L-Lysine

What Is L-Lysine?

L-Lysine is an essential amino acid — one the body cannot make and must obtain from diet — and a required building block for protein and collagen synthesis. It is best known as a supplement for reducing the frequency of herpes simplex (cold sore) outbreaks, a use rooted in lysine’s antagonistic relationship with arginine in viral replication. The cold-sore evidence is genuinely mixed: some prophylaxis trials are positive, while trials treating active lesions have generally failed.

Evidence

The rationale for lysine in herpes is that a high lysine-to-arginine ratio suppresses herpes simplex virus replication in cell culture. In humans the clinical picture is inconsistent. An early multicentre study of supplementary lysine reported accelerated recovery and reduced recurrence of herpes simplex infection ^{1Reference 1Griffith RS et al. · 1978Clinical trialA multicentered study of lysine therapy in Herpes simplex infection — clinical trialView study →}, and a later placebo-controlled prophylaxis study found fewer recurrences on 1 g/day of lysine ^{2Reference 2Thein DJ · 1984Clinical trialLysine as a prophylactic agent in the treatment of recurrent herpes simplex labialis — clinical trialView study →}. However, a 2017 review of the collected evidence concluded that trials treating active sores generally showed no significant benefit, and that support for prophylaxis was mixed rather than convincing ^{3Reference 3Mailoo VJ · 2017ReviewLysine for herpes simplex prophylaxis: a review of the evidence — reviewView study →}. Lysine’s role as a substrate for collagen and general protein synthesis is basic biochemistry, but claims that supplemental lysine meaningfully improves collagen or connective-tissue outcomes in well-nourished people were not backed by a citable clinical trial in this quick pass and should be treated as unproven.

Dosage & Safety

Cold-sore prophylaxis trials commonly used around 1 g/day, with some active-treatment studies going higher (roughly 1–3 g/day) ^{2Reference 2Thein DJ · 1984Clinical trialLysine as a prophylactic agent in the treatment of recurrent herpes simplex labialis — clinical trialView study →3Reference 3Mailoo VJ · 2017ReviewLysine for herpes simplex prophylaxis: a review of the evidence — reviewView study →}; these ranges are informational and not a personal recommendation. Lysine is generally well tolerated and its acute toxicity appears low, but formal upper-limit data, drug interactions, and pregnancy/lactation safety were not established or fully assessed in this pass. Very high chronic intake has been associated with gastrointestinal upset in some reports.

References

1. Griffith RS, Norins AL, Kagan C. (1978). A multicentered study of lysine therapy in Herpes simplex infection — clinical trial. Dermatologica. https://pubmed.ncbi.nlm.nih.gov/640102/
2. Thein DJ, Hurt WC. (1984). Lysine as a prophylactic agent in the treatment of recurrent herpes simplex labialis — clinical trial. Oral Surg Oral Med Oral Pathol. https://pubmed.ncbi.nlm.nih.gov/6438572/
3. Mailoo VJ, Rampes S. (2017). Lysine for herpes simplex prophylaxis: a review of the evidence — review. Integr Med (Encinitas). https://pmc.ncbi.nlm.nih.gov/articles/PMC6419779/