Chlorhexidine can cause severe immediate-type allergic reactions such as urticaria, anaphylactic shock or, even, cardiac arrest. We report the case of a patient who developed perioperative anaphylactic shock caused by chlorhexidine 1 year after a postoperative urticarial reaction, which was assumed not to be significant at the time. This case highlights the importance of identifying mild allergy symptoms after exposure to chlorhexidine at the pre-anaesthetic assessment to prevent more severe allergic reactions in future.