What is L-lysine for?

L-lysine is a substance found in beans, yogurt, meats and animal proteins that is taken in supplement form or applied topically as a treatment and preventative therapy for herpes infections and cold sores, according to Drugs.com. L-lysine also helps to increase calcium absorption, which may benefit individuals with osteoporosis.

When taken or applied as directed, L-lysine is considered a possible safe treatment for most individuals, according to WebMD; however, L-lysine may cause stomach upset and diarrhea in children. Individuals with kidney disease should consult with a physician prior to taking L-lysine as the supplement has been associated with one reported case of kidney disease.