mg three times daily for 6 months reduced HSV recurrences by a mean of 2.4 episodes (p<0.05) and shortened healing time. However, a 2015 Cochrane review (PMID 26252373) found no evidence of efficacy for lysine in HSL prevention across pooled trials. Evidence is mixed and effect sizes are modest.$8-$15 per month

How to use

Take 1,000 mg of L-lysine monohydrochloride once daily as a preventive dose between outbreaks. At the first sign of a tingling prodrome, some practitioners recommend 1,000 mg three times daily for the outbreak duration.

How it works

Lysine competes with arginine (an amino acid required for HSV replication) for intestinal absorption and cellular uptake. Elevating the lysine-to-arginine ratio in cells is thought to impair viral replication. Avoiding high-arginine foods (nuts, chocolate) may enhance this effect.

Where to buy

Pharmacies, health food stores, and online; widely available as L-lysine monohydrochloride tablets or capsules.

Typical cost: $8-$15 per month

Safety notes

Evidence is mixed - the Cochrane review found no definitive benefit at the population level. High doses (>3,000 mg/day long-term) may affect cholesterol levels and kidney function. Not recommended in children without medical advice. Do not use lysine as a substitute for prescription antivirals if outbreaks are frequent or severe.

Drug & supplement interactions

  • Always tell your doctor or pharmacist about any supplements you take.
  • Interactions can occur with prescription medications, blood thinners, and immunosuppressants.
  • Herbal remedies can affect how the body absorbs or metabolises drugs.
  • Check drugs.com interactions checker before starting.

Clinical source

Griffith RS et al., Success of L-lysine therapy in frequently recurrent herpes simplex infection, Dermatologica, 1987

This information is compiled from primary clinical literature and is for informational purposes only. It is not a substitute for professional medical advice. Read our full disclaimer.