L-lysine is an amino acid that supports antibody, hormone and enzyme production, as well as providing antioxidant properties. L-lysine competes with L-arginine that is required for the replication of upper respiration pathogens. L-lysine also supports collagen formation and tissue repair to promote healthy skin. Available in a delicious chew, L-Lysine by Pet Naturals® is perfect for multi-cat households, boarding, kittens, and senior cats.