👉 Histamine is a protein that is released from certain cells in the body. These cells produce hormones called histamine, which are produced when the immune system detects an attack on its own tissues or organs. Histamine helps the immune system to fight off infections and other threats by causing the release of chemicals into the bloodstream. The exact mechanism by which histamine works is not fully understood, but it is believed that it acts as a chemical messenger that helps to signal the body's response to an attack.