Histidine is an essential amino acid that is significant in the growth and repair  of tissues. It is important for the maintenance  of the myelin sheaths , which protect nerve cells , and is needed for the production of both red and white blood cells. Histidine  also protects the body from radiation damage, helps lower blood pressure, aids in removing heavy metals from the system, and may help in the prevention of AIDS. 

Histidine levels that are too high may lead to stress and even schizophrenia; people with schizophrenia have been found to have high levels histidine in their bodies. Inadequate levels of histidine may contribute to rheumatoid arthritis and may be associated with nerve deafness. Methionine has the  ability to lower histidine levels.