L-Lysine
Commonly used for
Immune Support
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What is it? / Overview
Lysine competitively antagonizes arginine, an amino acid HSV needs to replicate and build its capsid proteins -- a plausible mechanism for reducing outbreak frequency that has not translated into reliable benefit in the one controlled trial available. Well tolerated at typical doses, so low-harm even if the benefit is modest or absent for a given user.
How is it used? / Administration
Form: L-lysine (essential amino acid), as L-lysine HCl
Typical dose studied: ~1,000 mg/day for prevention; up to ~1,000 mg 2-3x/day used for active outbreaks in traditional protocols
Timing: Daily for suppression, on an empty stomach; often paired with limiting high-arginine foods
For anyone with frequent or severe outbreaks, oral antivirals are the better-evidenced first-line option -- lysine is reasonable as a low-risk adjunct, not a replacement for that conversation with a doctor.
How well does it work? / Evidence
? Emerging / limited evidence
Who should avoid it?
Avoid with: Chronic kidney disease (Stage 3, 4, or 5) — NOT on dialysis; End-stage liver disease / Cirrhosis
Already taking it? Be honest about the evidence here: the popular cold-sore-suppression use rests largely on an old, uncontrolled 1983 survey and a plausible mechanism, while the one controlled trial captured in a Cochrane review found no significant preventive effect. Oral antivirals (acyclovir/valacyclovir) are the evidence-based option for suppression if outbreaks are frequent or severe -- reasonable to continue lysine given its low-risk profile, but don't oversell the benefit.
Research & references
Chi CC et al. (2015). Interventions for Prevention of Herpes Simplex Labialis (Cold Sores on the Lips). Cochrane Database of Systematic Reviews. Pedrazini MC et al. (2022). L-Lysine: Its Antagonism With L-Arginine in Controlling Viral Infection. Narrative Literature Review. British Journal of Clinical Pharmacology.
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