Reviews the biochemical nature and structure of lysine. Mechanism of action of lysine in suppressing herpes labialis outbreaks. Reviews historical clinical trials and studies utilizing lysine supplementation in the management of herpes labialis. Be familiar with reported effective dosages of lysine in herpes labialis suppression. Pharmacology of lysine therapy. Contraindications for lysine supplementation. Potential deleterious interactions of lysine with prescription antibiotics.