Tryptase is an enzyme released from mast cells along with histamine and other chemicals when they are activated as part of both a normal immune response and allergic (hypersensitivity) reactions. A tryptase test measures the amount of tryptase in the blood. However, because of the life-threatening nature of anaphylaxis, its diagnosis is not made solely based on this test. Currently, there is no single definitive biological marker for diagnosing anaphylaxis. A tryptase level measurement may be helpful in suspected cases. The tryptase test should be interpreted by comparing blood samples taken 60-90 minutes after the onset of anaphylaxis symptoms and again 24-48 hours after the complete resolution of symptoms.