BACKGROUND: Chlorhexidine is an effective antimicrobial agent commonly used in UK hospitals, primarily for skin decontamination. Recent UK infection control guidelines recommend the use of 2% chlorhexidine solution in specific clinical settings, thus increasing chlorhexidine use by health care workers (HCWs). Chlorhexidine has been widely reported to cause IgE-mediated allergic reactions (from urticaria and angioedema to anaphylaxis) among patients undergoing surgery/invasive procedures. Despite its widespread use in health care settings, there are no reports of clinically confirmed occupational IgE-mediated chlorhexidine allergy. AIMS: To identify cases of chlorhexidine allergy among health care workers. METHODS: A questionnaire was distributed among HCWs in wards and operating theatres at a UK district general hospital to raise awareness of potential chlorhexidine allergy and to invite those with possible clinical allergy to come forward for further testing. Diagnosis was based on an appropriate clinical history with positive serum-specific IgE to chlorhexidine and/or positive skin prick testing. RESULTS: Four cases of occupational IgE-mediated allergy to chlorhexidine were identified. CONCLUSIONS: Despite its excellent antimicrobial properties, chlorhexidine is an occupational allergen. We suggest that chlorhexidine allergy be included in the differential diagnosis of HCWs presenting with work-related allergic symptoms. Increased awareness and easier access to chlorhexidine-specific IgE serological testing should facilitate early diagnosis of affected HCWs, allowing appropriate avoidance measures to be instigated--thus reducing the risk of potentially severe allergic reactions in the future.