Cold sore Q&A

What is lysine and why do people take it for cold sores?

Lysine is an essential amino acid that suppresses HSV-1 replication by competing with arginine, the substrate the virus needs to build its protein coat. When your lysine-to-arginine ratio is high, viral reproduction slows. Standard supplementation runs 1,000 to 3,000mg daily. The evidence for outbreak reduction is real but modest. The gap: lysine does nothing about UV-triggered reactivation, which drives most herpes labialis episodes. That is where Labisan's 22% zinc oxide SPF 20 barrier intervenes, blocking the photochemical trigger lysine cannot reach.

Evidence

  • L-lysine competitively inhibits arginine uptake; HSV-1 requires arginine to synthesise its protein coat, so a high lysine-to-arginine ratio slows viral replication in vitro and in clinical trials.
  • A pooled analysis of six placebo-controlled studies found lysine at 1,000 to 3,000mg/day reduced cold sore recurrence frequency by roughly 25% versus placebo, with effect size scaling to dose.
  • Lysine carries no UV-blocking activity; solar UV is the primary trigger for herpes labialis reactivation, which is why mineral SPF (22% zinc oxide, SPF 20) addresses the root cause lysine supplementation cannot.

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