Chlorhexidine: a hidden and often undeclared allergen

Abstract Chlorhexidine (1:6-di-4’-chlorophenyldiguanidohexane) has been a widely used antiseptic since its introduction in 1954. Alongside alexidine, it belongs to the group of cationic bisbiguanides with a broad spectrum of activity. Due to its diverse applications—such as in skin and mucous membrane disinfection, with use in mouthwashes, wound antiseptics, or catheterization—chlorhexidine has been an integral part of healthcare and beyond as an antiseptic for decades. Despite its generally good tolerability, chlorhexidine is also a potent allergen that can trigger both type I and type IV hypersensitivity reactions. In the following article, we provide an overview of anaphylactic reactions caused by chlorhexidine.