What do the states mean?+
- Solid: well studied, and it works.
- Half-there: the science is still forming.
- A ghost: almost no real studies.
- Hollow: well studied, and it does not work.
- A cord: the pair itself has been tested together.
- Air: nobody has ever tested this pair.
The full scoring method: How we score
L-lysine benefits: where the science stands
For cold sores: no.
Cold sores is what most people take L-lysine for, and the strongest evidence says it does not help: a combined review covering 32 trials found no real difference. As of August 2026, the verdicts on this page rest on evidence from 34 trials, drawn from the strongest research among the 892 papers on PubMed that mention L-lysine. Every claim is checked below.
892 papers on PubMed · evidence from 34 trials
Claim by claim
- Cold soresWell studied, and it does not work. The biggest review covered 32 trials.
- Immunity and coldsThe science is still forming. Results lean positive, but there is not much yet.
Pairs people ask about
The two sources we read
- 2010Randomized trial · 271 people · moderate benefit for immunity and coldssource
- 2015Meta-analysis · pools 32 trials, 2,640 people · no clear effect on cold soressource
Chosen as the strongest evidence out of 892 papers on PubMed. Every row links to its paper.
Fair questions
Does L-lysine work?+
For cold sores, the strongest evidence says no. The biggest review covered 32 trials.
Is L-lysine safe?+
No caution is recorded on this page. That is not a safety guarantee; the studies we read were not safety trials.
Why only 2 sources, when PubMed lists 892?+
The 892 is every paper that mentions L-lysine in any way: animal studies, blood measurements, papers where it is a side note. The strongest sources are combined reviews, and each one already gathers every trial its authors could find. Our 2 cover 34 trials between them, and every one is linked above. Both counts are measured, not estimated.