Lysine supplementation together with a low arginine diet is purported to reduce cold sores.  The basis is that herpes virus proteins are said to be high in arginine and lysine is a competitive inhibitor of arginine. 

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               The best review of data on lysine that we can find is Mailoo et al.  It appears that the evidence suggests lysine has no effect on duration or severity of a single oral or genital herpes episode but when taken daily for prevention of outbreaks at doses of more than 1 gram per day, preferably over 3 grams per day, together with a low arginine diet, it may reduce the number of outbreaks. 

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               Our recommendation would be that if you take it that you take 3 grams lysine per day and limit arginine in your diet.  Unfortunately, limiting arginine seems difficult and probably unadvisable since it is found in all sources of protein, including dairy, nuts, legumes, fish, poultry, and red meat. 

 

References:

Mailoo VJ, Rampes S. Lysine for Herpes Simplex Prophylaxis: A Review of the Evidence. Integr Med (Encinitas). 2017 Jun;16(3):42-46. PMID: 30881246; PMCID: PMC6419779. 

www.ncbi.nlm.nih.gov/pmc/articles/PMC6419779