Final answer:
Systemic mast cell degranulation accounts for 60% of unexpected drug induced allergic reactions in the perioperative period.
Step-by-step explanation:
60% of unexpected drug induced allergic reactions in the perioperative period are accounted for by systemic mast cell degranulation. This occurs when an allergen is eaten, injected, or inhaled, causing the release of histamine and other inflammatory chemicals. These chemical mediators can lead to severe allergic reactions, including anaphylactic shock, which can be fatal if untreated.