Determination of serum mast cell tryptase (MCT) is becoming more widely used in diagnosing allergic reactions involving mast cells. It can help evaluate the allergenic effects of drugs administered during anesthesia and the perioperative period. Until now, data about the role of tryptase in the body has not been clarified yet. Patients with elevated MCT levels should undergo further testing to find out the causative agent of a potential allergic reaction. Patients with normal tryptase concentration should also undergo further diagnosis if they manifest clinical symptoms of a severe anaphylactic reaction.