[Multiple hypersensitivity versus multiple intolerance to drugs]

In everyday practice, many patients experience reactions to substances from different drug families. Multiple Drug Hypersensitivity Syndrome (MDHS) and Multiple Drug Intolerance Syndrome (MDIS) both involve reactions to several unrelated drugs but differ in pathophysiology and clinical presentation. Rare and immune-mediated, MDHS involves T lymphocytes and presents with severe delayed exanthems, eosinophilia, and moderate hepatic cytolysis triggered by at least two chemically distinct drugs. In contrast, MDIS is a diagnosis of exclusion, characterized by adverse reactions-often pseudoallergic and immediate-to three or more unrelated drugs, occurring upon separate exposures with negative allergy tests.