Histidine is considered a non-essential amino acid for adults, however dietary sources (meat, fish, & dairy products) of histidine probably account for most of the total found in the body. Histidine is used by the body to build proteins, & is also used as the precursor of the neurotransmitter, histamine, which is released by the body during allergic reactions such as hay fever. Histidine is involved with the regulation & utilisation of several essential trace minerals in the body including zinc, copper, manganese & iron. It is also used in the formation of red & white blood cells. & is involved in maintaining the myelin sheaths that protect nerve cells. Lamberts L-Histidine is a pure, free-form amino acid that is ready to be absorbed by the body without needing to be broken down by digestive enzymes. Each capsule provides a full 500mg of L-Histidine HCl. As with most free form amino acids, L-Histidine absorption is best when taken between meals without food & without accompanying minerals. A white powder in a clear hard shell capsule. Each capsule delivers: L-Histidine HCI 500mg Encapsulated with: Capsule Shell (Gelatin), Cellulose, Magnesium Stearate, Silicon Dioxide Disintegration Time Less than 30 minutes..