Test Details: Tryptase is an enzyme found mainly in mast cells. Mast cells are white blood cells that are part of the body’s immune system and become activated during allergic reactions. Blood levels of tryptase may be measured for several different purposes. Testing tryptase may be helpful: 1)To determine if a severe allergic reaction, called anaphylaxis or anaphylactic shock, has recently occurred 2)To diagnose mast cell disorders, rare conditions in which there are either too many mast cells in the body or the mast cells are abnormally reactive 3)To monitor patients with mast cell disorders to see whether their condition is stable or worsening