Failure of lysine in frequently recurrent herpes simplex infection. Treatment and prophylaxis.

Lysine has been claimed to be effective in the treatment and prevention of episodes of recurrent herpes simplex (HS) infection. We carried out a double-blind, placebo-controlled trial of oral lysine hydrochloride therapy (400 mg, three times a day) in a group of 21 patients in good general health with a history of frequently recurring infection. Using our measures of episode frequency, duration, and severity, we were unable to detect any substantial benefit of lysine therapy either as a treatment for episodes in progress or as a prophylactic drug for the prevention of recurrences. We conclude that it is unlikely that lysine improves frequently recurrent HS infections in the majority of patients.