Lysine is an essential amino acid and is therefore one of the eight amino acids that our bodies can not make, so we are completely reliant on our diets to provide sufficient lysine. It is used by the body in a number of ways and, particularly in the formation of collagen, the most abundant protein in the body. Practitioners frequently recommend this particular amino acid during an attack of cold sores as it has been shown to inhibit the replication of the Herpes Simplex (Type I) virus. We require 2-3g a day of lysine and it is most abundant in animal based foodstuffs such as meat. Vegetables and vegetable proteins are not particularly high in lysine, and so some experts believe that vegetarian and vegan diets may provide rather low levels of lysine. An essential amino acid found mainly in meat and dairy foods Intake maybe low levels for some vegans and vegetarians Plays an important role in collagen formation alongside proline, glycine, vitamin C and copper Works antagonistically to arginine to inhibit viral replication Lysine increases the bioavailability of iron. Lamberts uses a USP grade of L-Lysine, which is the quality used in clinical nutrition products. Some very cheap products are likely to contain animal feed-grade lysine as huge quantities are produced for agricultural use.