L-Histidine (Standard) is a reference standard for research and analysis in studies involving L-Histidine. L-Histidine (L-(-)-Histidine) is a semi-essential amino acid (children should obtain it from food) needed in humans for growth and tissue repair, L-Histidine is important for maintenance of myelin sheaths that protect nerve cells and is metabolized to the neurotransmitter histamine. Histamines play many roles in immunity, gastric secretion, and sexual functions. L-Histidine is also required for blood cell manufacture and protects tissues against damage caused by radiation and heavy metals.